Ionic 2：从popover回调访问主页的服务

I've been on angularJs for a while now and I just switched over to angular 2. I'm calling a popover from a page and when an item is selected from the popover, I'm supposed to get some data from an api. The problem I'm having is, when I use 'this', it no longer references the Vendor context so I'm unable to access the VendorServices functions. Is there a way to reference the parent class(the page calling the popover) so I get all it's variables?

我已经在angularJs上呆了一段时间了,我刚刚切换到了角度2.我正在从一个页面调用一个弹出框,当从弹出框中选择一个项目时,我应该从api获取一些数据。我遇到的问题是,当我使用'this'时,它不再引用Vendor上下文,因此我无法访问VendorServices函数。有没有办法引用父类(调用popover的页面)所以我得到它的所有变量?

import { Component } from '@angular/core';
import { VendorService} from '../vendors/services'
import { NavController, NavParams } from 'ionic-angular';
import { Meals } from '../meals/meals';
import { PopoverController } from 'ionic-angular';
import { LocationsPopover } from '../locations-popover/locations-popover';

@Component({
  selector: 'vendors',
  templateUrl: 'vendors.html'
})
export class Vendors {

  mealsPage = Meals;
  public locationName: string;
  vendors: any;
  selectedLocation:String;


  constructor(public navCtrl: NavController, public params:NavParams, private vendorService:VendorService, public popoverController: PopoverController) {
    this.locationName = params.get('location');

  }

this is the function that handles the popover:

这是处理弹出窗口的函数:

  showLocationsDropdown(event){
    console.log("locations");
    let popover = this.popoverController.create(LocationsPopover,{
      cb:function(location){
        this.selectedLocation = location.location_name;
        console.log("selectedLocation", location.location_name);
        // this.vendorService.getVendorsByLocationId(location.id).subscribe(
        this.vendorService.getVendors().subscribe(
          results=>{
            console.log(results);
            this.vendors = results;
          }
        );
      }
    });
    popover.present({
      ev:event
    });
  }

This is the error I get

这是我得到的错误

1 个解决方案

#1

If you use function(location){ like that then the enclosing scope of the this inside the function will be the functions "instance". You can do something like (location)=>{ to access the lexical this

如果使用函数(位置){那样那么函数内部的封闭范围将是函数“instance”。你可以做一些像(location)=> {来访问这个词汇

showLocationsDropdown(event){
        console.log("locations");
        let popover = this.popoverController.create(LocationsPopover,{
          cb:(location)=>{
            this.selectedLocation = location.location_name;

or assign the lexical this to a variable (like self) the old way and use that variable if you don't want to lose the this inside the function

或者将lexical分配给变量(如self)旧方法并使用该变量如果你不想在函数内部丢失它

showLocationsDropdown(event){
    console.log("locations");
    var self = this; //<-- assign here
    let popover = this.popoverController.create(LocationsPopover,{
      cb:function(location){
        self.selectedLocation = location.location_name; //<-- use here