Flutter Mixins Vs. Inheritance: Choosing the Right Approach for Code Reuse

As a Flutter developer, have you ever come across the dilemma of choosing between Mixins Vs. Inheritance for code reuse in Dart?

Well, that's what we are going to discuss today.

Though both approaches have their advantages and disadvantages, the selection always depends on your project requirements.  

Mixins are a powerful tool for reusing code in Dart programming. They allow you to add functionality to multiple classes without creating a deep class hierarchy. On the other hand, inheritance is an effective way to reuse code between classes that are related to each other.

In this blog, we will explore the concept of mixins in detail,  how it is used, the difference between mixins and inheritance, when to use mixins and when to use inheritance, the simple implementation example of Flutter mixins and finally we will take a look at the best practices of using it in Flutter.  

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What is the use of Mixin in Dart? 

Mixins in Dart are a way to reuse code across multiple classes. They provide a mechanism for adding additional functionality to a class without the need for an inheritance, this helps to avoid the diamond problem of multiple inheritances. 

By using a “mixin” keyword with your “mixin” class, you can easily add the desired functionality to the superclass or regular class. You can also integrate interfaces or abstract classes with mixins, making them a top choice among developers.

Mixins allow you to encapsulate commonly used code and easily apply it to different classes, promoting code reusability and maintainability. By using mixins, you can enhance the capabilities of your Flutter widgets and share functionality efficiently.

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What is the difference between Mixin and Inheritance in Dart?

Mixins in Dart allow you to reuse code across unrelated classes. They provide a way to share functionality without creating an "is-a" relationship between classes. On the other hand, inheritance in Dart creates a parent-child relationship between classes. 

Subclasses inherit properties and methods from the superclass, allowing for specialization and extension of functionality. Inheritance provides a hierarchical structure, where subclasses are categorized and organized based on their relationships with the superclass.

Mixins do not introduce a new type hierarchy and can be applied to multiple classes simultaneously, while inheritance creates a new type hierarchy with a clear parent-child relationship. Mixins don't have constructors and cannot be instantiated directly, whereas subclasses inherit constructors from the superclass and can be instantiated independently.

The following table of comparison gives a complete overview of key differences between Mixins and Inheritance in Dart.

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When to use Mixins and when to use Interfaces in Dart?

Flutter Mixins and Inheritance are two powerful mechanisms for code reuse. While both offer benefits, they also come with their strengths and limitations. The decision between mixins and inheritance depends on the specific requirements of a project.

Here are some guidelines for when to use mixins and when to use inheritance in Dart language:

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1. Use mixins when you need to reuse code between unrelated classes

For example, you could create a Loggable mixin that contains methods for logging messages. This mixin could then be used by any class that needs to be able to log messages.

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2. Use inheritance when you need to reuse code between related classes. 

For example, you could create a Car class that inherits from a Vehicle class. This would allow you to reuse the code that is common to all cars, such as the ability to accelerate, brake, and turn.

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3. Use mixins when you need to add functionality to a class without affecting its inheritance hierarchy. 

For example, you could create a Flyable mixin that contains methods for flying. This mixin could then be used by any class that needs to be able to fly, regardless of its inheritance hierarchy.

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4. Use inheritance when you need to create a subclass that inherits from multiple superclasses.

Dart does not support multiple inheritance, but you can use mixins to achieve a similar effect. For example, you could create a Car class that inherits from a Vehicle class and a Loggable mixin. This would allow the Car class to reuse the code from both the Vehicle class and the Loggable mixin.

Ultimately, the best choice for a particular project will depend on the specific requirements. If you are not sure which approach to use, it is always best to consult with an experienced Flutter developer.

There are some additional considerations when choosing between mixins and inheritance such as Compile time, Code Reuse, and Flexibility.

• Compile time: Mixins are compiled at runtime, which can make debugging more difficult. Inheritance is compiled at compile time, which can make debugging easier.
• Code reuse: Mixins can be used to reuse code between unrelated classes, while inheritance can only be used to reuse code between related classes.

Flexibility: Mixins are more flexible than inheritance because they do not require the classes to be related.

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The implementation of Mixins in the Flutter application

Implementing Mixins in Flutter has multiple advantages such as code reusability, flexibility, and consistency.

