[英]how to achieve overload in typescript
I konw there is a way in typescript like this:我知道 typescript 中有这样的方法:
function foo(arg: number): string;
function foo(arg: string): number;
function foo(): any {
if (typeof arguments[0] === "string") {
return +arguments[0];
} else {
return arguments[0].toString();
}
}
foo(1) // '1'
foo("hello") // NaN
foo("2") // 2
But when I have same number of parameters and each parameter is custom type, like this但是当我有相同数量的参数并且每个参数都是自定义类型时,就像这样
interface Dog {
run: number;
}
interface Bird {
fly: number;
}
function foo(arg: Dog): number;
function foo(arg: Bird): number;
function foo(): any {
}
How can I tell the difference between these parameters我如何分辨这些参数之间的区别
TypeScript is JavaScript, so you basically have to do the same thing. TypeScript 是 JavaScript,所以你基本上必须做同样的事情。 In order to make your compiler happy, you can implement type guards.
为了让你的编译器满意,你可以实现类型保护。
https://www.typescriptlang.org/docs/handbook/advanced-types.html#user-defined-type-guards https://www.typescriptlang.org/docs/handbook/advanced-types.html#user-defined-type-guards
function isDog(pet: Dog | Bird): pet is Dog {
return 'run' in pet
}
You can use these in your code to tell TypeScript that you've validated the type for runtime.您可以在代码中使用这些来告诉 TypeScript 您已经验证了运行时的类型。
function foo(arg?: Dog | Bird): void | number {
if(arg) {
if(isDog(arg)) {
return arg.run;
} else {
return arg.fly;
}
}
}
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