自律小屋构造函数
如果不显示声明构造函数，则会调用默认构造函数。默认构造函数没有参数
dart
class Point {
int x, y;
Point(this.x, this.y);
@override
String toString() {
return '$x, $y';
}
}
final p = Point(1, 2);
print(p);初始化列表
构造函数中的:表示一个初始化器，它先于构造函数执行，用来初始化实例变量
dart
class Point {
int x, y;
Map position1, position2;
Point(this.x, this.y)
: position1 = {'x': x, 'y': y},
position2 = {'x': x + 10, 'y': y + 10} {
print('In Point(): ($x, $y, $position1, $position2)');
}
@override
String toString() {
return '$x, $y, $position1, $position2';
}
}命名构造函数
dart
class Point {
int x, y;
Map position1, position2;
Point.fromJson(Map json)
: x = json['x'],
y = json['y'],
position1 = {'x': json['x'], 'y': json['y']},
position2 = {'x': json['x'] * 2, 'y': json['y'] * 2} {
print('In Point.fromJson(): ($x, $y, $position1, $position2)');
}
@override
String toString() {
return '$x, $y, $position1, $position2';
}
}重定向构造函数
dart
class Point {
int x, y;
Map position1, position2;
Point(this.x, this.y)
: position1 = {'x': x, 'y': y},
position2 = {'x': x + 10, 'y': y + 10} {
print('In Point(): ($x, $y, $position1, $position2)');
}
Point.fromJson(Map json) : this(json['x'], json['y']);
@override
String toString() {
return '$x, $y, $position1, $position2';
}
}callable
dart
class Phone {
call(String phone) {
print('phone number is $phone');
}
}
var phone = Phone();
phone('911');