how does is it possible that post is accessible in my controller? - angularjs

Question

how is it possible that i can do $scope.post = post; and that i did not have to do $scope.post = posts.post;
app.js
angular.module('flapperNews', ['templates','ui.router'])
.config([
'$stateProvider',
'$urlRouterProvider',
function($stateProvider, $urlRouterProvider) {
$stateProvider
.state('home', {
url: '/home',
templateUrl: 'home/_home.html',
controller: 'MainCtrl',
resolve: {
postPromise: ['posts', function(posts){
return posts.getAll();
}]
}
})
.state('posts', {
url: '/posts/{id}',
templateUrl: 'posts/_posts.html',
controller: 'PostsCtrl',
resolve: {
post: ['$stateParams', 'posts', function($stateParams, posts) {
return posts.get($stateParams.id);
}]
}
});
$urlRouterProvider.otherwise('home');
}])
postCtrl.js
angular.module('flapperNews')
.controller('PostsCtrl', [
'$scope',
'posts',
'post',
function($scope, posts, post){
$scope.post = post;
$scope.addComment = function(){
if($scope.body === '') { return; }
$scope.post.comments.push({
body: $scope.body,
author: 'user',
upvotes: 0
});
$scope.body = '';
};
}]);

Answer 1

That's pretty simple.
You wrote in declaration of your posts state:
resolve: {
post: ['$stateParams', 'posts', function($stateParams, posts) {
return posts.get($stateParams.id);
}]
}
You inject in this function your posts service and make a call (to some API, whatever). This function returns promise. Property resolve in state declaration at first will wait for resolving all promises which has been written in there. And after that it will inject the results of all resolved promises into the controller.
Lets take a look on your controller:
angular.module('flapperNews')
.controller('PostsCtrl', [
'$scope',
'posts',
'post',
function($scope, posts, post){
$scope.post = post;
...
};
}]);
On injection section we can see posts - injected service. Also post - which will be a resolved promises which came from resolve section of your state.
It means that you don't have to call your posts service again, because it was already called before instantiating the controller. You probably don't need to inject this service at all.
I hope I clarified that and it will help you to understand.