Question

我正在使用knockout.js库，它有助于数据绑定。所以我一直得到错误，我的变量没有在我们的viewModel原型上的计算函数中定义。我知道这是因为计算出的函数正在改变＆＃34;这个＆＃34;到窗口，但我似乎无法弄清楚如何让它更改回根（viewModel）。我指的方法是＆＃34;消息＆＃34;在javascript中。话虽如此，如何将上下文更改回viewModel？

这是我的代码：

HTML

p#title.col-xs-12.bg-primary.text-center
  | Tic - Tac - Toe!
div.col-xs-3.bg-info
  div.bg-primary.controls
    span
      button.btn.btn-default(data-bind="click:StartMessage.bind($root)")
        | New Game
      p#message.lead(data-bind="text:Messages.bind($root)()")
table.bg-success(style="table-layout:fixed;")
  tr#row1
    td(data-bind="click:Messages.bind($root)")
    td &nbsp
    td &nbsp
  tr#row2
    td &nbsp 
    td &nbsp
    td &nbsp
  tr#row3
    td &nbsp 
    td &nbsp
    td &nbsp

JAVASCRIPT

var message = (function(){
  function Message(){
   this.main = ko.observable(true);
   this.welcome = "Welcome to Tic-Tac-Toe! This is a 2 player game. Click New Game to play!"
   this.turn = ", its your turn."
   this.win = ", you won!"
   this.draw = "It's a draw..."
  }
  return Message;
})()

var players = (function(){
  function Players(){
    this.player1 = ko.observable(true);
    this.player2 = ko.observable(false);
  }
  return Players;
})()

var aBox = (function(){
  function ABox(){
    this.symbol = ko.observable(" ")
  }

  return ABox;
})()

var viewModel = (function(){
  function ViewModel(){
    this.GameMessage = new message();
    this.thePlayers = new players();
    this.r1c1 = new aBox();
    this.r1c2 = new aBox();
    this.r1c3 = new aBox();
    this.r2c1 = new aBox();
    this.r2c2 = new aBox();
    this.r2c3 = new aBox();
    this.r3c1 = new aBox();
    this.r3c2 = new aBox();
    this.r3c3 = new aBox();

  }

/**************************************** 
 ************* Messages *****************
 ****************************************/ 

  ViewModel.prototype.StartMessage = function(){

     this.GameMessage.main(false)
  }

  ViewModel.prototype.Messages = ko.computed(function(){

    if(this.GameMessage.main()){
      return this.GameMessage.welcome;
    }
    else if(this.thePlayers.player1()){
      this.thePlayers.player1(false);
      this.thePlayers.player2(true);
      return "Player 1"+this.GameMessage.turn;

    }
    else if(this.thePlayers.player2())
      this.thePlayers.player1(true);
      this.thePlayers.player2(false);
      return "Player 2"+this.GameMessage.turn;
  },ViewModel)

  return ViewModel;
})()

ko.applyBindings(new viewModel())

我已尝试将上下文更改为＆＃34; viewModel＆＃34;如图所示，$ root，＆＃34; this。＆＃34;

如果您想知道该方法尝试完成的是什么，当单击“新消息”按钮时，它将触发要显示的消息。然后，如果单击<td>，它将在前一个地方显示不同的消息。

Answer 1

ko.computed函数包含allows to bind the computed function this to whichever object you specify的第二个参数。（在幕后它只使用apply）

因此，当您在原型中定义计算时，您只需将计算结果绑定到this，如下所示：

ViewModel.prototype.Messages = ko.computed(function(){
  // your function code
  }, this);

请记住，当您使用原型时，this会引用您感兴趣的对象实例。

viewModel使用knockout.js在原型上计算函数

1 个答案: