Dependency Management

Get has a simple and powerful dependency manager that allows you to retrieve the same class as your Bloc or Controller with just 1 lines of code, no Provider context, no inheritedWidget:

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

Instead of instantiating your class within the class you are using, you are instantiating it within the Get instance, which will make it available throughout your App. So you can use your controller (or Bloc class) normally

Instancing methods

The methods and it’s configurable parameters are:

Get.put()

The most common way of inserting a dependency. Good for the controllers of your views for example.

Get.put<SomeClass>(SomeClass());
Get.put<LoginController>(LoginController(), permanent: true);
Get.put<ListItemController>(ListItemController, tag: "some unique string");

This is all options you can set when using put:

Get.put<S>(
  // mandatory: the class that you want to get to save, like a controller or anything
  // note: "S" means that it can be a class of any type
  S dependency

  // optional: this is for when you want multiple classess that are of the same type
  // since you normally get a class by using Get.find<Controller>(),
  // you need to use tag to tell which instance you need
  // must be unique string
  String tag,

  // optional: by default, get will dispose instances after they are not used anymore (example,
  // the controller of a view that is closed), but you might need that the instance
  // to be kept there throughout the entire app, like an instance of sharedPreferences or something
  // so you use this
  // defaults to false
  bool permanent = false,

  // optional: allows you after using an abstract class in a test, replace it with another one and follow the test.
  // defaults to false
  bool overrideAbstract = false,

  // optional: allows you to create the dependency using function instead of the dependency itself.
  // this one is not commonly used
  InstanceBuilderCallback<S> builder,
)

Get.lazyPut

It is possible to lazyLoad a dependency so that it will be instantiated only when is used. Very useful for computational expensive classes or if you want to instantiate several classes in just one place (like in a Bindings class) and you know you will not gonna use that class at that time.

/// ApiMock will only be called when someone uses Get.find<ApiMock> for the first time
Get.lazyPut<ApiMock>(() => ApiMock());

Get.lazyPut<FirebaseAuth>(
  () {
    // ... some logic if needed
    return FirebaseAuth();
  },
  tag: Math.random().toString(),
  fenix: true
)

Get.lazyPut<Controller>( () => Controller() )

This is all options you can set when using lazyPut:

Get.lazyPut<S>(
  // mandatory: a method that will be executed when your class is called for the first time
  InstanceBuilderCallback builder,
  
  // optional: same as Get.put(), it is used for when you want multiple different instance of a same class
  // must be unique
  String tag,

  // optional: It is similar to "permanent", the difference is that the instance is discarded when
  // is not being used, but when it's use is needed again, Get will recreate the instance
  // just the same as "SmartManagement.keepFactory" in the bindings api
  // defaults to false
  bool fenix = false
  
)

Get.putAsync

If you want to register an asynchronous instance, you can use Get.putAsync:

Get.putAsync<SharedPreferences>(() async {
  final prefs = await SharedPreferences.getInstance();
  await prefs.setInt('counter', 12345);
  return prefs;
});

Get.putAsync<YourAsyncClass>( () async => await YourAsyncClass() )

This is all options you can set when using putAsync:

Get.putAsync<S>(

  // mandatory: an async method that will be executed to instantiate your class
  AsyncInstanceBuilderCallback<S> builder,

  // optional: same as Get.put(), it is used for when you want multiple different instance of a same class
  // must be unique
  String tag,

  // optional: same as in Get.put(), used when you need to maintain that instance alive in the entire app
  // defaults to false
  bool permanent = false
)

Get.create

This one is tricky. A detailed explanation of what this is and the differences between the other one can be found on Differences between methods: section

Get.Create<SomeClass>(() => SomeClass());
Get.Create<LoginController>(() => LoginController());

This is all options you can set when using create:

Get.create<S>(
  // required: a function that returns a class that will be "fabricated" every
  // time `Get.find()` is called
  // Example: Get.create<YourClass>(() => YourClass())
  FcBuilderFunc<S> builder,

  // optional: just like Get.put(), but it is used when you need multiple instances
  // of a of a same class
  // Useful in case you have a list that each item need it's own controller
  // needs to be a unique string. Just change from tag to name
  String name,

  // optional: just like int`Get.put()`, it is for when you need to keep the
  // instance alive thoughout the entire app. The difference is in Get.create
  // permanent is true by default
  bool permanent = true

Using instantiated methods/classes

Imagine that you have navigated through numerous routes, and you need a data that was left behind in your controller, you would need a state manager combined with the Provider or Get_it, correct? Not with Get. You just need to ask Get to “find” for your controller, you don’t need any additional dependencies:

final controller = Get.find<Controller>();
// OR
Controller controller = Get.find();

// Yes, it looks like Magic, Get will find your controller, and will deliver it to you.
// You can have 1 million controllers instantiated, Get will always give you the right controller.

And then you will be able to recover your controller data that was obtained back there:

Text(controller.textFromApi);

Since the returned value is a normal class, you can do anything you want:

int count = Get.find<SharedPreferences>().getInt('counter');
print(count); // out: 12345

To remove an instance of Get:

Get.delete<Controller>(); //usually you don't need to do this because GetX already delete unused controllers

Specifying an alternate instance

A currently inserted instance can be replaced with a similar or extended class instance by using the replace or lazyReplace method. This can then be retrieved by using the original class.

abstract class BaseClass {}
class ParentClass extends BaseClass {}

class ChildClass extends ParentClass {
  bool isChild = true;
}


Get.put<BaseClass>(ParentClass());

Get.replace<BaseClass>(ChildClass());

final instance = Get.find<BaseClass>();
print(instance is ChildClass); //true


class OtherClass extends BaseClass {}
Get.lazyReplace<BaseClass>(() => OtherClass());

final instance = Get.find<BaseClass>();
print(instance is ChildClass); // false
print(instance is OtherClass); //true

Differences between methods

First, let’s of the fenix of Get.lazyPut and the permanent of the other methods.

