Lets go to the Python interactive interpreter and see how it works: The new design of Factory Method allows the application to introduce new features by adding new classes, as opposed to changing existing ones. The missing piece is that SerializerFactory has to change to include the support for new formats. The more you develop, the more code you will write. Unless you have a very basic creator that will never change in the future, you want to implement it as a class and not a function. Imagine an application that needs to convert a Song object into its string representation using a specified format. JSON and YAML are very similar formats, so you can reuse most of the implementation of JsonSerializer and overwrite .to_str() to complete the implementation. The architecture is similar to what you'd get with Flask's Blueprint. In the above code, we have designed a class called Apple that has color as an attribute. Lets use the Python interactive shell to see how the code works: You create a song object and a serializer, and you convert the song to its string representation by using the .serialize() method. It specifies the required parameters and ignores any additional parameters provided through **_ignored. A good solution is to specialize a general purpose implementation to provide an interface that is concrete to the application context. Constructing related objects from external data: Imagine an application that needs to retrieve employee information from a database or other external source. Design Pattern - Factory Pattern - tutorialspoint.com Lets look at the below code. Each pattern is given a name, a problem description, a design solution, and an explanation of the consequences of using it. This pattern is also used as an example in the Flask repository itself, so maybe this is the best one. Factory Method in Python / Design Patterns - refactoring.guru But the problem is that the functions such as init and getColor are cluttering the namespace and also we wont be able to reuse the functionality. Here is how I initialized the Celery instance in the single file application: celery = Celery(app.name, broker=app.config['CELERY_BROKER_URL']) celery.conf.update(app.config) So this is a big problem, as I'm using app all over the place here. Each service is initialized with a different set of parameters. Factory Design Pattern in C# with Examples - Dot Net Tutorials The pattern avoids modifying existing code to support new requirements. So what should we do? Hosting a Dedicated Terraria Server on AWS, How to represent a list of different JSON objects using enums in Swift, Day 20CS Fundamentals DecemberIntro to Virtual Machines and Virtualization, How To Change Flutter Popup Menu Width? {. Then, the builders are registered with the instance. The interface implementation might look something like this: Note: The example above doesnt implement a full Serializer interface, but it should be good enough for our purposes and to demonstrate Factory Method. The creator object happens to be the class name of the concrete Serializer. But this doesnt help at all. The rule above tells us it should not be part of the class. In this method, objects are created without revealing the logic to the client. Python Factories for Scalable, Reusable, and Elegant Code In Python, I use Flask to create APIs as I find this is easy to use, yet very powerful. The Factory Pattern is an Interface that defers the creation of the final object to a subclass. Finally, the application implements the concept of a local music service where the music collection is stored locally. And, for OpenId service, the parameters are service name and email address. In this series of articles we are going to take a look at several design patters (creational, behavioral, structural), what are they and how we can implement them in Python. Features It uses FastAPI framework for API development. The answer is wsgi.py that acts as the entry point. Not all situations allow us to use a default .__init__() to create and initialize the objects. Is using this app object is the best way? Factory Pattern also has another variation, usually known as Abstract Factory Pattern aka . With this approach, the application code is simplified, making it more reusable and easier to maintain. Unless you have a very high percentage of code coverage with your unit tests, this is not a change that you should be doing. The FDP is based on a single function written to handle object creation. This is important because changing existing code can introduce changes in behavior or subtle bugs. In the original example, you implemented the creator as a function. You can execute the same set of instructions in the Python interactive interpreter to verify that the application behavior has not changed: You create a song and a serializer, and use the serializer to convert the song to its string representation specifying a format. This pattern restricts the number of objects that can be created from a class to one single object that will often-times be shared globally in an application. These patterns are selected based on the requirement analysis. The "Factory Method" pattern is a poor fit for Python. The desired interface is an object or a function that takes a Song object and returns a string representation. Writing code in comment? Sending Asynchronous Emails Through Celery To test this setup I converted the thread based email sending function to use Celery. Factory Design Pattern in Python - javatpoint Factory Method is to creating objects as Template Method is to implementing an algorithm. 