AngularJS what is difference between $http success and then - angularjs

Question

various people use $http different way. say sample 1
$http({
method: 'GET',
url: 'api/book/',
cache: $templateCache
}).
success(function (data, status, headers, config) {
$scope.books = data;
}).
error(function (data, status) {
console.log("Request Failed");
});
here success and error callback is there to notify user. again few people use $http different way like
this.getMovie = function(movie) {
return $http.get('/api/v1/movies/' + movie)
.then(
function (response) {
return {
title: response.data.title,
cost: response.data.price
});
},
function (httpError) {
// translate the error
throw httpError.status + " : " +
httpError.data;
});
};
here then is using.......is it promise sample ? why people would then instead of success ? what is the advantage of then ?
what is the meaning of promise and what promise does ?
when to use promise in angular ?

Answer 1

Per angular DOCS, looks like 1.4.4 is the first version to have the notice(see below).
Deprecation Notice
The $http legacy promise methods success and error have been
deprecated. Use the standard then method instead. If
$httpProvider.useLegacyPromiseExtensions is set to false then these
methods will throw $http/legacy error.
From the docs, the new preferred angular way to do all $http requests.(code from angular docs)
General usage
The $http service is a
function which takes a single argument— a configuration object— that is used to generate an HTTP request and returns a promise.
// Simple GET request example :
$http.get('/someUrl').
then(function(response) {
// this callback will be called asynchronously
// when the response is available
}, function(response) {
// called asynchronously if an error occurs
// or server returns response with an error status.
});
// Simple POST request example (passing data) :
$http.post('/someUrl', {
msg: 'hello word!'
}).
then(function(response) {
// this callback will be called asynchronously
// when the response is available
}, function(response) {
// called asynchronously if an error occurs
// or server returns response with an error status.
});
SO resource
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