The fundamental difference between permanent and fenix is how you want to store your instances.

Reinforcing: by default, GetX deletes instances when they are not in use. It means that: If screen 1 has controller 1 and screen 2 has controller 2 and you remove the first route from stack, (like if you use Get.off() or Get.offNamed()) the controller 1 lost its use so it will be erased.

But if you want to opt for using permanent:true, then the controller will not be lost in this transition - which is very useful for services that you want to keep alive throughout the entire application.

fenix in the other hand is for services that you don’t worry in losing between screen changes, but when you need that service, you expect that it is alive. So basically, it will dispose the unused controller/service/class, but when you need it, it will “recreate from the ashes” a new instance.

Proceeding with the differences between methods:

Bindings

One of the great differentials of this package, perhaps, is the possibility of full integration of the routes, state manager and dependency manager. When a route is removed from the Stack, all controllers, variables, and instances of objects related to it are removed from memory. If you are using streams or timers, they will be closed automatically, and you don’t have to worry about any of that. In version 2.10 Get completely implemented the Bindings API. Now you no longer need to use the init method. You don’t even have to type your controllers if you don’t want to. You can start your controllers and services in the appropriate place for that. The Binding class is a class that will decouple dependency injection, while “binding” routes to the state manager and dependency manager. This allows Get to know which screen is being displayed when a particular controller is used and to know where and how to dispose of it. In addition, the Binding class will allow you to have SmartManager configuration control. You can configure the dependencies to be arranged when removing a route from the stack, or when the widget that used it is laid out, or neither. You will have intelligent dependency management working for you, but even so, you can configure it as you wish.

Bindings class

class HomeBinding implements Bindings {}

Your IDE will automatically ask you to override the “dependencies” method, and you just need to click on the lamp, override the method, and insert all the classes you are going to use on that route:

class HomeBinding implements Bindings {
  @override
  void dependencies() {
    Get.lazyPut<HomeController>(() => HomeController());
    Get.put<Service>(()=> Api());
  }
}

class DetailsBinding implements Bindings {
  @override
  void dependencies() {
    Get.lazyPut<DetailsController>(() => DetailsController());
  }
}

Now you just need to inform your route, that you will use that binding to make the connection between route manager, dependencies and states.

getPages: [
  GetPage(
    name: '/',
    page: () => HomeView(),
    binding: HomeBinding(),
  ),
  GetPage(
    name: '/details',
    page: () => DetailsView(),
    binding: DetailsBinding(),
  ),
];

Get.to(Home(), binding: HomeBinding());
Get.to(DetailsView(), binding: DetailsBinding())

There, you don’t have to worry about memory management of your application anymore, Get will do it for you.

The Binding class is called when a route is called, you can create an “initialBinding in your GetMaterialApp to insert all the dependencies that will be created.

GetMaterialApp(
  initialBinding: SampleBind(),
  home: Home(),
);

BindingsBuilder

The default way of creating a binding is by creating a class that implements Bindings. But alternatively, you can use BindingsBuilder callback so that you can simply use a function to instantiate whatever you desire.

Example:

getPages: [
  GetPage(
    name: '/',
    page: () => HomeView(),
    binding: BindingsBuilder(() {
      Get.lazyPut<ControllerX>(() => ControllerX());
      Get.put<Service>(()=> Api());
    }),
  ),
  GetPage(
    name: '/details',
    page: () => DetailsView(),
    binding: BindingsBuilder(() {
      Get.lazyPut<DetailsController>(() => DetailsController());
    }),
  ),
];

That way you can avoid to create one Binding class for each route making this even simpler.

Both ways of doing work perfectly fine and we want you to use what most suit your tastes.

SmartManagement

GetX by default disposes unused controllers from memory, even if a failure occurs and a widget that uses it is not properly disposed. This is what is called the full mode of dependency management. But if you want to change the way GetX controls the disposal of classes, you have SmartManagement class that you can set different behaviors.

How to change

If you want to change this config (which you usually don’t need) this is the way:

void main () {
  runApp(
    GetMaterialApp(
      smartManagement: SmartManagement.onlyBuilder //here
      home: Home(),
    )
  )
}

SmartManagement.full

It is the default one. Dispose classes that are not being used and were not set to be permanent. In the majority of the cases you will want to keep this config untouched. If you new to GetX then don’t change this.

SmartManagement.onlyBuilder

With this option, only controllers started in init: or loaded into a Binding with Get.lazyPut() will be disposed.

If you use Get.put() or Get.putAsync() or any other approach, SmartManagement will not have permissions to exclude this dependency.

With the default behavior, even widgets instantiated with “Get.put” will be removed, unlike SmartManagement.onlyBuilder.

SmartManagement.keepFactory

Just like SmartManagement.full, it will remove it’s dependencies when it’s not being used anymore. However, it will keep their factory, which means it will recreate the dependency if you need that instance again.

How bindings work under the hood

Bindings creates transitory factories, which are created the moment you click to go to another screen, and will be destroyed as soon as the screen-changing animation happens. This happens so fast that the analyzer will not even be able to register it. When you navigate to this screen again, a new temporary factory will be called, so this is preferable to using SmartManagement.keepFactory, but if you don’t want to create Bindings, or want to keep all your dependencies on the same Binding, it will certainly help you. Factories take up little memory, they don’t hold instances, but a function with the “shape” of that class you want. This has a very low cost in memory, but since the purpose of this lib is to get the maximum performance possible using the minimum resources, Get removes even the factories by default. Use whichever is most convenient for you.

Notes