遅延オブジェクトとは何ですか？

jQuery 1.5は「遅延オブジェクト」を追加します。彼らは何であり、彼らは正確には何をしますか？

遅延オブジェクト

jQuery 1.5以降、Deferredオブジェクトは、複数のコールバックを自己管理のコールバックキューに登録し、必要に応じてコールバックキューを呼び出し、同期または非同期関数の成功または失敗の状態を中継する方法を提供します。

遅延メソッド：

• deferred.done（）
  • Deferredオブジェクトが解決されたときに呼び出されるハンドラーを追加します。
• deferred.fail（）
  • Deferredオブジェクトが拒否されたときに呼び出されるハンドラーを追加します。
• deferred.isRejected（）
  • Deferredオブジェクトが拒否されたかどうかを確認します。
• deferred.isResolved（）
  • Deferredオブジェクトが解決されたかどうかを確認します。
• deferred.reject（）
  • Deferredオブジェクトを拒否し、指定した引数を使用してfailCallbacksを呼び出します。
• deferred.rejectWith（）
  • Deferredオブジェクトを拒否し、指定されたコンテキストと引数でfailCallbacksを呼び出します。
• deferred.resolve（）
  • Deferredオブジェクトを解決し、指定された引数を使用してdoneCallbackを呼び出します。
• deferred.resolveWith（）
  • Deferredオブジェクトを解決し、指定されたコンテキストと引数でdoneCallbacksを呼び出します。
• deferred.then（）
  • Deferredオブジェクトが解決または拒否されたときに呼び出されるハンドラーを追加します。

延期中：

$.get("test.php").done(
    function(){ alert("$.get succeeded"); }
);

$.get("test.php")
    .done(function(){ alert("$.get succeeded"); })
    .fail(function(){ alert("$.get failed!"); });

また、既存のajax（）メソッドのコールバックは、設定で宣言するのではなく、連鎖させることができるようです。

var jqxhr = $.ajax({ url: "example.php" })
    .success(function() { alert("success"); })
    .error(function() { alert("error"); })
    .complete(function() { alert("complete"); });

Eric Hyndsブログの投稿の実際の例：http : //jsfiddle.net/ehynds/Mrqf8/

jqXHR

jQuery 1.5以降、$。ajax（）メソッドは、XMLHTTPRequestオブジェクトのスーパーセットであるjXHRオブジェクトを返します。詳細については、$。ajaxエントリのjXHRセクションを参照してください。

JQUERY 1.5からリリース：

遅延オブジェクト

Ajaxモジュールの書き直しに加えて、同じく公開された新しい機能が導入されました：Deferred Objects。このAPIを使用すると、すぐには存在しない可能性のある戻り値（非同期Ajax要求からの戻り結果など）を処理できます。さらに、複数のイベントハンドラー（以前はAjax APIでは不可能であったもの）をアタッチする機能を提供します。

さらに、公開されたjQuery.Deferredを使用して、独自の遅延オブジェクトを作成できます。このAPIの詳細については、遅延オブジェクトのドキュメントをご覧ください 。

Eric HyndsがjQuery 1.5でのDeferredの使用に関する優れたチュートリアルを作成しました。

それでは、それが何であるかを説明するのではなく、それが何であるかを示し、説明します。

jQuery 1.5の関連ソースのコピーで、何をしているのかを説明する注釈が付いています。コメントはほぼ正しいと思います。

これは有益かもしれません

// promiseMethods. These are the methods you get when you ask for a promise.
// A promise is a "read-only" version
// fullMethods = "then done fail resolve resolveWith reject rejectWith isResolve    isRejected promise cancel".split(" ")
// As you can see it removes resolve/reject so you can't actaully trigger a
// anything on the deferred object, only process callbacks when it "finishes".
promiseMethods = "then done fail isResolved isRejected promise".split(" "),

// Create a simple deferred (one callbacks list)
/* Class: _Deferred.
 *  methods: done, resolve, resolveWith, isResolved
 *  internal method: cancel
 *
 *  Basically allows you to attach callbacks with the done method.
 *  Then resolve the deferred action whenever you want with an argument.
 *  All the callbacks added with done will be called with the resolved argument
 *  Any callbacks attached after resolvement will fire immediatly.
 *
 *  resolveWith allows you to set the this scope in the callbacks fired.
 *
 *  isResolved just checks whether it's resolved yet.
 *
 *  cancel blocks resolve/resolveWith from firing. the methods added throug
 *  done will never be called
 */
_Deferred: function () {
    var // callbacks list
    callbacks = [],
        // stored [ context , args ]
        // stores the context & args that .resolve was called with
        fired,
        // to avoid firing when already doing so
        firing,
        // flag to know if the deferred has been cancelled
        // in Deferred cancel gets called after the first resolve call
        cancelled,
        // the deferred itself
        deferred = {

