Cannot read property 'fileChangeEvent' of undefined In Angular2 - node.js

Question

Getting this error while choosing image file
import {Injectable} from '#angular/core';
#Injectable()
export class UploadPhotoService {
filesToUpload: Array<File>;
constructor() {
this.filesToUpload = [];
}
upload() {
this.makeFileRequest("rest/api/upload", [], this.filesToUpload).then((result) => {
console.log(result);
}, (error) => {
console.error(error);
});
}
fileChangeEvent(fileInput: any){
this.filesToUpload = <Array<File>> fileInput.target.files;
}
makeFileRequest(url: string, params: Array<string>, files: Array<File>) {
return new Promise((resolve, reject) => {
var formData: any = new FormData();
var xhr = new XMLHttpRequest();
for(var i = 0; i < files.length; i++) {
formData.append("uploads[]", files[i], files[i].name);
}
xhr.onreadystatechange = function () {
if (xhr.readyState == 4) {
if (xhr.status == 200) {
alert("Upload successful!");
} else {
reject(xhr.response);
}
}
}
xhr.open("POST", url, true);
xhr.setRequestHeader("Authorization", "Bearer "+localStorage.getItem("token"));
xhr.send(formData);
});
}
}
<div class="field">
<label>Upload Photo</label>
<input type="file" (change)="uploadPhotoService.fileChangeEvent($event)" />
<button type="button" (click)="uploadPhotoService.upload()" class="ui mini button">Upload</button>
</div>
After choosing image file it showing the above error , Is there any other way to upload image file in angular2.. Please help on that too, and its giving EXCEPTION: Error in ./AddAdvertComponent class AddAdvertComponent - inline template:30:2 caused by: Cannot read property 'fileChangeEvent' of undefined
ORIGINAL EXCEPTION: Cannot read property 'fileChangeEvent' of undefined

Answer 1

throwing error
ORIGINAL EXCEPTION: Cannot read property 'fileChangeEvent' of undefined
because you are calling fileChangeEvent not correctly or your uploadPhotoService have not definer, you have to call it like this
if the method is in the same class
<input type="file" (change)="fileChangeEvent($event)" />
or if your method is in some different class or in some service than make sure you initilize that service in the constructor like this
constructor(prive uploadPhotoService: UploadPhotoService) { }
than you are able to use like this
<input type="file" (change)="uploadPhotoService.fileChangeEvent($event)" />