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docs(q): documentation for all $q apis

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commit 174952e443bc98e9df6afcdc3e0cec81412e5fd1 1 parent 6f91ffe
@IgorMinar IgorMinar authored
Showing with 171 additions and 4 deletions.
  1. +171 −4 src/Deferred.js
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175 src/Deferred.js
@@ -1,10 +1,6 @@
'use strict';
/**
- * inspired by Kris Kowal's Q (https://github.com/kriskowal/q)
- */
-
-/**
* Constructs a promise manager.
*
* @param {function(function)=} nextTick Function for executing functions in the next turn. Falls
@@ -26,6 +22,16 @@ function qFactory(nextTick, exceptionHandler) {
}
}
+
+ /**
+ * @ngdoc
+ * @name angular.module.ng.$q#defer
+ * @methodOf angular.module.ng.$q
+ * @description
+ * Creates a `Deferred` object which represents a task which will finish in the future.
+ *
+ * @returns {Deferred} Returns a new instance of deferred.
+ */
var defer = function() {
var pending = [],
value, deferred;
@@ -107,6 +113,41 @@ function qFactory(nextTick, exceptionHandler) {
};
+ /**
+ * @ngdoc
+ * @name angular.module.ng.$q#reject
+ * @methodOf angular.module.ng.$q
+ * @description
+ * Creates a promise that is resolved as rejected with the specified `reason`. This api should be
+ * used to forward rejection in a chain of promises. If you are dealing with the last promise in
+ * a promise chain, you don't need to worry about it.
+ *
+ * When comparing deferreds/promises to the familiar behavior of try/catch/throw, think of
+ * `reject` as the `throw` keyword in JavaScript. This also means that if you "catch" an error via
+ * a promise error callback and you want to forward the error to the promise derived from the
+ * current promise, you have to "rethrow" the error by returning a rejection constructed via
+ * `reject`.
+ *
+ * <pre>
+ * promiseB = promiseA.then(function(result) {
+ * // success: do something and resolve promiseB
+ * // with the old or a new result
+ * return result;
+ * }, function(reason) {
+ * // error: handle the error if possible and
+ * // resolve promiseB with newPromiseOrValue,
+ * // otherwise forward the rejection to promiseB
+ * if (canHandle(reason)) {
+ * // handle the error and recover
+ * return newPromiseOrValue;
+ * }
+ * return $q.reject(reason);
+ * });
+ * </pre>
+ *
+ * @param {*} reason Constant, message, exception or an object representing the rejection reason.
+ * @returns {Promise} Returns a promise that was already resolved as rejected with the `reason`.
+ */
var reject = function(reason) {
return {
then: function(callback, errback) {
@@ -120,6 +161,21 @@ function qFactory(nextTick, exceptionHandler) {
};
+ /**
+ * @ngdoc
+ * @name angular.module.ng.$q#when
+ * @methodOf angular.module.ng.$q
+ * @description
+ * Wraps an object that might be a value or a (3rd party) then-able promise into a $q promise.
+ * This is useful when you are dealing with on object that might or might not be a promise, or if
+ * the promise comes from a source that can't be trusted.
+ *
+ * @param {*} value Value or a promise
+ * @returns {Promise} Returns a single promise that will be resolved with an array of values,
+ * each value coresponding to the promise at the same index in the `promises` array. If any of
+ * the promises is resolved with a rejection, this resulting promise will be resolved with the
+ * same rejection.
+ */
var when = function(value, callback, errback) {
var result = defer(),
done;
@@ -168,6 +224,20 @@ function qFactory(nextTick, exceptionHandler) {
}
+ /**
+ * @ngdoc
+ * @name angular.module.ng.$q#all
+ * @methodOf angular.module.ng.$q
+ * @description
+ * Combines multiple promises into a single promise that is resolved when all of the input
+ * promises are resolved.
+ *
+ * @param {Array.<Promise>} promises An array of promises.
+ * @returns {Promise} Returns a single promise that will be resolved with an array of values,
+ * each value coresponding to the promise at the same index in the `promises` array. If any of
+ * the promises is resolved with a rejection, this resulting promise will be resolved with the
+ * same rejection.
