jQuery Promise is undefined

jQuery Promise is undefined

本文关键字：undefined is Promise jQuery      更新时间：2023-09-26

我正在尝试使用jQuery的promise对象，以确保在其他代码运行之前完成异步调用。我需要使用Deferred对象，因为我使用SharePoint的executeQueryAsync来运行查询。我在这里使用Shereen Qumsieh的例子。

我的问题是，在结果处理程序中，jQuery promise总是未定义的，我无法确定原因。以前有人经历过这种情况吗？任何能为我指明正确方向的帮助或线索都将不胜感激。谢谢

查询

function successCallback() {
            console.log(this.d.promise());
            this.d.resolve(this.list);
        }
        function failCallback() {
            console.log(this.d.promise());
            this.d.reject("something bad happened");
        }
        function getMyList() {
            var d = jQuery.Deferred();
            console.log(d.promise());
            var clientContext = SP.ClientContext.get_current();
            var list = clientContext.get_web().get_lists().getByTitle('Documents');
            clientContext.load(list);
            var o = {d: d, list:list};
            clientContext.executeQueryAsync(Function.createDelegate(o, successCallback), Function.createDelegate(o, failCallback));
            return d.promise();
        }

结果处理程序

var result = getMyList();
console.log(result);// output: undefined
        result.done(function(result) { //TypeError: Cannot read property 'done' of undefined
            // result is an SP.List because that is what we passed to resolve()!
            var list = result;
            console.log('Result done hit. result: ' + result);
        });
        result.fail(function(result) {
            // result is a string because that is what we passed to reject()!
            var error = result;
            console.log('Result fail hit. result: ' + error);
        });

更新：

getMyList console.log（d.promise（））输出

Object {state: function, always: function, then: function, promise: function, pipe: function…}

successCallback console.log（this.d.promise（））输出

Object {state: function, always: function, then: function, promise: function, pipe: function…}

结果处理程序控制台.log（结果）输出

undefined

带时间戳的顺序输出

getMyList ln 449 Promise output 1412279244379: [object Object]
getMyList ln 458 Promise output 1412279244390: [object Object]
Result output 1412279244392: undefined
Result Handler Error time: 1412279244392: TypeError: Cannot read property 'done' of undefined
successCallback Promise output 1412279244569: [object Object] 
successCallback Resolve output 1412279244570: [object Object]

仍然不确定问题的确切根本原因，但我确实找到了解决方案。实现该解决方案的主要区别有两个。首先，我使用了SP.RequestExecutor而不是SP.ClientContext.executeQueryAsync。然后按照@Roamer-1888的建议，去掉Function.createDelegate()的废话。SP.ClientContext.executeQueryAsync不断返回一个从未真正解析过的SP.ClientRequest对象，而Function.createDelegate则对promise对象进行了一些奇怪的作用域。还是不确定。

       var def = new jQuery.Deferred();
        var executor = new SP.RequestExecutor(_spPageContextInfo.siteAbsoluteUrl);
        var data = "{ '__metadata': { 'type': 'SP.Data.ListItemEntityTypeFullName' },"
                + "'Title': '" + Title + "',"
                + "'Body': '" + Body+ "'}";

        executor.executeAsync({
          url: _spPageContextInfo.siteAbsoluteUrl + "/_api/web/lists(guid'<enter_guid_here>')/items",
          method: "POST",
          body: data,
          headers: { 
            "accept": "application/json;odata=verbose",
            "content-type": "application/json;odata=verbose"
          },
          success: CsomSuccess,
          error: CsomFail
        });

        function CsomSuccess(result){
            def.resolve(result);
        }
        function CsomFail(data, errorCode, errorMessage){
            def.reject('Failed to get host site. Error:' + errorMessage);
        }
        return def.promise();
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