评论：

import {Component,Injectable,View,Input} from 'angular2/core';
import {Comments} from './comments.component';

@Injectable()

@Component({
    selector: 'comment'
})

@View({
    templateUrl: 'res/templates/components/comment.component.html',directives: [Comments]
})

export class Comment {
    @Input() comment;
    @Input() commentable = false;
}

注释 ：

import {Component,Input} from 'angular2/core';
import {CommentsService} from './../services/comments.service';
import {RouteParams} from 'angular2/router';
import {Comment} from './Comment.component';

@Injectable()

@Component({
    selector: 'comments',providers: [CommentsService]
})

@View({
    templateUrl: 'res/templates/components/comments.component.html',directives: [Comment]
})

export class Comments {
    @Input() ID;
    public comments;
    public commentsService: CommentsService;
    public routeParams: RouteParams;

    constructor (routeParams: RouteParams,commentsService: CommentsService) {
        var self = this;

        self.routeParams = routeParams;
        self.commentsService = commentsService;
    }

    ngOnInit()   {
        var self = this;

        if (self.ID !== undefined)
            self.comments = self.commentsService.comments[self.ID];
        else if (self.routeParams.params['id'] !== undefined)
            self.comments = self.commentsService.comments[self.routeParams.params['id']];
        else
            self.comments = undefined;
    }
}

comment.template：

<div class="post">
    <div class="author-pic"></div>
    <div class="body">
        <h2 class="title">{{comment.author.name}} {{comment.author.surname}}</h2>
        <h3 class="title">{{comment.publication | date:"MM/dd/yy"}}</h3>
        <p>{{comment.body}}</p>
    </div>
    <comments *ngIf="commentable" [ID]="comment.ID"></comments>
</div>

comments.template：

<div *ngIf="comments !== undefined">
    <comment *ngFor="#comment of comments" [comment]="comment" [commentable]="true"></commento>
</div>

在评论模板中，我有一个Angular循环打印多个注释组件。在评论模板中，我有一个Angular ngIf，如果var commentable为true，则打印注释组件。当我运行它我得到：

EXCEPTION: Unexpected directive value 'undefined' on the View of component 'Comment'