angular 2数组的名称为“ undefined”

Question

Here is the situation.

I am trying to get a number from my database but every time I put the number into the Array(), it says undefined.

I am able to get the number as I can display it in my HTML but inside the array, does not work.

any idea why this is happening?

 import { Component, OnInit } from '@angular/core'; import { DomSanitizer, SafeResourceUrl, SafeUrl, SafeHtml } from '@angular/platform-browser'; import { ActivatedRoute } from '@angular/router'; import { RealEstatePhotography } from '../real-estate-photography'; import { RealEstatePhotographyService } from '../real-estate-photography.service'; @Component({ selector: 'app-real-estate-photography-detail', templateUrl: './real-estate-photography-detail.component.html', styleUrls: ['./real-estate-photography-detail.component.css'], providers: [RealEstatePhotographyService], }) export class RealEstatePhotographyDetailComponent implements OnInit { realEstate; amount photos = Array(this.amount) constructor(private route: ActivatedRoute, private _realEstatePhotographyService: RealEstatePhotographyService, private sanitizer: DomSanitizer) {} ngOnInit(){ this.route.params.subscribe(params => { let title = params['title']; let realEstate = this._realEstatePhotographyService.getItem(title).subscribe(realEstate => { this.realEstate = realEstate; this.amount = this.realEstate.amount }); }); } } 

Answer 1

Amount is not defined at that time. You need to update photos every time.

export class RealEstatePhotographyDetailComponent implements OnInit {


realEstate;
amount: Number;
photos: Photo[] = [];

  constructor(private route: ActivatedRoute, private _realEstatePhotographyService: RealEstatePhotographyService, private sanitizer: DomSanitizer) {}


  ngOnInit(){
    this.route.params.subscribe(params => {
      let title = params['title'];
      let realEstate = this._realEstatePhotographyService.getItem(title).subscribe(realEstate => {
        this.realEstate = realEstate;
        this.amount = this.realEstate.amount;
        this.photos.push(realEstate.photo);
      });

    });
}

EDIT:

Just realized that you're probably trying to define the size of the array -- there's no need to do that in javascript. Just declare it as an empty array and push in your photos as needed.