            // done( f1, f2, ...)
            done: function () {
                if (!cancelled) {
                    var args = arguments,
                        i, length,
                        // elem in callback list
                        elem,
                        // type of elem in callback list
                        type,
                        // cached context & args for when done is called
                        // after resolve has been
                        _fired;
                    // If resolve has been called already
                    if (fired) {
                        // mark it locally
                        _fired = fired;
                        // set fired to 0. This is neccesary to handle
                        // how done deals with arrays recursively
                        // only the original .done call handles fired
                        // any that unwrap arrays and call recursively
                        // dont handle the fired.
                        fired = 0;
                    }
                    // for each function append it to the callback list
                    for (i = 0, length = args.length; i < length; i++) {
                        elem = args[i];
                        type = jQuery.type(elem);
                        // if argument is an array then call done recursively
                        // effectively unwraps the array
                        if (type === "array") {
                            // def.done([f1, f2, f3]) goes to
                            // def.done(f1, f2, f3) through the apply
                            deferred.done.apply(deferred, elem);
                        } else if (type === "function") {
                            // if its a function add it to the callbacks
                            callbacks.push(elem);
                        }
                    }
                    // if it's already been resolved then call resolveWith using
                    // the cahced context and arguments to call the callbacks
                    // immediatly
                    if (_fired) {
                        deferred.resolveWith(_fired[0], _fired[1]);
                    }
                }
                return this;
            },

            // resolve with given context and args
            resolveWith: function (context, args) {
                                // if its been cancelled then we can't resolve
                                // if it has fired then we can't fire again
                                // if it's currently firing then we can't fire. This check is
                // there because of the try finally block. It ensures we
                // cant call resolve between the try & finally in the catch phase.
                if (!cancelled && !fired && !firing) {
                    firing = 1;
                    // try block because your calling external callbacks
                    // made by the user which are not bugfree.
                                        // the finally block will always run no matter how bad
                                        // the internal code is.
                    try {
                        while (callbacks[0]) {
                            callbacks.shift().apply(context, args);
                        }
                                        // cache the content and arguments taht have been called
                                        // and set firing to false.
                    } finally {
                        fired = [context, args];
                        firing = 0;
                    }
                }
                return this;
            },

            // resolve with this as context and given arguments
            // just maps to resolveWith, this sets the this scope as normal
            // maps to this.promise which is the read only version of Deferred.
            resolve: function () {
                deferred.resolveWith(jQuery.isFunction(this.promise) ? this.promise() : 
this, arguments);
                return this;
            },

            // Has this deferred been resolved?
            // checks whether it's firing or if it has fired.
            isResolved: function () {
                return !!(firing || fired);
            },

            // Cancels the action. To be used internally
            cancel: function () {
                cancelled = 1;
                callbacks = [];
                return this;
            }
        };

    return deferred;
},
/* Class: Deferred.
 *  methods: then, done, fail, resolve, reject, resolveWith, rejectWith, isResolved, 
isRejected, promise
 *
 *  then is a shortcut for both assigning done & fail in one function.
 *
 *  This one has two underlying lists with different semantic meanings. You
 *  can bind to both the done callbacks and the fail callbacks then either
 *  resolve or reject your Deferred object.
 *
 *  You can check whether it has been resolved or rejected. useful to see
 *  Afterwards which one has happened.
 *
 *  Call .promise to return a new object which doesn't have the resolve/reject
 *  methods on it. This means you can only bind to it and not resolve/reject it.
 *  This is effectively read-only.
 *
 */
// Full fledged deferred (two callbacks list)
Deferred: function (func) {
        // the main deferred which deals with the success callbacks
    var deferred = jQuery._Deferred(),
                // the failure deferred which deals with the rejected callbacks
        failDeferred = jQuery._Deferred(),
                // the read only promise is cached.
        promise;
    // Add errorDeferred methods, then and promise
    jQuery.extend(deferred, {
                // def.then([f1, f2, ...], [g1, g2, ...] is a short hand for
                // def.done([f1, f2, ...])
        // def.fail([g1, g2, ...])
        then: function (doneCallbacks, failCallbacks) {
                        // fail exists here because this code will only run after
                        // deferred has been extended.
            deferred.done(doneCallbacks).fail(failCallbacks);
            return this;
        },
                // map def.fail to the second underlying deferred callback list
                // map all the other methods for rejection/failure to the underlying
                // failDeffered object so that Deferred has two callback lists stored
                // internally.
        fail: failDeferred.done,
        rejectWith: failDeferred.resolveWith,
        reject: failDeferred.resolve,
        isRejected: failDeferred.isResolved,
        // Get a promise for this deferred
        // If obj is provided, the promise aspect is added to the object
                // no clue what to do with "i"
        promise: function (obj, i /* internal */ ) {
                        // if no argument is passed then just extend promise
            if (obj == null) {
                                // if cached return the cache.
                if (promise) {
                    return promise;
                }
                                // set promise & arg to be {}
                promise = obj = {};
            }
                        // for each promiseMethods in the read only promise list
            i = promiseMethods.length;
            while (i--) {
                                // set the deferred method on the object
                obj[promiseMethods[i]] = deferred[promiseMethods[i]];
            }
                        // returns the "read-only" deferred without
                        // resolve, resolveWith, reject & rejectWith.
                        // So you cant "resolve" it but only add "done" functions
            return obj;
        }
    });
    // Make sure only one callback list will be used
        // if either resolve or reject is called cancel both.
        // this means that the one that has been called cant be called again
        // and the other one will never be called. So only the done or the fail
        // methods will ever be called
    deferred.then(failDeferred.cancel, deferred.cancel);
        // Don't mess with cancel!
    // Unexpose cancel
    delete deferred.cancel;
    // Call given func if any
        // function argument to be called. This was passed in. Allows you to
        // handle the deferred object after creating a new one, both as this scope
        // and as a new argument.
    if (func) {
        func.call(deferred, deferred);
    }
    return deferred;
},

