Angular2 *ngIf 检查模板中的对象数组长度 [英] Angular2 *ngIf check object array length in template

问题描述

参考https://angular.io/docs/ts/latest/guide/displaying-data.html 和堆栈 如何使用 *ngIf 检查 angular 2 模板中的空对象，但仍然收到未定义的语法错误自身上下文.如果我删除 *ngIf 条件，那么我将在 teamMembers 中获取值，如果我将一些值放入其中以便我可以访问 teamMembers 中的值.

我的 teamMember 对象是 [ ] 数组 我正在尝试检查条件数组的大小是否为空.

尝试:

和

//检查长度大于抛出语法错误<div class="col-md-12"><h4>团队成员</h4><ul class="avatar" *ngFor="let member of teamMembers"><li><a href=""><gravatar-image [size]="80" [email]="member.email"></gravatar-image></a></li>

组件:

@Component({选择器:'pbi-editor',})导出类 AppComponent 实现 OnInit {团队成员:用户[]；

任何帮助都会很棒.

解决方案

这首先检查 teamMembers 是否有值，如果 teamMembers 没有值，它不会尝试访问 lengthundefined 因为条件的第一部分已经失败.

Refered to https://angular.io/docs/ts/latest/guide/displaying-data.html and stack How to check empty object in angular 2 template using *ngIf still getting syntax error self context undefined. If I remove *ngIf condition then I am getting values in teamMembers if I push some value into it so I can access values in teamMembers.

my teamMember object is [ ] array i am trying to check condition array is empty by size.

Tries :

<div class="row" *ngIf="(teamMembers | json) != '{}'">

and

<div class="row" *ngIf="teamMembers.length > 0"> //Check length great than
                                                 throwing syntax error
            <div class="col-md-12">
                <h4>Team Members</h4>
                <ul class="avatar" *ngFor="let member of teamMembers">
                    <li><a href=""><gravatar-image [size]="80" [email]="member.email"></gravatar-image></a></li>
                </ul>
            </div>
        </div>

Component :

@Component({
selector: 'pbi-editor',
})
export class AppComponent implements OnInit {
teamMembers: User[];

Any help would be great.

解决方案

<div class="row" *ngIf="teamMembers?.length > 0">

This checks first if teamMembers has a value and if teamMembers doesn't have a value, it doesn't try to access length of undefined because the first part of the condition already fails.

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