Question

你好吗？我有一个问题＆＃39;切片＆＃39;在我的项目中未定义。我使用自动填充材料https://material.angular.io/components/autocomplete/examples

我的代码 //从webservice获取所有国家/地区

this.ws.AllCountry().subscribe(
      countryes => {
        this.countryes = countryes.map((country) => {
          return new Country(country);
        });
      }
    );

//创建FilterOptions

   this.stateCtrl = new FormControl();
    this.filteredOptionsCountry = this.stateCtrl.valueChanges
      .pipe(
      startWith(''),
      map(country =>  country ? this.filterCountry(country) : this.countryes.slice()) // Cannot read property 'slice' of undefined
    );

//过滤国家/地区

 filterCountry(name: string) {
    return this.countryes.filter(country =>
      country.name.toLowerCase().indexOf(name.toLowerCase()) === 0);
  }

Code.html

 <form class="example-form">
     <mat-form-field class="example-full-width">
     <input matInput placeholder="Select Country" aria-label="State" [matAutocomplete]="auto" [formControl]="stateCtrl">
       <mat-autocomplete #auto="matAutocomplete">
         <mat-option *ngFor="let country of filteredOptionsCountry | async" [value]="country.country_id">
           {{ country.name }}
         </mat-option>
       </mat-autocomplete>
     </mat-form-field>
   </form>

你能告诉我一些想法，问题是什么？

谢谢

Answer 1

我认为你在订阅内部之前使用的是乡村人，我建议在allCountry订阅中移动你的“Create FilterOptions”代码，其中定义了countryes

Answer 2

尝试一下...

map（（country：string | null）=> country？this._filter（country）：this.countryes.slice（）））;

ERROR TypeError：无法读取属性＆＃39; slice＆＃39; undefined --- Typescript

2 个答案: