Question

我使用cordova的{{3}}插件和基于主干的应用程序。

我的Backbone.View有一个名为saveReport的方法。然后我有一个Backbone.Model，它有一个名为savePic的函数。这就是myView.saveReport的样子：

saveReport:function(){
    var promise = $.Deferred();
    promise.resolve();
    var that = this;
    promise.then(function(){
      var savePicPromise = $.Deferred();
      savePicPromise.resolve();
      for(var i=1; i< that.miniatureViews.length; ++i){
        savePicPromise = savePicPromise.then(function(){
          return that.miniatureViews[i].pictureModel.savePic();
        });
      }
      return savePicPromise;
    }).then(function(){
       // here I do all other things
       // ...
       // ...
    }); // promise chain.

myModel.savePic看起来像这样：

savePic: function(){
      var url = this.urlRoot;
      var options = new FileUploadOptions();
      options.fileKey="image";
      options.fileName=this.imgURI.substr(this.imgURI.lastIndexOf('/')+1);
      options.mimeType="image/jpeg";

      var ft = new FileTransfer();
      var myResponse; // to be set by callbacks.

      var that = this;
      this.savePromise = $.Deferred; // this should put a promise object into the model itself. 

      ft.upload(this.imgURI,
        encodeURI(url),
        function(r){
          that.savedURL = r.response; // this is the URL that the APi responds to us.
          that.savePromise.resolve();
        },
        function(e){
          console.error(e);
          window.analytics.trackEvent('ERROR', 'savingPic',e.code);
          that.savePromise.fail();
        },
        options);

      return this.savePromise;
    },

我还对代码进行了一些更改，并尝试使用其他两种模型的方法进行此配置：

ft.upload(this.imgURI,
        encodeURI(url),
        this.resolveSavePromise,
        this.failedSavePromise,
        options);

有两个功能：

resolveSavePromise: function(r){
      this.savedURL = r.response; // this is the URL that the APi responds to us.
      this.savePromise.resolve();
    },
    failedSavePromise: function(e){
      console.error(e);
      window.analytics.trackEvent('ERROR', 'savingPic',e.code);
      this.savePromise.fail();
    },

注意：在第二个选项中，我不会在savePic方法中返回任何内容。

问题是在saveReport方法的for循环中，存储在pictureModel中的promise实际上并不是一个承诺，或者至少表现得很奇怪。我在this.savePromise.resolve()：that.savePromise.resolve is not a function. (In 'that.savePromise.resolve()', 'that.savePromise.resolve' is undefined)"

这一行上收到错误

有没有更好的方法让插件的upload功能与promises很好地协同工作？

谢谢

Answer 1

您忘记创建延期。你刚刚做了

this.savePromise = $.Deferred;

虽然你真的想要

this.savePromise = new $.Deferred; // or
this.savePromise = new $.Deferred(); // or
this.savePromise = $.Deferred();

$.Deferred工厂确实没有.resolve方法。

顺便说一下，您想要return this.savePromise.promise()而不是延迟对象。

如何从cordova-plugin-file-transfer上传函数返回一个承诺

1 个答案: