[英]Is it possible to define an abstract named constructor in Dart?
我正在尝试创建一个抽象类Firestorable
,它将确保子类覆盖命名的构造函数fromMap(Map<String, dynamic> map)
代码看起来像这样......
abstract class Firestorable {
/// Concrete implementations will convert their state into a
/// Firestore safe [Map<String, dynamic>] representation.
Map<String, dynamic> toMap();
/// Concrete implementations will initialize its state
/// from a [Map] provided by Firestore.
Firestorable.fromMap(Map<String, dynamic> map);
}
class WeaponRange implements Firestorable {
int effectiveRange;
int maximumRange;
WeaponRange({this.effectiveRange, this.maximumRange});
@override
WeaponRange.fromMap(Map<String, dynamic> map) {
effectiveRange = map['effectiveRange'] ?? 5;
maximumRange = map['maximumRange'] ?? effectiveRange;
}
@override
Map<String, int> toMap() {
return {
'effectiveRange': effectiveRange,
'maximumRange': maximumRange ?? effectiveRange,
};
}
}
当我这样做时,我没有收到任何错误,但是当我忽略fromMap(..)
构造函数的具体实现时,我也没有收到编译错误。
例如,以下代码将编译而不会出现任何错误:
abstract class Firestorable {
/// Concrete implementations will conver thier state into a
/// Firestore safe [Map<String, dynamic>] representation.
Map<String, dynamic> convertToMap();
/// Concrete implementations will initialize its state
/// from a [Map] provided by Firestore.
Firestorable.fromMap(Map<String, dynamic> map);
}
class WeaponRange implements Firestorable {
int effectiveRange;
int maximumRange;
WeaponRange({this.effectiveRange, this.maximumRange});
// @override
// WeaponRange.fromMap(Map<String, dynamic> map) {
// effectiveRange = map['effectiveRange'] ?? 5;
// maximumRange = map['maximumRange'] ?? effectiveRange;
// }
@override
Map<String, int> convertToMap() {
return {
'effectiveRange': effectiveRange,
'maximumRange': maximumRange ?? effectiveRange,
};
}
}
我不能定义一个抽象的命名构造函数并且让它成为一个具体类中的 require 实现吗? 如果没有,这样做的正确方法是什么?
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