Flutter Dependency Injection

What is Dependency Injection?

It is important to follow the best possible practices when building up a production-level application in order to make the application more powerful and stable; dependency injections are one of the techniques which can be used to achieve this. Simply put, dependency injection is a way to inject an instance of one class into another. It also offers shared instances which are highly helpful in state management by organizing the code at a higher level.

Drawbacks of the constructor injection technique:

It is difficult to pass the constructor down the multiple widgets.
Difficult to create shared instances.

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Why Dependency Injection?

To reduce coupling between classes thus achieving greater reusability of code.
To create a class independent of its dependencies.
It also reduces the risk that you have to change a class just because one of its dependencies changed.

How to achieve dependency injection in flutter?

We can use dependency injection in a flutter with GetX.
Let’s continue the further process to start the implementation of dependency injection in a flutter.

Installing

dependencies:
  get: ^4.6.5

1 2	dependencies: get: ^4.6.5

Usage

Step-1 To inject the object of the class use “Get.put”

When this method is used, the dependency will load immediately and can be used directly by implementing the code given below:

class FirstScreen extends StatelessWidget 
{
  // Controller dependency injected
  Controller controller = Get.put(Controller());

  @override
  Widget build(BuildContext context) 
  {
    // It can be used directly
    return Text(controller.name); 
  }
}

class FirstScreen extends StatelessWidget

{

// Controller dependency injected

Controller controller = Get.put(Controller());

@override

Widget build(BuildContext context)

{

// It can be used directly

return Text(controller.name);

}

we can also use the tag property to store multiple instances of the same class.

class ScreenOne extends StatelessWidget {
  Controller controllerOne = Get.put(Controller(), tag: 'tagOne');
  Controller controllerTwo = Get.put(Controller(), tag: 'tagTwo');

}

class ScreenOne extends StatelessWidget {

Controller controllerOne = Get.put(Controller(), tag: 'tagOne');

Controller controllerTwo = Get.put(Controller(), tag: 'tagTwo');

}

Step-2 To find the controller in our application lifecycle after injecting use “Get.find”

We can also use the Get.find tag property in case of multiple shared instances which need to be updated individually. Use the code mentioned below to achieve this:

class ScreenTwo extends StatelessWidget {
  Controller controller = Get.find();
  Controller controllerOne = Get.find(tag: 'tagOne');
  Controller controllerTwo = Get.find(tag: 'tagTwo');

}

class ScreenTwo extends StatelessWidget {

Controller controller = Get.find();

Controller controllerOne = Get.find(tag: 'tagOne');

Controller controllerTwo = Get.find(tag: 'tagTwo');

}

The dependencies will be deleted if the route used Get.put is removed from the navigation stack. Hence, we need to prevent this and keep the dependencies in the internal memory for the entire app session using permanent properties as shown below:

Get.put(Controller(), permanent: true);

1	Get.put(Controller(), permanent: true);

As a result of “permanent: true”, you will overcome the above route stack issue.

Advantages Of GetX Dependency Injection Techniques:

The injection is available globally.
Instance tracking is automatic in this technique.
It is possible to register against interfaces.
We can implement the compact setup code.

Disadvantages Of GetX Dependency Injection Techniques:

Disposing is not a top priority of dependency injection techniques.
It follows loose coding guidelines which make development difficult.
It is a global object which makes things a bit complicated.

Conclusion

In this article, we have gone through the implementation of GetX dependency injection techniques. This technique offers an efficient and steady way of managing dependency injection. Hope this article has made the topic more comprehensive for you.

Thank you so much for reading! If you want to read more about the topic then click here.

Happy Coding!! 🙂

Vipul Chauhan 27 April 2023

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