打字稿中的泛型是什么?

问题描述：

我对Typescript完全陌生，以前从未接触过C#或Java. 因此，即使我在官方打字稿网站上阅读了说明，我也真的不理解Generics的真正用法.

I am totally new to typescript and never into c# or java before. So even if I read the instruction on official typescript website, I really do not understand the real use of Generics.

这是Generics的简单示例.下面执行此操作的真正好处是什么?

Here is the simple example of Generics. What is the real benefits of doing this below?

function identity<T>(arg: T): T {
    return arg;
}

var output = identity<string>("myString");

没有泛型，我可以在下面这样做(或者我可以使用Interfaces确保传递指定的参数.)

without Generics, I can just do this way below (or I can use Interfaces to make sure to pass specified arguments.)

function identity(arg: any): any  {
    return arg;
}
var output = identity("myString");

任何建议将不胜感激. 谢谢

Any advice would be appreciated. Thank you

答

仅从您的基本示例开始:

Just going from your basic example:

function identity<T>(arg: T): T {
    return arg;
}

在此处具有通用会在自变量(arg:T)和返回类型: T{之间强制执行约束.这使编译器可以从参数推断出返回类型，如下所示:

Having a generic here enforces a constraint between the argument (arg:T) and the return type : T{. This allows the compiler to infer the return type from the argument as shown below:

function identity<T>(arg: T): T {
    return arg;
}

let str = identity('foo');
// str is of type `string` because `foo` was a string

str = '123'; // Okay;
str = 123; // Error : Cannot assign number to string

打字稿中的泛型是什么?

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