[英]Defining return type of Factory method with TypeScript generics
Essentially I want to be able to call a generic TypeScript function with a constructor function and return a correctly typed variable of the type of the product of the constructor function. 本质上,我希望能够使用构造函数来调用通用TypeScript函数,并返回构造函数的乘积类型正确类型的变量。 See code example below.
请参见下面的代码示例。 Final console.log has type errors.
最终console.log具有类型错误。
class TestType {
constructor(
public someVal: number
) {}
}
type GenericConstructor = new (...args: any) => any;
let map = new Map<GenericConstructor, any>();
map.set(TestType, new TestType(7));
console.log(map.get(TestType).someVal);
function retrieve<T extends GenericConstructor>(constructor: T): T {
return map.get(constructor);
}
let retrieved = retrieve(TestType);
console.log(`retrieved: ${retrieved.someVal}`);
I've searched other answers and nothing seems to quite cover this. 我搜索了其他答案,似乎没有什么能掩盖这一点。 I also feel like this might be impossible as I'm trying to extract the type generically and not from an instance.
我也觉得这可能是不可能的,因为我试图从类型而不是从实例中提取类型。
At simplest I want this function to work, with correct typing: 最简单地说,我希望此功能可以正确键入以下内容:
let val: SomeType = retrieve(SomeTypeConstructor);
Is this possible, without a second type parameter? 没有第二种类型的参数,这可能吗?
InstanceType<T>
is what you need: InstanceType<T>
是您需要的:
function retrieve<T extends GenericConstructor>(constructor: T): InstanceType<T> {
return map.get(constructor);
}
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