无法在Angular 2 Inside Callback中设置类级别变量

时间:2017-01-11 20:18:31

标签: angular ecmascript-6

我确定我失踪了一些小事,我会第一个告诉你我没有Angular或ES6专家。我有以下代码集:

getScanner(){
    var that = this;
    cordova.plugins.barcodeScanner.scan(
       function (result) {
            console.log("OBJ "+result);

            that.data = result;

            //THIS IS DEFINED
            console.log("That data first is "+that.data);

             alert("We got a barcode\n" +
                     "Result: " + result.text + "\n" +
                     "Format: " + result.format + "\n" +
                     "Cancelled: " + result.cancelled);              
        }, 
        function (error) {
            alert("Scanning failed: " + error);
        }
    );

    //THIS IS UNDEFINED
    console.log("That data is finally "+that.data);

}

正如您在上面看到的那样,当我第一次在回调中设置that.data时,它会很好地打印到控制台。然后,一旦我到达Cordova电话之外的console.log,它就会失去参考。我做错了什么?

1 个答案:

答案 0 :(得分:5)

cordova.plugins.barcodeScanner.scan调用是异步的,因此在调用成功回调之后才会定义that.data

如果您查看控制台,您应该注意到"That data is finally"消息在 "That data first is"消息之前已记录