Calling an async method from a constructor in Dart

Probably the best way to handle this is with a factory function, which calls a private constructor.

In Dart, private methods start with an underscore, and “additional” constructors require a name in the form ClassName.constructorName, since Dart doesn’t support function overloading. This means that private constructors require a name, which starts with an underscore (MyComponent._create in the below example).

import 'dart:async';
import 'dart:io';

class MyComponent{
  /// Private constructor
  MyComponent._create() {
    print("_create() (private constructor)");

    // Do most of your initialization here, that's what a constructor is for
    //...
  }

  /// Public factory
  static Future<MyComponent> create() async {
    print("create() (public factory)");

    // Call the private constructor
    var component = MyComponent._create();

    // Do initialization that requires async
    //await component._complexAsyncInit();

    // Return the fully initialized object
    return component;
  }
}

void main() async {
  var c = await MyComponent.create();

  print("done");
}

This way, it’s impossible to accidentally create an improperly initialized object out of the class. The only available constructor is private, so the only way to create an object is with the factory, which performs proper initialization.