Typescript

Question

我想使用 Knockout observables 将普通的旧 Javascript 类型映射到等效类型。

interface KnockoutObservableArray<T> { }
interface KnockoutObservable<T> { }

class CustomerDto {
    Name: string;
    PetLicenseNumbers: number[];
}

// manually mapped to Knockout-equivalent 
class CustomerDtoKo {
    Name: KnockoutObservable<string>;
    PetLicenseNumbers: KnockoutObservableArray<number>;
}

我正在尝试使用映射类型来自动执行上述操作，但我做不到找到一种有条件地将数组映射到 KnockoutObservableArray<U> 的正确方法将标量映射到 KnockoutObservable<U>

type KnockoutType<T> = {
    //[K in keyof T] : KnockoutObservableArray<T[K][0]>
    [K in keyof T] : KnockoutObservable<T[K]>
}

type CustomerDtoKo2 = KnockoutType<CustomerDto>;
// gives
type CustomerDtoKo2 = {
    Name: KnockoutObservable<string>,
    PetLicenseNumbers: KnockoutObservable<number[]> // should be KnockoutObservableArray<number>
}

Answer 1

如你所料，conditional types会帮助你：

type KnockoutType<T> = {
    [K in keyof T]: T[K] extends Array<infer U> ? 
      KnockoutObservableArray<U> : KnockoutObservable<T[K]>
}

祝你好运！

Typescript - 条件映射类型

Typescript - conditional mapped types

knockout.js