369 3 9. Now let us understand the factory method with the help of an example: Lets look at the class diagram considering the example of ride-sharing. Designing a class factory using the class keyword is nothing but creating a function that holds a class. I want to be able to write to a mongodb as part of a background task but I receive the following error: RuntimeError: Working outside of application context. Classes can provide additional interfaces to add functionality, and they can be derived to customize behavior. Lets see the below code: Using type we can create classes dynamically. When the string representation for a format changes (plain JSON vs JSON API): The .serialize() method will have to change if the desired string representation for a format changes because the representation is hard-coded in the .serialize() method implementation. By using our site, you This method evaluates the value of format and returns the matching serialization function: Note: The ._get_serializer() method does not call the concrete implementation, and it just returns the function object itself. Replacing complex logical code: Complex logical structures in the format if/elif/else are hard to maintain because new logical paths are needed as requirements change. Hi, I'm Isaac. Lets take a look at the code I use in my current project below. Demystifying Flask's Application Factory And the Application Context I build, lead, and mentor software development teams, and for the past few years I've been focusing on cloud services and back-end applications using Python among other languages. It provides one of the best ways to create an object. Unlike django, there isnt a start project command that will automatically generate all the files you need along with the suggested structure. The local service is simpler, but it doesnt match the initialization interface of the others. The single responsibility principle states that a module, a class, or even a method should have a single, well-defined responsibility. This means a common initialization interface for each service implementation is not possible or recommended. create_app is the application factory function. Lets look into the code to understand it better. Many guides use this single file app to showcase the simplicity and the lightness of the framework. The factory design pattern (FDP) falls under the category of creational design patterns. The flask-execute plugin supports the application factory pattern out of the box: from flask import Flask from flask_execute import Celery celery = Celery () app = Flask (__name__) celery.init_app (app) Share. At the same time, other users want to integrate with Pandora. It's suitable for developing small to medium sized API oriented micro-services. We can easily add new types of products without disturbing the existing client code. but what about the software developers of your startup. Ideally, the design should support adding serialization for new objects by implementing new classes without requiring changes to the existing implementation. The code above might not seem hard to read or understand, but wait till you see the final code in this section! That interface will be implemented in a Builder. A new instance is created every time the service is requested because there is no slow authorization process. In our implementation the drawing framework is the client and the shapes are the products. Here, objects are created without exposing the logic to the client, and for creating the new type of object, the client uses the same common interface. Creating a new service instance is done very quickly, so a new instance can be created every time the user wants to access the music collection. The application can allow the user to select an option that identifies the concrete algorithm. The creator returns the concrete implementation according to the value of the parameter to the client, and the client uses the provided object to complete its task. We first start by creating our parent class of APIConnector as an abstract base class with just one function for . Abstract Factory Method - Python Design Patterns, Accessing Web Resources using Factory Method Design Pattern in Python, Implementing Web Crawler using Abstract Factory Design Pattern in Python, Composite Method - Python Design Patterns, Decorator Method - Python Design Patterns, Prototype Method - Python Design Patterns, Flyweight Method - Python Design Patterns, Singleton Method - Python Design Patterns, Chain of Responsibility - Python Design Patterns, Python Programming Foundation -Self Paced Course, Complete Interview Preparation- Self Paced Course, Data Structures & Algorithms- Self Paced Course. This authorization process is very slow, and it should only be performed once, so the application wants to keep the initialized service object around and use it every time it needs to communicate with Spotify. Design Patterns is the most essential part of Software Engineering, as they provide the general repeatable solution to a commonly occurring problem in software design. If we use the first type of code I mentioned, there will be bound to be problems in the long run. In those languages, the Factory Method serves as an awkward but necessary escape route. Love to hear from you here at Real Python. This problem is easily solved with the new design because SerializerFactory is a class. Commenting Tips: The most useful comments are those written with the goal of learning from or helping out other students. The serializable parameter refers to another abstract interface that should be implemented on any object type you want to serialize. In the application factory function the application is available, so configuration works exactly as in the single file case. This allows the Builder objects to specify the parameters they need and ignore the rest in no particular order. Factory Method can be used to solve a wide range of problems. Where should we put our models, routes, app, tests, etc? The pattern removes complex logical code that is hard to maintain, and replaces it with a design that is reusable and extensible. Lets look at the implementation of the SpotifyService and SpotifyServiceBuilder: Note: The music service interface defines a .test_connection() method, which should be enough for demonstration purposes. The functionality of classapple method is to return the color of the apple. A Factory Method will receive information about a required object, instantiate it and return the object of the specified type. The example defines the Serializer interface to be an object that implements the following methods or functions: This interface is implemented by the concrete classes JsonSerializer and XmlSerializer. Configure your app with environment variable and any settings that you want to change from the default. Imagine you are having your own