角钢2.管道.无法读取未定义的属性 [英] angular 2. Pipes. Cannot read property of undefined

问题描述

我制造了烟斗

@Pipe({
  name: 'orgFilter'
})
export class OrgFilterPipe implements PipeTransform {
    transform(orgs: Organization[], args: String[]): any {
        console.log(orgs)
       let filter = args[0].toLowerCase();
       return filter ? orgs.filter((org:Organization) => org.name.toLowerCase().indexOf(filter) != -1): orgs;
}

并在html中使用它:

and using it in html:

<tbody>
        <tr *ngFor="#organization of organizations | orgFilter:listFilter.value">
            <td>{{ organization.organizationName }}</td>
            <td>{{ organization.city }}</td>
            <td>{{ organization.state }}</td>
            <td>{{ organization.country }}</td>
            <td>
                <i class="material-icons">mode_edit</i>
            </td>
            <td>
                <i class="material-icons">delete</i>
            </td>
        </tr>
        <tr>
            <td>
                <div class="col-md-4"><input type="text" #listFilter (keyup)="0" /></div>
            </td>
            <td></td>
            <td></td>
            <td></td>
            <td></td>
            <td></td>
        </tr>
</tbody>

我遇到错误 browser_adapter.js:84 TypeError:无法读取未定义的属性"toLowerCase" 在t.transform(orgFilter.ts:9)

i am getting an error browser_adapter.js:84 TypeError: Cannot read property 'toLowerCase' of undefined at t.transform (orgFilter.ts:9)

问题出在let filter = args [0] .toLowerCase();.

the problem lies in let filter = args[0].toLowerCase();

是什么原因造成的?这是否意味着args没有任何值?我应该在某处声明它吗?我在html中使用管道错误吗? 如果我删除管道，则会看到带有数据的表格.但是当我将其放入html中时，数据消失了，表中只有此输入字段

what is causing it? does this mean that args doesn't have any values? should i declare it somewhere? am i using pipe wrong in html? if i remove the pipe i see table with data. but when i put it into html the data disappears and there is only this input field in the table

推荐答案

鉴于您提供的模板，看来Organization的实例没有名为"name"的成员，而是名为"organizationName"的成员.

Given the template you provided, it looks like instances of Organization have no member called "name", but a member called "organizationName" instead.

也许您可以尝试替换

org.name.toLowerCase().indexOf(filter) != -1

使用

org.organizationName.toLowerCase().indexOf(filter) != -1

在您的代码中.

更新

也就是说，您可以尝试使用其他方法来绑定表达式:

That said, you can try a different way of binding you filter expression:

@Pipe({
  name: 'orgFilter'
})
export class OrgFilterPipe implements PipeTransform {
    transform(orgs: Organization[], expression:string): any {
       if(!expression){
            return orgs;
       }
       else {
            return orgs.filter((org:Organization) => org.organizationName.toLowerCase().indexOf(expression) != -1)
       }
} 

其中表达式是指组件的成员，例如:

Where expression refers to a member of your component, let's say:

filterExpression: string;

然后将输入文本更改为:

Then change your input text to:

<input type="text" [(ngModel)]="filterExpression">

并将管道调用更改为:

<tr *ngFor="#organization of organizations | orgFilter:filterExpression">

根据文档对于列表过滤器，您可能需要使用以下命令声明您的管道不纯:

According to the documentation for a list filter you may have to declare your pipe as impure using:

@Pipe({
  name: 'orgFilter',
  pure: false

})

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