Angular ViewChild fileInput註解未定義

Question

如果我的fileInput元素是在一個正常的div，那麼它工作正常。但是，如果我把它放在<ng-template></ng-template>內，那麼我就會得到undefined。

這裏是我的代碼：

HTML

<ng-template #content let-c="close" let-d="dismiss"> 
    <div class="modal-header"> 
     <h4 class="modal-title">Modal title</h4> 
     <button type="button" class="close" aria-label="Close" (click)="d('Cross click')"></button> 
    </div> 
    <div class="modal-body"> 
     <form #documentsForm="ngForm" (ngSubmit)="onEditSubscriberDocumentsSubmit(documentsForm.value);documentsForm.reset()"> 
     <input #fileInput type="file" #select name="document" [(ngModel)]="document" (click)="onDocUpload()" />  
     <input type="submit" value="Save" class="btn btn-success" [hidden]="addDocHidden"> 
     </form> 
    </div> 
    <div class="modal-footer"> 
     <button type="button" class="btn btn-outline-dark" (click)="c('Close click')">Close</button> 
    </div> 
</ng-template> 

TS

import { Component, OnInit, ViewChild , ElementRef} from '@angular/core';

export class EditSubscriberComponent { 
    constructor(private http: Http, private route: ActivatedRoute, private router: Router, private modalService: NgbModal) { } 
    @ViewChild("fileInput") fileInput: ElementRef; 
    ngOnInit() { 
     console.log(this.fileInput) 
     // This is undefined. If I place the <input #fileInput type="file"> 
     // in the main div,not under ng-template, then I am getting the 
     // desired output 
    } 
} 

請建議我該怎麼交流從納克模板塞斯ViewChild

Answer 1

您可以使用setter方法：

@ViewChild("fileInput") 
set fileInput(val: ElementRef) { 
    if(val) { 
    console.log(val); 
    } 
} 

或訂閱上@ViewChildren變化：

@ViewChildren("fileInput") fileInputs: QueryList<ElementRef>; 

ngAfterViewInit() { 
    this.fileInputs.changes.subscribe(x => { 
    if(x.length) { 
     console.log(x[0]); 
    } 
    }) 
} 

，或者如果你確切地知道你的模板被初始化就用@ViewChild

@ViewChild("fileInput") fileInput: ElementRef; 

... 
this.vcRef.createEmbeddedView(this.template); // pseudo code 
console.log(this.fileInput);