We'll take a look at two more Dart features that are useful in some situations but aren't crucial when using Dart, and you'll probably not use them on a daily basis.
Dart lets us overload its default behavior when using standard operators such as ==, +, -, [], or []=. A typical use case is when using 2D/3D vectors:
class Vector {
int x, y;
Vector(this.x, this.y);
operator ==(Vector v) => this.x == v.x && this.y == v.y;
operator +(Vector v) => new Vector(this.x + v.x, this.y + v.y);
operator -(Vector v) => new Vector(this.x - v.x, this.y - v.y);
}We can use unit testing to check whether operators work as expected:
var v1 = new Vector(5, 3); var v2 = new Vector(7, 2); Vector v3 = v1 + v2; expect(v3.x, 12); expect(v3.y, 5); expect((v1 - v2) == new Vector(-2, 1), isTrue); var v6 = new Vector(3, 5); expect(v1 == v6, isFalse);
Unlike JavaScript, there's no === operator (three equal signs) in Dart that compares variables...