startup which provides ridesharing in different parts of the country. Shape.java public interface Shape { void draw(); } Step 2 Create concrete classes implementing the same interface. Using the Factory method, we have the best ways to create an object. But if you move the creation of this object into a function, you can then create multiple instances of this app later. By using our site, you In the following snippet, we create an Abstract product called Animal. ; celery.config_from_object(app.config, namespace="CELERY") indicates that all Celery-related configuration keys should be written in uppercase and prefixed with CELERY_. Curated by the Real Python team. It is one of the powerful patterns in Python. generate link and share the link here. The application may store an identifier representing the type of employee in the record and then use Factory Method to create each concrete Employee object from the rest of the information on the record. Unsubscribe any time. Finally, lets take a look at the local service implementation: The LocalService just requires a location where the collection is stored to initialize the LocalService. This is possible because all the Serializer classes provide a default .__init__() to initialize the instances. It is a relatively simple solution that allows us to verify the functionality of all the Factory Method components. The Builder object has all the logic to create and initialize a service instance. Factory Method is a Creational Design Pattern that allows an interface or a class to create an object, but lets subclasses decide which class or object to instantiate. Still, the current implementation is specifically targeted to the serialization problem above, and it is not reusable in other contexts. It provides a method to register a Builder based on a key value and a method to create the concrete object instances based on the key. They usually represent some of the best practices adopted by experienced object-oriented software developers. Please use ide.geeksforgeeks.org, It separates the process of creating an object from the code that depends on the interface of the object. Application Setup Flask Documentation (1.1.x) You will implement a Builder object for each of the supported services. Step 2: Choose the type of reCaptcha. The method takes the song object as a parameter, as well as a string value representing the format you want. This example presents several challenges. Abstract Factory Design Pattern in Python Coming back to the definition of the Abstract Factory Pattern: Through the Abstract Factory Pattern, we define interfaces to create families of related objects without specifying their concrete classes. generate link and share the link here. But this is where the problem comes in. It also keeps the service instance around, so the authorization only happens once. Factory Method should be used in every situation where an application (client) depends on an interface (product) to perform a task and there are multiple concrete implementations of that interface. They all define a client that depends on a common interface known as the product. Class Factories: A powerful pattern in Python - GeeksforGeeks These things prevents us from throwing the app objects around. In factory pattern, objects are created without exposing the logic to client and referring to the newly created object using a common interface. Lets start by looking at the application configuration: The config dictionary contains all the values required to initialize each of the services. class CreditCardFactory. Love podcasts or audiobooks? Supporting multiple implementations of the same feature: An image processing application needs to transform a satellite image from one coordinate system to another, but there are multiple algorithms with different levels of accuracy to perform the transformation. The format is used to identify the concrete implementation of the Serializer and is resolved by the factory object. In the above example, we did not use any pattern and the application is working fine. My __init__.pyfile is: # # __init__.py # from flask import Flask from flask_pymongo import PyMongo from flask_mail import Mail from flask_login import LoginManager mail = Mail() mongo = PyMongo() 20122022 RealPython Newsletter Podcast YouTube Twitter Facebook Instagram PythonTutorials Search Privacy Policy Energy Policy Advertise Contact Happy Pythoning! The implementation of SerializerFactory is a huge improvement from the original example. Youll often see these requirements implemented in a single function or method that contains all the logic and implementation, like in the following code: In the example above, you have a basic Song class to represent a song and a SongSerializer class that can convert a song object into its string representation according to the value of the format parameter. Factory Pattern in Python - Be A Python Dev Lets look at the below code. Once the access_code is retrieved, it creates and returns the SpotifyService instance. The interface defined is referred to as the product component. will use those values to create a concrete implementation of a music service. This is a proxy that can point to the current application. It is unknown what or how many objects will need to be created until runtime. As a matter of fact, the Song class doesnt even know the goal is to convert the data to a string. Step 1: Install Flask-Mail using the command below. The format is then registered with the factory object to make it available. This increases the risk of introducing new defects or breaking existing functionality when changes are made. The records represent employees with different roles or types: managers, office clerks, sales associates, and so on. For Spotify and Pandora, you register an instance of their corresponding builder, but for the local service, you just pass the function. The Decorator Pattern can be useful in Python code! The guides often point out each others mistakes and calls their ideas as the best practices. Using if/elif/else conditional structures makes the code harder to read, harder to understand, and harder to maintain. Any other format specified is not supported, so a ValueError exception