有接口扩展字符串功能

问题描述

我一起使用这些工具：

• TypeScript


• Gulp


• Gulp-Inject

我试图执行以下操作：

  module My {
 interface IGulpInjectable extends string {//<<问题在这里！ 
 [gulp_inject：string]：string; 
} 
 
 export class Cache {
 private items：{[key：string]：IGulpInjectable}; 
 $ b构造函数（）{
 this.items = {
item1：{gulp_inject：file1.html}，
item2：{gulp_inject： file2.html} 
} 
} 
 
 getItem（key：string）{
 return this.items [key] .trim（）; 
 
 
 
  

gulp-inject 是用包含文件内容的字符串替换 {gulp_inject：x.html} 。这就是为什么我想要 IGulpInjectable 扩展字符串：这样像 trim（） 将被TypeScript理解。

但是，扩展字符串无效。 都不扩展字符串。至少，不是用我目前的构造函数代码，我不希望改变它。

如何告诉TypeScript我的界面的所有方法都是字符串有？

---

脚注，我当前的解决方法：

  getItem（key：string）{
 return（< any> this.items [key]）。trim（）; 
} 
  

但这并不令人满意。

  interface IGulpInjectable 
 
扩展字符串
 {
 gulp_inject：string; 
} 
 
 class Cache 
 {
 private items：{[key：string]：IGulpInjectable}; 
 
 
构造函数（）
 {
 
 let item1 = new String（123）; 
 item1 [gulp_inject] =file1.html; 
 
 let item2 = new String（4556）; 
 item2 [gulp_inject] =file2.html; 
 $ b $ this.items = {
item1：< IGulpInjectable> item1，
item2：< IGulpInjectable> item2 
} 
} 
 
 getItem（key：string）
 {
 return this.items [key]; 
} 
} 
 
让c = new Cache（）; 
 let i = c.getItem（item1）; 
 console.log（i.trim（））; //输出'123'
 console.log（i.gulp_inject）; //输出'file1.html'
  

链接：

希望这会有所帮助。

I'm using these tools together:

• TypeScript
• Gulp
• Gulp-Inject

I'm trying to do the following:

module My {
    interface IGulpInjectable extends string { // << Problem here!
        [gulp_inject: string] : string;
    }

    export class Cache {
        private items: { [key: string] : IGulpInjectable };

        constructor() {
            this.items = {
                "item1": { gulp_inject: "file1.html" },
                "item2": { gulp_inject: "file2.html" }
            }
        }

        getItem(key: string){
            return this.items[key].trim();
        }
    }
}

What gulp-inject does is replace { gulp_inject: "x.html" } with a string containing the file contents. This is why I want to have IGulpInjectable extend string: so that methods like trim() will be understood by TypeScript.

However, extends string is not valid. Neither is extends String. At least, not with my current constructor code, which I prefer not to change.

How can I tell TypeScript that my interface has all methods a string has?

---

Footnote, my current workaround:

        getItem(key: string){
            return (<any> this.items[key]).trim();
        }

But that's not quite satisfying.

解决方案

The following code works fine in typescript playground:

interface IGulpInjectable extends String 
{ 
    gulp_inject: string;
}

class Cache 
{
    private items: { [key: string] : IGulpInjectable };


    constructor() 
    {

        let item1 = new String("   123   ");
        item1["gulp_inject"] = "file1.html";

        let item2 = new String("   4556  ");
        item2["gulp_inject"] = "file2.html";

        this.items = {
            "item1": <IGulpInjectable>item1,
            "item2": <IGulpInjectable>item2
        }
    }

    getItem(key: string)
    {
        return this.items[key];
    }
}

let c = new Cache();
let i = c.getItem("item1");
console.log(i.trim()); //output '123'
console.log(i.gulp_inject); //output 'file1.html'

Link: typescript playground

Hope this helps.

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