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JavaScript AngularJS Basics (1.x) Services in Angular Using Services To Save and Delete Data

Posted by Yang Li
Yang Li
290 Points

difference btw dataService.helloConsole and dataService.deleteTodos??

I kind of got why getTodos have the callback function. since It's not a easy function. like f1().then(f2). after f1() executed successfully, then we get to do f2.

but for deleteTodos? I feel like this is as easy as HelloWorldConsole.

Why can we just use $scope.deletetodo = dataService.deletdTodo; ??

Why should I still use something like a callback for this function?

1 Answer

Lorenzo Pieri
Lorenzo Pieri
19,772 Points
Lorenzo Pieri
Lorenzo Pieri
19,772 Points

Hello! deleteTodo is not making a callback, there are just two parameters passed to it. Read the comments in the code below!

angular.module("todoListApp", [])

.controller('mainCtrl', function($scope, dataService) {
  $scope.learningNgChange = function() {
    console.log("An input changed!");
  };

  $scope.helloWorld = dataService.helloWorld;

  dataService.getTodos(function(response) { 
      console.log(response.data);  
      $scope.todos = response.data;
// This one requires a callback because it's waiting for a response from a server
    });

  $scope.deleteTodo = function(todo, $index) {
// $index is a parameter passed from the view when you ng-click
// todo is the element in the $scope that you want to delete
    dataService.deleteTodo(todo);
    $scope.todos.splice($index, 1);
// this one doesn't need a callback because it's writing to the server, not waiting for anything
  };

  $scope.saveTodo = function(todo) {
    dataService.saveTodo(todo);
// same, sending something to a server, not receiving somthing.
  };
})
.service('dataService', function($http) {
  this.helloWorld = function() {
    console.log("This is the data service's method!!");
  };

  this.getTodos = function(callback){
    $http.get('mock/todos.json')
    .then(callback)
  };

  this.deleteTodo = function(todo) {
    console.log("The " + todo.name + " todo has been deleted!")
    // other logic that sends a request for DELETE to database
  };

  this.saveTodo = function(todo) {
    console.log("The " + todo.name + " todo has been saved!");
    // other logic... that sends a POST request (or GET) to database
  };

});