Dart initializing formal parameters

⋅ 1 min read ⋅ Flutter Dart Constructor

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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;

required this.x,
required this.y,
required this.width,
required this.height,

This will assign all arguments to respective instance variables.

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