Let's consider an example where we have a mixin named TextMixin that defines common text styles:

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1     mixin TextMixin {
2      TextStyle headingTextStyle() {
3        return TextStyle(
4          fontSize: 24.0,
5          fontWeight: FontWeight.bold,
6          color: Colors.black,
7        );
8      }
9    
10      TextStyle bodyTextStyle() {
11        return TextStyle(
12          fontSize: 16.0,
13          color: Colors.grey,
14        );
15      }
16    }
17    
18    class MyWidget extends StatelessWidget with TextMixin {
19      @override
20      Widget build(BuildContext context) {
21        return Column(
22          children: [
23            Text(
24              'Welcome',
25              style: headingTextStyle(),
26            ),
27            Text(
28              'Lorem ipsum dolor sit amet',
29              style: bodyTextStyle(),
30            ),
31          ],
32        );
33      }
34    }
35    
36    void main() {
37      runApp(
38        MaterialApp(
39          home: Scaffold(
40            body: Center(
41              child: MyWidget(),
42            ),
43          ),
44        ),
45      );
46    }
47     

In this example, the TextMixin defines two text styles: headingTextStyle and bodyTextStyle. The MyWidget class uses the mixin by including it using the “with” keyword for TextMixin.

Inside the build method, we apply the mixin's text styles to two Text widgets: one for the heading and another for the body text. By using the mixin, we avoid duplicating the text style code and can easily maintain and update the styles across multiple widgets.

The use of mixins in this example promotes code reusability, separation of concerns, and easy consistency in text styling throughout the app. If you need to update the text styles, you can make changes in the TextMixin, and the updates will automatically propagate to all widgets using that mixin.

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Best practices for using Mixins in Flutter app development

When using mixins in a Dart Flutter app, it's important to follow certain best practices to ensure clean and maintainable code. Take a look at the below recommended practices for using mixins effectively.

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1. Name mixins with the "Mixin" suffix: 

To improve code readability and make it clear that a class is a mixin, follow the convention of naming mixins with the "Mixin" suffix. For example, if you have a mixin for logging functionality, name it LoggingMixin.

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2. Document the purpose and usage of mixins: 

Provide clear and concise documentation for your mixins, explaining their purpose and how they should be used. This will help other developers understand their intended functionality and proper implementation.

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3. Keep mixins focused and cohesive: 

Aim to create mixins with a single, well-defined responsibility. This promotes code reusability and makes it easier to understand and maintain the mixin. Avoid creating overly large or complex mixins that try to handle multiple unrelated functionalities.

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4. Prefer mixins over inheritance for unrelated code sharing: 

Use mixins when you want to share code across unrelated classes. Mixins allow for code reuse without creating an inheritance relationship, providing more flexibility and decoupling between classes.

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5. Be cautious with mixin order: 

The order in which mixins are applied can affect the behavior and interactions of the class. If multiple mixins modify the same behavior, ensure they are applied in the correct order to achieve the desired outcome. Consider the potential conflicts or dependencies between mixins and order them accordingly.

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6. Use mixins for code that enhances existing classes: 

Mixins are particularly useful for adding additional functionality or modifying the behavior of existing classes. This allows you to extend the capabilities of a class without modifying its inheritance hierarchy.

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7. Avoid relying on the mixin-specific state: 

Mixins should generally not introduce their own state that can't be accessed or controlled by the class using the mixin. Instead, focus on providing reusable methods or behavior that can be utilized by the class.

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8. Prefer composition over mixins for complex behaviors:

If the desired behavior involves complex composition or multiple interacting components, consider using composition (i.e., combining multiple classes) instead of relying solely on mixins. The composition can offer more explicit control and better organization in such scenarios.

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9. Test mixins independently: 

When using mixins, it's a good practice to test them independently to ensure their functionality works as expected. Isolate the mixin and write unit tests specifically for it to verify its behavior in different scenarios.

By adhering to these best practices, you can effectively utilize mixins in your Dart Flutter app, promoting code reusability, maintainability, and readability.

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Let's create a Flutter app with reusable code with Mixins using DhiWise Flutter Builder

In conclusion, while both mixins and inheritance serve the purpose of code reuse, understanding when to use each approach is crucial for efficient Flutter app development. Mixins offer flexibility and modularity, allowing developers to add functionality without changing the class hierarchy.

However, it's essential to be cautious while using mixins as they can lead to code duplication and method conflicts. On the other hand, inheritance offers a clear hierarchy and is suitable for creating objects with a similar structure.

So, if you are building a Flutter application and are concerned about code reuse it's a good idea to use mixins. Also, if you're looking forward to making your app development more sophisticated, faster, and effortless try DhiWise - A new edge web and mobile app development platform for developers.

Its Flutter Builder has everything to make your app development process more efficient and effortless, from design to code and UI customization to API integration and more. Mixins in DhiWise Flutter Builder are useful when applying a group of CSS properties to multiple elements across different pages. They are easy to modify enabling you to reflect the changes to the entire app quickly. 

Start building your next Flutter app with DhiWise today!