javascript - 成功回调未调用 webSQL 事务中的另一个函数

Question

请看下面的代码。我在 db.transaction 的 sucessCallBack 中调用了 setQuestion()，但收到此错误 Uncaught TypeError: this.setQuestions is not a function。

我的代码有什么问题吗？

game.module(
"game.scenes.scene"
)
.require(
    "game.assets",
    "game.entities.gameObject",
    "game.entities.backgroundObject",
    "game.entities.animeObject",
    "game.entities.starObject",
    "game.entities.buttonObject"
).body(function() {
  game.SceneScene1 = game.Scene.extend({
    loaded: function() {
         this.get_difficulty_level();
    },
    setQuestions: function() {
        //some code
     },
    get_difficulty_level: function(){
        var app_id = this.app_id;
        var user_id = this.user_id;
        db.transaction(function (transaction)
        {
            transaction.executeSql('SELECT * FROM User_report where app_id="'+app_id+'" and user_id="'+user_id+'" order by id desc limit 1;', [],
            function (transaction, result)
            {
                if (result.rows.length == 0)
                {
                   difficulty_level=2;
                }else{
                     difficulty_level = result.rows.item(0).difficulty;
                     console.log(result.rows.item(0));
                }
            });
          },this.errorHandler,this.successDiffi);
      },
      successDiffi: function(){
          this.setQuestions();
      },
});
});

Answer 1

发生这种情况是因为成功回调在您想象的范围之外的范围内被调用。要解决此问题，您可以尝试在回调中使用闭包:

game.module(
"game.scenes.scene"
)
.require(
    "game.assets",
    "game.entities.gameObject",
    "game.entities.backgroundObject",
    "game.entities.animeObject",
    "game.entities.starObject",
    "game.entities.buttonObject"
).body(function() {
  game.SceneScene1 = game.Scene.extend(
    new function () 
  {
    this.loaded =  function() {
         this.get_difficulty_level();
    };
    this.setQuestions= function() {
        //some code
     };
    this.get_difficulty_level= function(){
        var app_id = this.app_id;
        var user_id = this.user_id;
        db.transaction(function (transaction)
        {
            transaction.executeSql('SELECT * FROM User_report where app_id="'+app_id+'" and user_id="'+user_id+'" order by id desc limit 1;', [],
            function (transaction, result)
            {
                if (result.rows.length == 0)
                {
                   difficulty_level=2;
                }else{
                     difficulty_level = result.rows.item(0).difficulty;
                     console.log(result.rows.item(0));
                }
            });
          },this.errorHandler,this.successDiffi);
      };
      var _this = this;
      this.successDiffi= function(){
          _this.setQuestions();
      };
});
});