[AngularJS] ANGULARJS Series (7) The promise of advanced article

Directory

• Using Promise
• Then chain
• Extended

In the previous section, we used then in HTTP and returned a ' lingering object ' in Ngresource.

This section describes the promise in angular.

I think the promise in JS can be likened to the await of a task in C # to implement callbacks when synchronizing.

Using Promise

Html

    <input type= "checkbox" ng-model= "flag"/>    <button ng-click= "func ()" >Test</button>

Controller

[' $scope ', ' $q ', function (scope, q) {            scope.func = function () {                var defer = Q.defer ();//create 1 lazy load objects or new 1 units of work 
   var promise = Defer.promise;//defer The core of the object contains a handle to the callback function                Promise.then (function (data) {                    var msg = ' success: ' + data;                    Console.log (msg);                }, function (data) {                    var msg = ' failed: ' + data;                    Console.log (msg);                }, function (data) {                    var msg = ' Notification: ' + data;                    Console.log (msg);                });                Defer.notify (' Start execution ');                Scope.flag? Defer.resolve (' checked '): Defer.reject (' unchecked ');            }
}]

Click the button:

Here we can see how $q the defer() method created by the object has

• resolve(value): Used to execute deferred promise , value can be a string, object, etc.
• reject(value): Used to reject deferred promise , value can be a string, object, etc.
• notify(value): Gets deferred promise the execution state, and then uses this function to pass it.
• then(successFunc, errorFunc, notifyFunc): Whether it promise succeeds or fails, when the result is available, it is then immediately called asynchronously successFunc , or ' Errorfunc ', and promise may be called 0 to several times before being executed or rejected notifyFunc to provide a hint of the process state.
• catch(errorFunc)
• finally(callback)

Then chain

We changed the code slightly (this code is incomplete and only defines the success method).

            SCOPE.FUNC2 = function () {                var defer = Q.defer ();                var promise = Defer.promise;                Promise.then (function (data) {                    var msg = ' success: ' + data;                    return msg;                }). Then (function (data) {                    console.log (data);                });                Defer.notify (' Start execution ');                Scope.flag? Defer.resolve (' checked '): Defer.reject (' unchecked ');            }

Here to illustrate the then function and the Reject function. Let's see the demo.

                Promise.then (function (data) {                    var msg = ' success: ' + data;                    return msg;                }, function (data) {                    var msg = ' failed: ' + data;                    return msg;                }). Then (function (data) {                    console.log (data);                }, Function (Erro) {                    console.log (' Erro: ' + Erro);                });

The Erro prefix is added to the Erro function in the second then.

We find that this method is not called.

After modifying the promise:

                Promise.then (function (data) {                    var msg = ' success: ' + data;                    return msg;                }). Then (function (data) {                    console.log (data);                }, Function (Erro) {                    console.log (' Erro: ' + Erro);                });

You can also return to promise

                Promise.then (function () {                    var thendefer = Q.defer ();                    $timeout (function () {                        if (scope.flag)                            thendefer.resolve (' done success ');                        Thendefer.reject (' Done faild ');                    };                    return thendefer.promise;                }). Then (function (data) {                    console.log (data);                }, Function (Erro) {                    console.log (' Erro: ' + Erro);                });

• The Promise chain will pass the previous then return result to the next then (if not undefined) of the call chain.
• If you then return a Promise object, the next one then will only be called when the promise is processed.
• catchprovides an exception-handling point for the entire chain at the end of the chain

• The end of the chain finally will always be executed, regardless of whether the promise is processed or rejected, and the cleanup function

Extended

$q.all(), allowing you to wait for parallel promise processing, when all promise are processed, call a common callback

$q.when(), if you want to create a promise with a common variable

This address: http://www.cnblogs.com/neverc/p/5928285.html

[AngularJS] ANGULARJS Series (7) The promise of advanced article