[英]Get the type of generic function without invoking the function in typescript
我有一個像這樣的通用函數:
function foo<T>(val: T) { return val; }
我有一些類型:
type StringType = string;
type NumType = number;
現在,我想引用給定類型的'foo'函數,但是它不起作用:
const stringFunc = foo<StringType>;
const numFunc = foo<NumType>;
請注意,我不想調用'foo'函數,否則,我可以這樣做:
const stringFunc = (val: string) => foo<StringType>(val);
const numFunc = (val: number) => foo<NumType>(val);
可能嗎?
如果您只想強制鍵入而又不介意額外鍵入,則可以這樣操作:
const stringFunc: (val: string) => string = foo;
const numFunc: (val: number) => number = foo;
但目前尚無法將類型參數應用於通用函數。
如何進行類型轉換或調用其他一些自組織通用函數?
function foo<T>(v: T) { return v }
type UnaryFunction<T> = (v: T) => T
// casting
const asStrFoo = foo as UnaryFunction<string> // asStrFoo(v: string): string
const asNumFoo = foo as UnaryFunction<number> // asNumFoo(v: number): number
// identity function
const bind = <T>(f: UnaryFunction<any>): UnaryFunction<T> => f
const strFoo = bind<string>(foo) // strFoo(v: string): string
const numFoo = bind<number>(foo) // numFoo(v: number): number
// function factory
function hoo<T>() { return function foo(v: T) { return v } }
// function hoo<T>() { return (v: T) => v }
const strHoo = hoo<string>() // strHoo(v: string): string
const numHoo = hoo<number>() // numHoo(v: number): number
注意
// This condition will always return 'false' since the types 'UnaryFunction<string>' and 'UnaryFunction<number>' have no overlap.
console.log(strFoo === numFoo) // true
// This condition will always return 'false' since the types 'UnaryFunction<string>' and 'UnaryFunction<number>' have no overlap.
console.log(asStrFoo === asNumFoo) // true
// This condition will always return 'false' since the types '(v: string) => string' and '(v: number) => number' have no overlap.
console.log(strHoo === numHoo) // false
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