Javascript Jquery Ajax 调用，不调用成功或错误

Jquery Ajax Call, doesn't call Success or Error

提问by Ruchan

Possible Duplicate:
How do I return the response from an asynchronous call?

可能的重复：
如何从异步调用返回响应？

I am using Jquery Ajax to call a service to update a value.

我正在使用 Jquery Ajax 调用服务来更新值。

function ChangePurpose(Vid, PurId) {
    var Success = false;
    $.ajax({
        type: "POST",
        url: "CHService.asmx/SavePurpose",
        dataType: "text",
        data: JSON.stringify({ Vid: Vid, PurpId: PurId }),
        contentType: "application/json; charset=utf-8",
        success: function (data) {
            Success = true;//doesn't go here
        },
        error: function (textStatus, errorThrown) {
            Success = false;//doesn't go here
        }

    });
    //done after here
    return Success;
}

and Service:

和服务：

[WebMethod]
public string SavePurpose(int Vid, int PurpId)
{
    try 
    {
        CHData.UpdatePurpose(Vid, PurpId);
        //List<IDName> abc = new List<IDName>();
        //abc.Add(new IDName { Name=1, value="Success" });
        return "Success";
    }
    catch (Exception ex)
    {
        throw new Exception(ex.Message);
    }
}

the service is being called Successfully from the AJAX. Value is also being Changed.But after the Service, success:or error:functions are not being called, in this case success should have been called but it is not working.

该服务正在从 AJAX 成功调用。价值也在改变。但是在 Service 之后，success:或error:functions are not being called，在这种情况下应该调用成功但它不起作用。

I used firebug and found that, the success or error functions are being skipped and goes directly to return Success;

我用过firebug发现，成功或错误功能被跳过并直接进入 return Success;

Can't seem to find what's the problem with the code.

似乎无法找到代码有什么问题。

Update:adding async: falsefixed the problem

更新：添加async: false修复了问题

回答by Wolf

change your code to:

将您的代码更改为：

function ChangePurpose(Vid, PurId) {
    var Success = false;
    $.ajax({
        type: "POST",
        url: "CHService.asmx/SavePurpose",
        dataType: "text",
        async: false,
        data: JSON.stringify({ Vid: Vid, PurpId: PurId }),
        contentType: "application/json; charset=utf-8",
        success: function (data) {
            Success = true;
        },
        error: function (textStatus, errorThrown) {
            Success = false;
        }
    });
    //done after here
    return Success;
} 

You can only return the values from a synchronousfunction. Otherwise you will have to make a callback.

您只能从synchronous函数返回值。否则你将不得不制作一个callback.

So I just added async:false,to your ajax call

所以我刚刚添加async:false,到你的 ajax 调用中

Update:

更新：

jquery ajax calls are asynchronous by default. So success & error functions will be called when the ajax load is complete. But your return statement will be executed just after the ajax call is started.

jquery ajax 调用默认是异步的。所以在ajax加载完成后会调用success&error函数。但是您的 return 语句将在 ajax 调用开始后立即执行。

A better approach will be:

更好的方法是：

     // callbackfn is the pointer to any function that needs to be called
     function ChangePurpose(Vid, PurId, callbackfn) {
        var Success = false;
        $.ajax({
            type: "POST",
            url: "CHService.asmx/SavePurpose",
            dataType: "text",
            data: JSON.stringify({ Vid: Vid, PurpId: PurId }),
            contentType: "application/json; charset=utf-8",
            success: function (data) {
                callbackfn(data)
            },
            error: function (textStatus, errorThrown) {
                callbackfn("Error getting the data")
            }
        });
     } 

     function Callback(data)
     {
        alert(data);
     }

and call the ajax as:

并将 ajax 称为：

 // Callback is the callback-function that needs to be called when asynchronous call is complete
 ChangePurpose(Vid, PurId, Callback);

回答by Tom Sarduy

Try to encapsulate the ajax call into a function and set the async option to false. Note that this option is deprecated since jQuery 1.8.

尝试将ajax调用封装成一个函数，并将async选项设置为false。请注意，此选项自 jQuery 1.8 起已弃用。

function foo() {
    var myajax = $.ajax({
        type: "POST",
        url: "CHService.asmx/SavePurpose",
        dataType: "text",
        data: JSON.stringify({ Vid: Vid, PurpId: PurId }),
        contentType: "application/json; charset=utf-8",
        async: false, //add this
    });
    return myajax.responseText;
}

You can do this also:

你也可以这样做：

$.ajax({
    type: "POST",
    url: "CHService.asmx/SavePurpose",
    dataType: "text",
    data: JSON.stringify({ Vid: Vid, PurpId: PurId }),
    contentType: "application/json; charset=utf-8",
    async: false, //add this
}).done(function ( data ) {
        Success = true;
}).fail(function ( data ) {
       Success = false;
});

You can read more about the jqXHR jQuery Object

您可以阅读有关jqXHR jQuery 对象的更多信息