TypeScript 类：静态和继承答案

【问题标题】：TypeScript class: statics and inheritanceTypeScript 类：静态和继承
【发布时间】：2015-01-04 12:06:01
【问题描述】：

问题：

我观察到的行为是 TypeScript 的预期行为吗？
我观察到的行为是 ECMAScript 6 的预期行为吗？
是否有一种简单的方法可以返回继承层次结构来处理每个级别的“myStatic”数组？我怎么知道什么时候停止？

描述：使用 TypeScript 时，派生类和静态属性似乎有一些有趣的行为。

class MyBase {
    static myStatic = [];
}

class MyDerived extends MyBase {}

MyBase.myStatic = ['one', 'two', 'three']

class MyDerived2 extends MyBase {}

document.body.innerHTML += "<b>MyDerived.myStatic:</b>&nbsp;" + JSON.stringify(MyDerived.myStatic) + "<br/>";
document.body.innerHTML += "<b>MyDerived2.myStatic:</b>&nbsp;" + JSON.stringify(MyDerived2.myStatic) + "<br/>";

这是结果：

MyDerived.myStatic: []
MyDerived2.myStatic: ["one","two","three"]

编辑：添加说明 TypeScript 和 ECMA Script 6 之间不同行为的示例。注意：ECMA 脚本不支持静态属性，因此这些示例使用静态方法。

TypeScript 代码：

class MyBase {
  static myStatic() { return []; }
}

class MyDerived extends MyBase {}

MyBase.myStatic = () => { return ['one', 'two', 'three']; }

class MyDerived2 extends MyBase {}

document.body.innerHTML += "<b>MyDerived.myStatic:</b>&nbsp;" + JSON.stringify(MyDerived.myStatic()) + "<br/>";
document.body.innerHTML += "<b>MyDerived2.myStatic:</b>&nbsp;" + JSON.stringify(MyDerived2.myStatic()) + "<br/>";

TypeScript 结果：

MyDerived.myStatic: []
MyDerived2.myStatic: ["one","two","three"]

ECMA 脚本 6 代码：ES6 Fiddle

class MyBase {
  static myStatic() { return []; }
}

class MyDerived extends MyBase {}

MyBase.myStatic = () => { return ['one', 'two', 'three']; };

class MyDerived2 extends MyBase {}

console.log("MyDerived.myStatic: " + JSON.stringify(MyDerived.myStatic()));
console.log("MyDerived2.myStatic: " + JSON.stringify(MyDerived2.myStatic()));

ECMA 脚本 6 结果

MyDerived.myStatic: ["one","two","three"]
MyDerived2.myStatic: ["one","two","three"]

【问题讨论】：

标签： static typescript ecmascript-6

【解决方案1】：

我观察到的行为是 TypeScript 的预期行为吗？我观察到的行为是 ECMA 脚本 6 的预期行为吗？

是的，是的。类允许运行时修改并按定义顺序处理。 inherit 仅在定义点起作用，因此取决于 在该点的基础属性。

【讨论】：

【解决方案2】：

See related TypeScript bug report

以下是具有一致行为并遍历继承层次结构的 TypeScript 和 ES6 代码示例：

TypeScript 代码：

class MyBase {
  static myStatic() { return []; }
}

class MyDerived extends MyBase {
  static myStatic() { return ['mickey', 'goofy', super.myStatic()]; }
}

MyBase.myStatic = () => { return ['one', 'two', 'three']; };

class MyDerived2 extends MyBase {
  static myStatic() { return ['mickey', 'goofy', super.myStatic()]; }
}

document.body.innerHTML += ("MyDerived.myStatic: " + JSON.stringify(MyDerived.myStatic()) + "<br/>");
document.body.innerHTML += ("MyDerived2.myStatic: " + JSON.stringify(MyDerived2.myStatic()) + "<br/>");

TypeScript 结果：

MyDerived.myStatic: ["mickey","goofy",["one","two","three"]]
MyDerived2.myStatic: ["mickey","goofy",["one","two","three"]]

ES6 代码：ES6 Fiddle

class MyBase {
  static myStatic() { return []; }
}

class MyDerived extends MyBase {
  static myStatic() { return ['mickey', 'goofy', super.myStatic()]; }
}

MyBase.myStatic = () => { return ['one', 'two', 'three']; };

class MyDerived2 extends MyBase {
  static myStatic() { return ['mickey', 'goofy', super.myStatic()]; }
}

console.log("MyDerived.myStatic: " + JSON.stringify(MyDerived.myStatic()));
console.log("MyDerived2.myStatic: " + JSON.stringify(MyDerived2.myStatic()));

ES6 结果

MyDerived.myStatic: ["mickey","goofy",["one","two","three"]]
MyDerived2.myStatic: ["mickey","goofy",["one","two","three"]]

【讨论】：