Angular - this.function is not a function

Question

I'm a bit desperate with this. I have a component that takes data and renders a map with the information of this data. All fine here. I put markers on this map and I want to do a click function in the marker. Those function call another function defined in the component and bring me data to show it in a modal. But, when I click the marker, I receive this error:

this.getInfoAlteracion is not a function

I don't know why. I prove a lot of things but I can't see the error. Here's my code:

import { Component, OnInit } from '@angular/core';
import * as L from 'leaflet';
import 'leaflet.markercluster';
import { MapService } from './services';
import * as global from 'app/globals';
import { Alteracion } from './dto/alteracion';

@Component({
  selector: 'map',
  templateUrl: './map.component.html',
  styleUrls: ['./map.component.scss']
})
export class MapComponent implements OnInit {
  public alteraciones: Alteracion[] = [];
  public alteracion: Alteracion[] = [];

  constructor(private mapService: MapService) {}

  ngOnInit() {
    this.getAlteraciones();
  }


  getAlteraciones() {
    this.mapService.getListAlteraciones(11, 1).subscribe(
      result => {
        this.alteraciones = result;
        this.renderMap();
      },
      err => console.log(err)
    );
  }

  getInfoAlteracion(id_alteracion: string) {
    this.mapService.getInfoAlteracion(id_alteracion).subscribe(
      result => {
        this.alteracion = result;
        console.log(this.alteracion);
      },
      err => console.log(err)
    );
  }

  renderMap() {
    L.Icon.Default.imagePath = 'assets/img/theme/vendor/leaflet/';
    let map: any;

      map = L.map('map', {
            zoomControl: false,
            format: 'image/jpeg',
            center: L.latLng(40.4166395, -3.7046087),
            zoom: 2,
            minZoom: 0,
            maxZoom: 19,
            layers: [this.mapService.baseMaps.Esri]});

      L.control.zoom({ position: 'topleft' }).addTo(map);
      L.control.layers(this.mapService.baseMaps).addTo(map);

    let cluster = L.markerClusterGroup();

    for (let al of this.alteraciones) {
      let marker = L.marker([al.coory, al.coorx]);

      marker.on('click', function(e) {
        alert('Id alteración: ' + al.id_alteracion); // THIS WORKS
        this.getInfoAlteracion(al.id_alteracion); // THIS DON'T WORK
        console.log(this.alteracion);
      });

      cluster.addLayer(marker);
    }
    map.addLayer(cluster);   

}

Any ideas? Thanks in advance!

Titian Cernicova-Dragomir · Accepted Answer · 2018-02-15T13:43:19.763

You need to use an arrow function for your event handler

  marker.on('click', (e) => {
    alert('Id alteración: ' + al.id_alteracion); // THIS WORKS
    this.getInfoAlteracion(al.id_alteracion); // THIS DON'T WORK
    console.log(this.alteracion);
  });

In Javascript & Typescript this is determined by the caller for a function. Arrow functions capture this from the declaration site. Quite simply this way not what you expected it to be.

score 3 · Answer 2 · answered Feb 15 '18 at 13:52

Please try like this

import { Component, OnInit } from '@angular/core';
import * as L from 'leaflet';
import 'leaflet.markercluster';
import { MapService } from './services';
import * as global from 'app/globals';
import { Alteracion } from './dto/alteracion';

@Component({
  selector: 'map',
  templateUrl: './map.component.html',
  styleUrls: ['./map.component.scss']
})
export class MapComponent implements OnInit {
  public alteraciones: Alteracion[] = [];
  public alteracion: Alteracion[] = [];

  constructor(private mapService: MapService) {}

  ngOnInit() {
    this.getAlteraciones();
  }


  getAlteraciones() {
    this.mapService.getListAlteraciones(11, 1).subscribe(
      result => {
        this.alteraciones = result;
        this.renderMap();
      },
      err => console.log(err)
    );
  }

  getInfoAlteracion(id_alteracion: string) {
    this.mapService.getInfoAlteracion(id_alteracion).subscribe(
      result => {
        this.alteracion = result;
        console.log(this.alteracion);
      },
      err => console.log(err)
    );
  }

  renderMap() {
      const reference=this; // code added
    L.Icon.Default.imagePath = 'assets/img/theme/vendor/leaflet/';
    let map: any;

      map = L.map('map', {
            zoomControl: false,
            format: 'image/jpeg',
            center: L.latLng(40.4166395, -3.7046087),
            zoom: 2,
            minZoom: 0,
            maxZoom: 19,
            layers: [this.mapService.baseMaps.Esri]});

      L.control.zoom({ position: 'topleft' }).addTo(map);
      L.control.layers(this.mapService.baseMaps).addTo(map);

    let cluster = L.markerClusterGroup();

    for (let al of this.alteraciones) {
      let marker = L.marker([al.coory, al.coorx]);

      marker.on('click', function(e) {
        alert('Id alteración: ' + al.id_alteracion); 
        reference.getInfoAlteracion(al.id_alteracion); // code updated
        console.log(this.alteracion);
      });

      cluster.addLayer(marker);
    }
    map.addLayer(cluster);   

}

Why not just use arrow functions if we are using Typescript anyway ? — Titian Cernicova-Dragomir, Feb 15 '18 at 13:55

Angular - this.function is not a function

2 Answers2

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