Question

<mat-select [(ngModel)]='selected' >
   <mat-option *ngFor="let language of languages" [value]="language" >
      {{language}}
   </mat-option >
</mat-select>

这是我的html

selected:string
constructor(private firestore: AngularFirestore,private globals:GlobalsService) { 
  console.log(this.globals.userUid);
  this.firestore.collection('customers').doc(this.globals.userUid).get().subscribe(function(doc){
    if(doc.exists){
      console.log(doc.data()["language"]);
      this.selected  = doc.data()["language"]
    }
  })
  for (let index = 0; index < avaibleLanguages.length; index++) {
    const language:string = avaibleLanguages[index]
    this.languages.push(language)
  }}

在console.log中，我看到我从firebase收到了正确的语言，但是没有将其设置为默认选择。这里所有其他东西都起作用

Answer 1

只需要将值放在局部变量中即可。

var local
    this.firestore.collection('customers').doc(this.globals.userUid).get()
    .subscribe(doc =>{
      if(doc.exists){
        local = doc.data()["language"]
      }
    },err => console.log(err),()=>{this.selected = local }
    )
    for (let index = 0; index < avaibleLanguages.length; index++) {
      const language:string = avaibleLanguages[index]
      this.languages.push(language)
    }

Answer 2

如果症状持续，请使用ChangrDetectorRef：在此处https://angular.io/api/core/ChangeDetectorRef

...
constructor (private changeDetector: ChangeDetectorRef) { }

private someFn(): void {
    this.changeDetector.detach();
    this.changeDetector.reattach();
    this.changeDetector.detectChanges();
}
...

如何设置垫选的默认值？

2 个答案: