仅用于特定属性类型的属性装饰器 [英] Property decorator only for a specific property type

问题描述

我在TypeScript中有一个属性装饰器，该装饰器仅可用于 Array 类型的属性。要强制执行此操作，如果属性类型不是 Array （使用，则在运行时会引发 TypeError https://github.com/Microsoft/TypeScript-Handbook/blob/master/pages/Decorators.md#metadata rel = nofollow noreferrer>反射元数据以获取属性类型信息）：

I have a property decorator in TypeScript that is only usable on properties of type Array. To enforce this, a TypeError is thrown at runtime if the property type is not Array (using reflect metadata to get property type information):

function ArrayLog(target: any, propertyKey: string) {
    if (Reflect.getMetadata("design:type", target, propertyKey) !== Array) {
        throw new TypeError();
    }

    // ...
}

但是，我认为这对开发人员不太友好。我如何才能使TypeScript编译器允许在具有特定类型的属性上仅使用特定的属性装饰器 ？

However, I wouldn't consider this too dev-friendly. How could I make it so that the TypeScript compiler allows using a certain property decorator only on properties with a certain type?

推荐答案

有一个技巧可以实现此目的：

There is a little trick to achieve this:

function ArrayLog<K extends string, C extends { [ A in K ]: Array<any> }>(target: C, key: K) {
    /* ... */
}

甚至更好（请参见 https://stackoverflow.com/a/47425850/274473）：

function ArrayLog<K extends string, C extends Record<K, Array<any>>>(target: C, key: K) {
    /* ... */
}

不幸的是，这仅适用于公共财产，不适用于私人或受保护财产...

Unfortunately this only works for public properties, not for private or protected properties...

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