+ */
function all(promises) {
var deferred = defer(),
counter = promises.length,
@@ -195,6 +265,103 @@ function qFactory(nextTick, exceptionHandler) {
};
}
+/**
+ * @ngdoc service
+ * @name angular.module.ng.$q
+ * @requires $rootScope
+ *
+ * @description
+ * A promise/deferred implementation inspired by [Kris Kowal's Q](https://github.com/kriskowal/q).
+ *
+ * [The CommonJS Promise proposal](http://wiki.commonjs.org/wiki/Promises) describes a promise as an
+ * interface for interacting with an object that represents the result of an action that is
+ * performed asynchronously, and may or may not be finished at any given point in time.
+ *
+ * When it comes to error handling, deferred and promise apis are to asynchronous programing what
+ * `try`, `catch` and `throw` keywords are to synchronous programing.
+ *
+ * <pre>
+ * function asyncGreet(name) {
+ * var deferred = $q.defer();
+ *
+ * setTimeout(function() {
+ * if (okToGreet(name)) {
+ * deferred.resolve('Hello, ' + name + '!');
+ * } else {
+ * deferred.reject('Greeting ' + name + ' is not allowed.');
+ * }
+ * }, 1000);
+ *
+ * return deferred.promise;
+ * }
+ *
+ * var promise = asyncGreet('Robin Hood');
+ * promise.then(function(greeting) {
+ * alert('Success: ' + greeting);
+ * }, function(reason) {
+ * alert('Failed: ' + reason);
+ * );
+ * </pre>
+ *
+ * At first it might not be obvious why this extra complexity is worth the trouble. The payoff
+ * comes in the way of
+ * [guarantees that promise and deferred apis make](https://github.com/kriskowal/uncommonjs/blob/master/promises/specification.md).
+ *
+ * Additionally the promise api allows for composition that is very hard to do with the
+ * traditional callback ([CPS](http://en.wikipedia.org/wiki/Continuation-passing_style)) approach.
+ * For more on this please see the [Q documentation](https://github.com/kriskowal/q) especially the
+ * section on serial or paralel joining of promises.
+ *
+ *
+ * # The Deferred API
+ *
+ * A new instance of deferred is constructed by calling `$q.defer()`.
+ *
+ * The purpose of the deferred object is to expose the associated Promise instance as well as api's
+ * that can be used for singnaling the successful or unsucessful completion of the task.
+ *
+ * **Methods**
+ *
+ * - `resolve(value)` – resolves the derived promise with the `value`. If the value is a rejection
+ * constructed via `$q.reject`, the promise will be rejected instead.
+ * - `reject(reason)` – rejects the derived promise with the `reason`. This is equivalent to
+ * resolving it with a rejection constructed via `$q.reject`.
+ *
+ * **Properties**
+ *
+ * - promise – `{Promise}` – promise object associated with this deferred.
+ *
+ *
+ * # The Promise API
+ *
+ * A new promise instance is created when a deferred instance is created and can be retrieved by
+ * calling `deferred.promise`.
+ *
+ * The purpose of the promise object is to allow for interested parties to get access to the result
+ * of the deferred task when it completes.
+ *
+ * **Methods**
+ *
+ * - `then(successCallback, errorCallback)` – regardless of when the promise was or will be resolved
+ * or rejected calls one of the success or error callbacks asynchronously as soon as the result
+ * is available.
+ *
+ * This method *returns a new promise* which is resolved or rejected via the return value of the
+ * `successCallback` or `errorCallback`.
+ *
+ *
+ * # Differences betweeb Kris Kowal's Q and $q
+ *
+ * There are three main differences:
+ *
+ * - $q is integrated with the {@link angular.module.ng.$rootScope.Scope} Scope model observation
+ * mechanism in angular, which means faster propagation of resolution or rejection into your
+ * models and avoiding unnecessary browser redraws, which would result in flickering UI.
+ * - $q promises are reconginized by the templating engine in angular, which means that in templates
+ * you can treat promises attached to a scope as if they were the resulting values.
+ * - Q has many more features that $q, but that comes at a cost of bytes. $q is tiny, but contains
+ * all the important functionality needed for common async tasks.
+ */
// TODO(i): move elsewhere
function $QProvider() {
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