is raised. Network, system and software engineer with true passion about technology. Flask-Application-Factory-Pattern. Factory Pattern aka Factory Method, Simple Factory is one of the most common Design Patterns out there. The factory pattern comes under the creational patterns list category. The Serializer interface is an abstract concept due to the dynamic nature of the Python language. Factory Method is a good replacement because you can put the body of each logical path into separate functions or classes with a common interface, and the creator can provide the concrete implementation. Here, we will consider two scenarios, either traditional login or using an OpenId service. Factory Method makes a design more customizable and only . The Factory Pattern method falls under a class of design patterns, object creational patterns, where the programmer's objective is to allow the client to create multiple similar instances of a class while the program achieves loose coupling which is one of the top 10 skills to be a better programmer. It is important that the creator, in this case the Object Factory, returns fully initialized objects. This was surprisingly easy to do. It provides great flexibility to support new formats and avoids modifying existing code. We can not consider the Design Patterns as the finished design that . The .get_serializer() method retrieves the registered creator and creates the desired object. Python Design Patterns - Factory - tutorialspoint.com Flask values the term flexibility so much that I find many projects that have completely different structures. But, you can note that even after setting the color of apple to Yellow and Green, the object returns the default color red. Factory Method - Refactoring and Design Patterns It makes your code more flexible and easy to maintain. This is correct, but you are dealing with existing code. The central idea in Factory Method is to provide a separate component with the responsibility to decide which concrete implementation should be used based on some specified parameter. The parameter evaluated in the conditions becomes the parameter to identify the concrete implementation. This is a minimalistic and extensible FastAPI template that incorporates factory pattern architecture with divisional folder structure. The Factory Method Pattern and Its Implementation in Python The creator decides which concrete implementation to use. Also, Heads First Design Patterns: A Brain-Friendly Guide by Eric Freeman and Elisabeth Robson provides a fun, easy-to-read explanation of design patterns. In the following sections, you will learn how to make changes to existing code without changing the behavior. Leave a comment below and let us know. Lets use the Python interactive interpreter to see the results: By implementing Factory Method using an Object Factory and providing a registration interface, you are able to support new formats without changing any of the existing application code. Based on the goal, you look for a common interface that can be used to replace each of the paths. The Definitive Guide to Celery and FastAPI - Application Factory Now, if you look at the structure I provided above carefully, which files should the factory be written? In this section, we will cover how to design class factories and the use cases of it. You can use the generator explicitly if you want, for example: gen = shapeNameGen(7) print(gen.next()) So next ( ) is the iterator method that's actually called to generate the next object, and it takes no arguments. 1 branch 0 tags. When I was first tasked to start a Flask project, I am stumped about what to do. The following example shows how to specialize ObjectFactory, providing an explicit interface to the context of the application: You derive MusicServiceProvider from ObjectFactory and expose a new method .get(service_id, **kwargs). This example is short and simplified, but it still has a lot of complexity. To create a particular concrete product object, the client might have to sub-class the creator class. Should I Quit School to be a Self-taught Software Developer? python - Flask application factory pattern with Flask-Mail - Stack Overflow Python: Factory Design pattern. The factory pattern is a Creational app = Flask(__name__, instance_relative_config=True) creates the Flask instance.. __name__ is the name of the current Python module. I wont debate on which pattern you should use. Create a class file with the name CreditCardfactory.cs and then copy and paste the following in it. It is one of the powerful patterns in Python. This avoids going through the authorization process multiple times as specified in the requirements. Thus leading to the reuse of existing code and increased flexibilty because the . The concrete implementation of the interface is identified by some parameter. There are some challenges to providing a general purpose implementation of Object Factory, and in the following sections you will look at those challenges and implement a solution that can be reused in any situation. Flask API Folder structure, Application Factory, .flaskenv, and More. The factory creates the concrete implementation of the music service based on the specified key parameter. Python Design Patterns - Quick Guide - tutorialspoint.com This means a Builder can be a function, a class, or an object that implements .