搜索词

mixin,构造函数参数

建议

允许mixin构造函数在剩余参数之前有参数，并推断mixin参数之间的组合。

用例

以下js代码是完全有效的且功能性的。然而，由于实际的mixin构造函数约束，我们无法在Typescript中重现此代码。

const mixin1 = (base) => class Mixin1 extends base {
    constructor(m1v1, m1v2, ...args) {
        super(...args);
        this.m1v1 = m1v1;
        this.m1v2 = m1v2;
    }
};
const mixin2 = (base) => class Mixin2 extends base {
    constructor(m2v1, m2v2, ...args) {
        super(...args);
        this.m2v1 = m2v1;
        this.m2v2 = m2v2;
    }
};
class Base {
    constructor(v1, v2) {
        this.v1 = v1;
        this.v2 = v2;
    }
}
class C1 extends mixin1(Base) {
}
class C2 extends mixin2(Base) {
}
class C3 extends mixin2(mixin1(Base)) {
}
console.log(new C1("m1v1", true, 1, {}));
console.log(new C2(false, 2, 1, {}));
console.log(new C3(false, 2, "m1v1", true, 1, {}));

示例

在ts中使用构造函数推断，相同的代码应该可以正常工作。

type Constructor = new (...args: any[]) => object;

const mixin1 = <T extends Constructor>(base: T) =>
    class Mixin1 extends base {
        m1v1: string;
        m1v2: boolean;

        constructor(m1v1: string, m1v2: boolean, ...args: any[]) {
            super(...args);

            this.m1v1 = m1v1;
            this.m1v2 = m1v2;
        }
    }

const mixin2 = <T extends Constructor>(base: T) =>
    class Mixin2 extends base {
        m2v1: boolean;
        m2v2: number;

        constructor(m2v1: boolean, m2v2: number, ...args: any[]) {
            super(...args);

            this.m2v1 = m2v1;
            this.m2v2 = m2v2;
        }
    }

class Base {
    v1: number;
    v2: object;

    constructor(v1: number, v2: object) {
        this.v1 = v1;
        this.v2 = v2;
    }
}

class C1 extends mixin1(Base) {
}

class C2 extends mixin2(Base) {
}

class C3 extends mixin2(mixin1(Base)) {
}

console.log(new C1("m1v1", true, 1, { })); // infer mixin1 and Base parameters: [string, boolean, number, object]
console.log(new C2(false, 2, 1, { })); // infer mixin2 and Base parameters: [boolean, number, number, object]
console.log(new C3(false, 2, "m1v1", true, 1, { })); // infer mixin2, mixin1 and Base parameters: [boolean, number, string, boolean, number, object]

检查清单

我的建议满足以下准则：

• 这不会对现有的TypeScript/JavaScript代码造成破坏性更改
• 这不会改变现有JavaScript代码的运行时行为
• 这可以在不根据表达式的类型发出不同的JS的情况下实现
• 这不是一个运行时特性(例如库功能，带有JavaScript输出的非ECMAScript语法等)
• 这个特性将与TypeScript's Design Goals的其他部分保持一致。