"EXCEPTION:嵌套组件中"组件视图"上的意外指令值'undefined'

Question

我有两个AngularJS 2.0组件:

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;
}

评论:

import {Component, Injectable, View, 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,可以打印多个Comment组件.在Comment的模板中,我有一个Angular ngIf,如果var commentable为true,则打印一个Comments组件.当我运行它时,我得到:

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

Answer 1

有一种方法可以解决循环依赖问题.

import {forwardRef} from 'angular2/core';
import {Comment} from './Comment.component';

...
directives: [forwardRef(() => Comment)]
})

我试过这个,2.0.0-beta.10它工作正常.有关更多信息,请参阅本期 github上的问题报告中的tlancina发表的评论.

Answer 2

循环TypeScript导入依赖项可能导致此问题.(我刚碰到这个)

为了我:

1. A是父组件,imports和exports B,C,D.为了方便.

2. A尝试渲染B

3. 乙进口Ç 从 一个,并试图呈现Ç.

一旦我将C添加到B的directives块中,我就会得到该错误(无论是否在B的模板中.)实际上,因为A依赖于B,所以我将A中的任何内容导入B的块I得到

意外的指令值'undefined'

@Eirc Martinez是对的,你必须找到解决循环依赖的方法.

Answer 3

当我导入一些不存在的东西时,我经常会遇到这个错误.通常这意味着我的导入中存在拼写错误或具有相同性质的东西.

例如,当我尝试导入时出现此错误:

import {Comment} from './Comment.component';

当我的意思是:

import {CommentComponent} from './Comment.component';