__call__(). They all provide a means to identify the concrete implementation of the product, so they all can use Factory Method in their design. Objects returned by a factory method are often referred to as products. The example above requires an interface that takes a song object and returns a string. The requirements are simpler, so you dont need a Builder class. Functions are fine for very simple examples, but they dont provide too much flexibility when requirements change. Factory Pattern | Object Oriented Design In a Graphics system, depending upon the users input it can draw different shapes like rectangles, Square, Circle, etc. If you search for another guide for Flask Application Factory, you will more or less get the same file structure. Factory: Encapsulating Object Creation Python 3 Patterns, Recipes and For example, an application requires an object with a specific interface to perform its tasks. The basic requirements for the example above are that you want to serialize Song objects into their string representation. To create a new type of object, the client uses . This is where the app is created, so if your deployment requires you to point to the app object, you can find the object inside the wsgi.py file. In addition to this, we have declared a class method called classapple using the decorator @classmethod. Suppose we have created an app whose main purpose is to translate one language into another and currently our app works with 10 languages only. The best approach is to define a new type of object that provides a general interface and is responsible for the creation of a concrete service. Lets say an application wants to integrate with different music services. ; Rather than creating a new Celery instance, we used current_app so that shared tasks work as expected. Factory design pattern in Python. Design patterns: Factory pattern - Medium Therefore, the Abstract Factory Pattern delegates the creation of objects to another class. This method is used to create and initialize the concrete SpotifyService. {. When I searched How to start a Flask project almost every single guide I found shows this single file called app.py. This may lead to confusion. This files still needs to be created yes, as this is the app object itself. I'm trying to use Flask-Mailacross different files. Abstract Factory Pattern - GeeksforGeeks Flask very frequently advertise itself as a simple, lightweight framework for web development in python, which is completely true by the way. But for the ease of both developers as well as the client, we can use the factory method to create the instance depending upon the users input. Finally, the ._get_serializer() method is the creator component. A new tech publication by Start it up (https://medium.com/swlh). Since YAML is not a supported format, ValueError is raised. The patterns describe the solution to the problem, when and where to apply the solution and the consequences of the implementation. This two login scenario points to the fact that attributes of a class differ based on the login service. You'll add to it later in the tutorial, but it already does a lot. Writing code in comment? This is important because you could use this interface to provide a different kind of serializer that converts the Song information to a completely different representation if needed. Include the support for new formats and avoids modifying existing code and increased flexibilty because.! To read or understand, and replaces it with a different set of parameters start by looking at the Factory! Create and initialize the concrete implementation of a class differ based on single. Rest in no particular order the application implements the concept of a service. Functionality, and more a specified format code I use in my current project below that. To start a Flask project almost every single guide I found shows this single file case sized API micro-services. It doesnt match the initialization interface of the best way and is resolved the... Of objects to specify the parameters are service name and email address routes. Method & quot ; Factory method in their design but if you search for another for... But wait till you see the final object to a string representation using a common interface music. Initialized objects API oriented micro-services method should have a single, well-defined responsibility put! Login service available, so the authorization process multiple times as specified in above. Process multiple times as specified in the following in it created yes, as well as a string representation,. Concrete implementation of the most common design patterns: Factory pattern comes under the creational patterns category! '' > Factory design pattern ( FDP ) falls under the creational patterns category... Abstract Factory pattern aka Factory method & quot ; Factory method in their design can! Out each others mistakes and calls their ideas as the product component design pattern FDP. Not be part of the specified key parameter framework is the app object itself avoids modifying code! Site, you implemented the creator object happens to be a Self-taught software Developer Real. Reuse of existing code without changing the behavior single function written to handle object creation can use method. The records represent employees with different roles or types: managers, office clerks sales! Goal is to convert a Song object into a function that holds a class called Apple has... Those written with the name CreditCardfactory.cs and then copy and paste the following sections, you will more less! That SerializerFactory has to change to include the support for new formats and avoids modifying existing code without the! I use in my current project below database or other external source along with instance... App object itself they need and ignore the rest in no particular order most common design.. Through * * _ignored email address the._get_serializer ( ) to initialize each of the object of the one... Get the same interface a music service based on the login service current application file.. Products without disturbing the existing client code a class classes can provide additional interfaces add! Often point out each others mistakes and calls their ideas as the entry point that the... List category provides ridesharing in different parts of the powerful patterns in Python a different set of.. Not be part of the country every single guide I found shows this single file app to showcase the and. A Factory method can be used to replace each of the paths point to the existing implementation: )... < a href= '' https: //medium.com/swlh ) method should have a single written. To understand, and replaces it with a different set of parameters less get the same time, other want! Conditional structures makes the code harder to read or understand, but it doesnt the... Repository itself, so configuration works exactly as in the single file called app.py code... Are often referred to as the finished design that local service is because. How many objects will need to be a Self-taught software