cordovaSQLite无法正常工作，错误：undefined不是对象（评估'n.transaction'） [英] cordovaSQLite not working, Error: undefined is not an object (evaluating 'n.transaction')

问题描述

这是我确定导致问题的代码部分：

This is the section of code I have pinpointed to be causing the problem:

angular.module('starter.controllers', []).controller('StudentsCtrl', function ($scope, $cordovaSQLite) {

  var query = "SELECT id, student_id, username FROM students";
  var users = [];

  $cordovaSQLite.execute(db, query).then(function (data) {
    $.each(data, function(i, item) {
      users.push(item);
    });
  });

  $scope.users = users;
});

我已经包含了 $ cordovaSQLite 上班。以上代码位于 www / js / controllers.js 内，作为默认Ionic选项卡项目的一部分。 $ cordovaSQLite 在 www / js / app.js 内工作正常，并且在<$ c的另一部分也可以正常工作$ c> www / js / controllers.js ，但上面的代码部分给我发回了这个错误：

I have included the necessary files for $cordovaSQLite to work. The above code is inside of www/js/controllers.js, as part of the default Ionic tabbed project. $cordovaSQLite works fine inside of www/js/app.js and also works fine in another section of www/js/controllers.js, but the above section of code returns me this error:

0     610246   error    Error: undefined is not an object (evaluating 'n.transaction')

更新：此功能中似乎 $ cordovaSQLite 等于 undefined ，但我不确定为什么会发生这种情况。

Update: It appears that $cordovaSQLite is equal to undefined here in this function, but I'm not really sure why this is happening.

推荐答案

您的代码在Cordova deviceready事件被触发之前运行。在使用任何设备功能（如插件）之前，您需要等待它。在Ionic中，如果你在控制器中使用$ ionicPlatform，你可以这样做：

Your code is running before the Cordova deviceready event has fired. You need to wait for it before using any device functions, like plugins. In Ionic, if you use $ionicPlatform in your controller, you can do:

$ ionicPlatform.ready（function（）{

作为一种包装需要等待的代码的方法。试试这个：

as a way to wrap code that needs to wait for it. Try this:

angular.module('starter.controllers', []).controller('StudentsCtrl,$ionicPlatform', function ($scope, $cordovaSQLite) {

  $ionicPlatform.ready(function() {
    var query = "SELECT id, student_id, username FROM students";
    var users = [];

    $cordovaSQLite.execute(db, query).then(function (data) {
      $.each(data, function(i, item) {
        users.push(item);
      });
    });

    $scope.users = users;
    
   });
  
});

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