Dart initializing formal parameters

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Dart initializing formal parameters

The pattern of assigning a constructor argument to an instance variable is so common that Dart decided to add a special syntax for it.

Dart called this feature Initializing formal parameters.

To use Initializing formal parameters feature, we have to do two things:

1. Declare a constructor by creating a function with the same name as its class.
2. List all instance variables as constructor arguments.
   • Argument name must match an instance variable.
   • Prefix those argument with this keyword.

Here is how it looks:

class Shape {
  double x;
  double y;
  double width;
  double height;

  Shape({
    required this.x,
    required this.y,
    required this.width,
    required this.height,
  });
}

This will assign all arguments to respective instance variables.