你如何运行NgFor在Angular2结果的功能？ [英] How do you run a function on the result of NgFor in Angular2?

问题描述

考虑系统中所有用户的列表：

Consider a list of all of the users in your system:

  allUsers = {
    a: {name:'Adam',email:'[e-mail]',level:'admin',group:'Owners'},
    b: {name:'Barbra',email:'[e-mail]',level:'admin',group:'Owners'},
    c: {name:'Chris',email:'[e-mail]',level:'standard',group:'Managers'},
    d: {name:'Dennis',email:'[e-mail]',level:'standard',group:'Managers'},
    e: {name:'Elizabeth',email:'[e-mail]',level:'standard',group:'Staff'},
    f: {name:'fred',email:'[e-mail]',level:'visitor',group:'Visitor'},

  }

然后，用户在一个项目的列表：

Then a list of the users on a project:

usersList = ['a','b','d','f'];

所以，你有一个很好的功能，方便取的用户ID和查找的用户详细信息的其余部分：

So you have a nice easy function to take the user id and lookup the rest of the user details:

  getUser(userId){
    console.log('Getting User with Id:', userId);
    if(allUsers[userId]) return allUsers[userId];
  }

然后在模板中使用* ngFor遍历在列表中的用户，但你要那么查找的全套细节

Then in the template you use *ngFor to loop through the users in the list, but you want to then lookup the full set of details

<tr *ngFor="#userId in usersList" #user="getUser(userId)">
  <td>{{user.name}}</td>
</tr>

没有工作...
如果没有创建自定义组件或其它更复杂的东西，我无法弄清楚如何每个用户运行一次的getUser功能。我当然可以一遍又一遍地像运行：

Doesn't work... Without creating custom components or other more complex stuff I can't figure out how to run the getUser function once per user. I can of course run it over and over like:

<td>{{getUser(userId).name}}</td>

但这似乎并不像最好的办法。
是否有更简单的方式来获得访问用户id变量，并将其设置为一个局部变量？

but this doesn't seem like the best way. Is there an easier way to get access to the userId variable and set it as a local variable?

这里是我一直在玩什么迄今一个plunker

Here's a plunker of what I've been playing with so far

推荐答案

虽然你可以创建ngFor模板指令的变量，但该变量只能取指数，偶，奇和放值;持续。

Though you can create a variable on ngFor template directive, but that variable can only take value of index, even, odd & last.

这就是为什么我会用管这种情况下，你需要通过 usersList ＆安培; ALLUSERS 自定义 @Pipe getUsers（它将起到相同Angular1过滤器）。

Thats why I could use pipe for this case, where you need to pass usersList & allUsers to custom @Pipe getUsers (it will act same as a filter in Angular1).

标记

<tr *ngFor="#user of usersList | getUsers: allUsers">
  <td>
    {{user.name}}
  </td>
  <td>
    {{user.email}}
  </td>
  <td>
    {{user.level}}
  </td>
  <td>
    {{user.group}}
  </td>
</tr>

code

@Pipe({
  name: 'getUsers',
  pure: false
})
export class GetUserPipe implements PipeTransform {
  constructor(){
    this.test = 'Test';
  }
  transform(array:Array<string>, object: any) : any {
    // for..in loop
    let output = [];
    for (var num in array)
    {
      // somehow object goes inner side
      output.push(object[0][array[num]]);
    }
    console.log(output)
    return output;
  }
}

演示Plunkr

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