지연된 객체 란 무엇입니까?

지연된 객체 란 무엇입니까?

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jQuery 1.5는 "Deferred Objects"를 추가합니다. 그들은 무엇이며 정확히 무엇을합니까?

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지연된 객체

jQuery 1.5부터 Deferred 객체는 여러 개의 콜백을 자체 관리 콜백 큐에 등록하고, 콜백 큐를 적절하게 호출하며, 동기 또는 비동기 함수의 성공 또는 실패 상태를 릴레이하는 방법을 제공합니다.

지연된 방법 :

• deferred.done ()
  • 지연된 오브젝트가 분석 될 때 호출 될 핸들러를 추가하십시오.
• deferred.fail ()
  • 지연된 오브젝트가 거부 될 때 호출 될 핸들러를 추가하십시오.
• deferred.isRejected ()
  • 지연된 오브젝트가 거부되었는지 판별하십시오.
• deferred.isResolved ()
  • 지연된 오브젝트가 해결되었는지 판별하십시오.
• deferred.reject ()
  • 지연된 객체를 거부하고 주어진 인수로 failCallbacks를 호출하십시오.
• deferred.rejectWith ()
  • 지연된 객체를 거부하고 지정된 컨텍스트 및 인수로 failCallbacks를 호출하십시오.
• deferred.resolve ()
  • Deferred 객체를 해결하고 주어진 인수로 doneCallback을 호출합니다.
• deferred.resolveWith ()
  • Deferred 객체를 해결하고 주어진 컨텍스트 및 인수로 doneCallbacks를 호출하십시오.
• deferred.then ()
  • 지연된 오브젝트가 해결되거나 거부 될 때 호출 될 핸들러를 추가하십시오.

연기 된 연기 :

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

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

그리고 기존 ajax () 메소드 콜백은 설정에서 선언되지 않고 연결될 수 있습니다.

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

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Eric Hynds 블로그 게시물의 작업 예 : http://jsfiddle.net/ehynds/Mrqf8/

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jqXHR

jQuery 1.5부터 $ .ajax () 메소드는 XMLHTTPRequest 객체의 상위 집합 인 jXHR 객체를 반환합니다. 자세한 정보는 $ .ajax 항목의 jXHR 섹션을 참조하십시오.

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에서 JQUERY 1.5을 발표했다 :

지연된 개체

Ajax 모듈을 다시 작성하면서 새로운 기능인 Deferred Objects 도 공개되었습니다 . 이 API를 사용하면 즉시 존재하지 않을 수있는 리턴 값 (예 : 비동기 Ajax 요청의 리턴 결과)에 대해 작업 할 수 있습니다. 또한 여러 이벤트 핸들러 (Ajax API에서는 불가능했던 것)를 연결할 수 있습니다.

또한 노출 된 jQuery.Deferred를 사용하여 자신의 지연된 객체를 만들 수 있습니다. 이 API에 대한 자세한 정보는 지연된 오브젝트 문서 에서 찾을 수 있습니다 .

Eric Hynds는 jQuery 1.5에서 Deferreds 사용 에 대한 좋은 튜토리얼을 작성했습니다 .

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그 다음에 그 기능을 설명하고 그 기능을 설명하고 설명하겠습니다.

jQuery 1.5의 관련 소스 사본. 나는 의견이 대부분 맞다고 생각합니다.

이것은 유익 할 수 있습니다

// 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;
},

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내가 틀렸다면 나를 수정하십시오. 그러나 최근에는 기본적으로 비동기 작업 실행기라고 클릭했습니다. 약속은 결과 계약으로, 무언가를받을 수 있도록 보장하지만 언제받을 수 있는지 보장 할 수는 없습니다.

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While working in Javascript, we encounter situation where function calls are asynchronous. That is the calee function's (let say X) flow does not wait for the called asynchronous function (Let say Y). Typical example is when we make calls to a server to fetch some data from a database or an HTML page. If those calls were not asynchronous, the user interface will be stuck waiting for the server to respond. This asynchronous nature leads to a problem when you want to execute things in an order, for example, you want to print something after Y (asynch) is done executing or done fetching data. Here jQuery provide us with Deffered Object. Basically, jQuery has taken care of all boilerplate code that usually we write to resolve this situation. Here is a simple example:

  $.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

You can write your own deferred (asynch) function

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
})

I hope this helped.

참고URL : https://stackoverflow.com/questions/4866721/what-are-deferred-objects