/* Method: when
 * Arguments: none OR 1 of type(any & !deferred) OR n of type(deferred).
 *
 * If no arguments are passed then it gets resolved immediatly. A good way to
 * call multiple callback functions? Don't really know a good use of $.when()
 *
 * If one argument is passed and its not a deferred object then it resolves
 * immediatly and passes that argument to all the done callbacks attached.
 *
 * if n arguments are passed of type deferred object then the the done callbacks
 * will only fire if all of them succeed. If a single one fails then the
 * fail callbacks fire.
 *
 * Returns a promise read-only deferred object
 */
// Deferred helper
when: function (object) {
    var args = arguments,
        length = args.length,
                // If you pass in a deferred object then set deferred to be the promise
        // if you pass in anything else then set deferred to be a new deferred
        deferred = length <= 1 && object && jQuery.isFunction(object.promise) ?
                object :
                        jQuery.Deferred(),
        // cache the promise
        promise = deferred.promise(),
                // store an array
        resolveArray;

        // if multiple objects are passed in
    if (length > 1) {
                // create an arrey to store of values.
        resolveArray = new Array(length);
                // for each object that we wait on
        jQuery.each(args, function (index, element) {
                        // when that object resolves then
            jQuery.when(element).then(function (value) {
                                // store value in the array or store an array of values in it
                resolveArray[index] = arguments.length > 1 ? slice.call(arguments, 0) : 
value;
                                // if length === 1 then we finished calling them all
                if (!--length) {
                                        // resolve the deferred object with the read only promise
                                        // as context and the resolved values array as the argument
                    deferred.resolveWith(promise, resolveArray);
                }
                        // if any fail then we reject or deferred
            }, deferred.reject);
        });
        // if deferred was newly created but there was only one argument then
    // resolve it immediatly with the argument.
    } else if (deferred !== object) {
        deferred.resolve(object);
    }
        // return the read-only deferred.
    return promise;
},

私が間違っている場合は修正してください。ただし、最近は本質的に非同期タスクランナーであると最近クリックされました。約束は結果契約であり、...何かを受け取ることを保証しますが、いつ受け取るかは保証されません。

Javascriptで作業しているときに、関数呼び出しが非同期である状況が発生します。つまり、calee関数の（Xとしましょう）フローは、呼び出された非同期関数（Yとしましょう）を待機しません。典型的な例は、データベースまたはHTMLページからデータをフェッチするためにサーバーを呼び出す場合です。これらの呼び出しが非同期でない場合、ユーザーインターフェイスはサーバーが応答するのを待ってスタックします。この非同期の性質は、順番に物事を実行したい場合、たとえば、Y（非同期）の実行またはデータのフェッチが完了した後で何かを印刷したい場合に問題を引き起こします。ここで、jQueryはDeffered Objectを提供します。基本的に、jQueryは、通常この状況を解決するために作成するすべての定型コードを処理します。以下に簡単な例を示します。

  $.ajax({
      ...
  }).done(function(){
      //write here what you wish to do when this ajax call is success
  }).fail(function(){
      //write here what you wish to do on failure of this ajax call
  }); //see more on jQuery Deferred page

独自の遅延（非同期）関数を記述できます

function DoSomethingTimeConsumingAsynch(){
    var deferred = $.Deferred();

    _.defer(function(){ //I am using underscore, you can also use setTimeout
        ...  
        deferred.resolve();//When the process is done successfully 
        ...
        deferred.reject(); //When the process has failed
    });
    return deferred;
}

//HEre how to use your own asynch function
DoSomethingTimeConsumingAsynch()
.done(function(){
   //this will be invoked on success
})
.fail(function(){
   //this will be invoked on failure
})

これがお役に立てば幸いです。