Developer ; s Blueprint interface! Return the color of the class architecture with divisional folder structure because all the Serializer classes provide a to! Not possible or recommended necessary escape route an OpenId service, the application can allow the user to an. In addition to this, we create an object to provide an interface that can point to problem. The local service is simpler, but wait till you see the below code: using type we can classes! Represent some of the music collection is stored locally that shared tasks work expected! An Abstract product called Animal leading to the problem, when and where to apply the to!, the more you develop, the Song object into its string representation code in case... What to do their ideas as the best ways to create a particular concrete product object, Factory! You here at Real Python login service client code create and initialize the instances are selected based on requirement. I converted the thread based email application factory pattern python function to use Flask-Mailacross different.! The service is initialized with a different set of parameters that depends on the interface is Abstract. This files still needs to retrieve employee information from a database or other external source or recommended each others and. Pattern can be useful in Python quot ; pattern is an Abstract product called Animal or many. But creating a function FDP is based on the interface defined is referred to as products Flask-Mailacross different.! Can not consider the design should support adding serialization for new objects by implementing new classes requiring! Flask-Mail using the command below void draw ( ) to create a particular concrete product,. Of SerializerFactory is a huge improvement from the default the services will more or get! Will need to be problems in the original example, we did not use any pattern the. The tutorial, but it doesnt match the initialization interface for each service implementation not. Isnt a start project command that will automatically generate all the Serializer interface is an Abstract product called Animal a. To sub-class the creator object happens to be created yes, as this the! It is important that the creator class divisional folder structure to integrate with Pandora the app object the... Client code this is possible because all the logic to create and the., there isnt a start project command that will automatically generate all the Factory design (! Requirements are simpler, but it doesnt match the initialization interface for each service is. The drawing framework is the app object itself factories and the consequences of the Serializer classes provide a to... Reuse of existing code can introduce changes in behavior or subtle bugs and on! Example, we create an Abstract base class with just one function for & quot ; Factory method components multiple! Selected based on the goal of learning from or helping out other students a huge improvement from the code might! Below code: using type we can easily add new types of products disturbing... Support for new objects by implementing new classes without requiring changes to the existing code. Too application factory pattern python flexibility when requirements change //medium.com/swlh ), routes, app, tests, etc the.... Of problems other external source design that times as specified in the example... Change to include the support for new formats /a > Therefore, the application configuration: the useful... Of objects to specify the parameters they need and ignore the rest in no particular order using. Concrete product object, the Song class doesnt even know the goal, you can then create multiple of. A database or other external source instance around, so they all a. There is no slow authorization process multiple times as specified in the original example patterns out there the of... ; s suitable for developing small to medium sized API oriented micro-services start command. Called classapple using the Decorator pattern can be used to identify the concrete Serializer not be of! Creator object happens to be the class keyword is nothing but creating a function, implemented. Since YAML is not reusable in other contexts ( FDP ) falls under the category creational... Two scenarios, either traditional login or using an OpenId service s Blueprint allows! These patterns are selected based on the specified key parameter pattern can be derived to customize.! The values required to initialize each of the Apple derived to customize behavior comes the! Short and simplified, but they dont provide too much flexibility when requirements change should... Example, we have designed a class method called classapple using the Decorator pattern can be to! Is simpler, but wait till you see the below code: application factory pattern python type we can create classes.. The concept of a class differ based on the requirement analysis and harder to understand, harder! Consequences of the best practices adopted by experienced object-oriented software developers the Factory pattern - medium < /a Therefore!, there isnt a start project command that will automatically generate all the Factory object sending function use... Original example Abstract base class with just one function for process of creating object! This app object is the creator, in this section ways to create and initialize the instances pattern also another... Simpler, so maybe this is the creator as a function that holds a class classapple method is to. Represent employees with different music services from external data: imagine an application wants integrate! Modifying existing code solution and the application is working fine oriented micro-services into their string representation using common! But it doesnt match the initialization interface for each service is requested because is. Login service be derived to customize behavior external data: imagine an application that to... Above might not seem hard to maintain, and an explanation of the services be Self-taught... Pattern you should use the category of creational design patterns as the product component interface Shape { void (! Has another variation, usually known as the entry point a subclass first type of object, it!