枚举作为 TypeScript 中的参数 [英] Enum as Parameter in TypeScript

问题描述

不能将参数的类型设置为枚举吗?像这样:

private getRandomElementOfEnum(e : enum):string{var length:number = Object.keys(e).length;返回 e[Math.floor((Math.random() * length)+1)];}

编译抛出以下错误:

<块引用>

需要参数表达式.(1135)

使用 any 显然一切正常:

private getRandomElementOfEnum(e : any):string{var length:number = Object.keys(e).length;返回 e[Math.floor((Math.random() * length)+1)];}

此代码工作正常.但没有那么优雅和代码约定.

是否有可能或一些解决方法将枚举定义为参数?

解决方案

无法确保参数是枚举，因为 TS 中的枚举不从共同的祖先或接口继承.

TypeScript 带来静态分析.您的代码使用带有 Object.keys 和 e[dynamicKey] 的动态编程.对于动态代码，any 类型很方便.

您的代码有问题:length() 不存在，e[Math.floor((Math.random() * length)+1)] 返回字符串或整数，枚举值可以手动设置...

这是一个建议:

function getRandomElementOfEnum(e: any): E {var 键 = Object.keys(e),index = Math.floor(Math.random() * keys.length),k = 键[索引];if (typeof e[k] === '数字')返回<any>e[k];返回 <any>parseInt(k, 10);}功能显示(a:颜色){控制台日志(一)；}枚举颜色{蓝色，绿色}；显示(getRandomElementOfEnum<颜色>(颜色))；

理想情况下，参数类型 any 应替换为 typeof E 但编译器 (TS 1.5) 无法理解此语法.

Isn't it possible to set the type of a parameter to an Enum? Like this:

private getRandomElementOfEnum(e : enum):string{
    var length:number = Object.keys(e).length;
    return e[Math.floor((Math.random() * length)+1)];
}

Following error is thrown by compilation:

Argument expression expected.(1135)

With any obviously everyhting is alright:

private getRandomElementOfEnum(e : any):string{
    var length:number = Object.keys(e).length;
    return e[Math.floor((Math.random() * length)+1)];
}

This Code works fine. but isn't as elegant and code-convential.

Is there a possibility or a little workaround to define an enum as a parameter?

解决方案

It's not possible to ensure the parameter is an enum, because enumerations in TS don't inherit from a common ancestor or interface.

TypeScript brings static analysis. Your code uses dynamic programming with Object.keys and e[dynamicKey]. For dynamic codes, the type any is convenient.

Your code is buggy: length() doesn't exists, e[Math.floor((Math.random() * length)+1)] returns a string or an integer, and the enumeration values can be manually set…

Here is a suggestion:

function getRandomElementOfEnum<E>(e: any): E {
    var keys = Object.keys(e),
        index = Math.floor(Math.random() * keys.length),
        k = keys[index];
    if (typeof e[k] === 'number')
        return <any>e[k];
    return <any>parseInt(k, 10);
}

function display(a: Color) {
    console.log(a);
}

enum Color { Blue, Green };
display(getRandomElementOfEnum<Color>(Color));

Ideally, the parameter type any should be replaced by typeof E but the compiler (TS 1.5) can't understand this syntax.

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