如何确定一个类中的泛型类型? [英] How to determine the type of generic in a class?

问题描述

如果我有诸如此类的课程

If I have a class such as

class Foo<T>{}

如何检查方法中类的实例的类型?意思是类似

How do I check what type the instance of the class is in the method? Meaning, something like

public barbaz(){
  // Does not work
  if(typeof(<T>) === 'number'){}
}

推荐答案

此处是解决方法.看下一个例子:

THere is workaround here. Take a look on next example:

interface HandleNumbers {
  add(arg: number): number
}

interface HandleStrings {
  concat(a: string, b: string): string;
}

class Api {
  add = (arg: number) => arg + 1
  concat = (a: string, b: string) => a.concat(b)
}

interface HandleHttp {
  <T extends void>(): {};
  <T extends string>(): HandleStrings;
  <T extends number>(): HandleNumbers;
}

const handleHttp: HandleHttp = <_ extends string | number>() => new Api();

handleHttp<number>() // you can only call [add] method
handleHttp<string>() // you can only call [concat] method
handleHttp() // unable to call any method

请记住，您生成的JS代码将包含方法 add 和 concat .

Please keep in mind, your generated JS code will contain both methods add and concat.

因此，在某种程度上，您调用方法的能力取决于所提供的泛型

So, in some way, your ability to call methods depends on provided generic

您可以在此处

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