设置knockout.js可观察属性而无需订阅射击

Question

如何设置可观察属性而不对其进行任何订阅射击？

我有一个场景是页面加载，ajax调用是为了获取一些数据，数据是循环播放，然后将当前选定的项目设置为可观察。我希望能够在没有任何订阅的情况下设置这个observable，因为第一次设置这个observable被认为是它的初始状态，并且订阅不应该在初始状态下执行。

function PlanViewModel() { 
    var self = this; 

    self.plans = ko.observableArray(); 
    self.selectedItem = ko.observable(); 

    self.getAllPlans = function() { 
     $.ajax({ 
      url: "/Backoffice/Home/GetAllPlans", 
      type: "POST", 
      data: {}, 
      context: this, 
      success: function (result) { 
       var planList = this.plans; 
       // clear the plan list 
       planList.removeAll(); 
       $.each(result.plans, function() { 
        var planDetail = new PlanDetail(this, self); 
        if (this.IsSelected) { 
         self.selectedItem(planDetail); // how do I set this without the subscriptions firing? 
        } 
        planList.push(planDetail); 
       }); 
      }, 
      error: function (result) { 
       alert("An error occured getting plans."); 
      } 
     }); 
    } 

    self.selectedItem.subscribe(function (newItem) { 
     newItem.repositoryUpdateSelectedPlan(); 
    } .bind(self)); 
} 

Answer 1

谢谢，我沿着这条路线走了一段路，并对其进行了一些修改。 selectedItem observable必须在模型中定义，因为它用于绑定遍布整个地方，但我确实按照您的建议移动了订阅部分，而且工作效果很好。

function PlanViewModel() { 
    var self = this; 

    var selectedItemSubscription = null; 

    self.plans = ko.observableArray(); 
    self.selectedItem = ko.observable(); 

    self.getAllPlans = function() { 
     $.ajax({ 
      url: "/Backoffice/Home/GetAllPlans", 
      type: "POST", 
      data: {}, 
      context: this, 
      success: function (result) { 
       var planList = this.plans; 
       // clear the plan list 
       planList.removeAll(); 
       $.each(result.plans, function() { 
        var planDetail = new PlanDetail(this, self); 
        if (this.IsSelected) { 
         if (selectedItemSubscription != null) 
          selectedItemSubscription.dispose(); 

         self.selectedItem(planDetail); 
        } 
        planList.push(planDetail); 
       }); 

       selectedItemSubscription = self.selectedItem.subscribe(function (newItem) { 
        newItem.repositoryUpdateSelectedPlan(); 
       }.bind(self)); 
      }, 
      error: function (result) { 
       alert("An error occured getting plans."); 
      } 
     }); 
    } 
} 

Answer 2

你可以调整你的代码是这样的：

function PlanViewModel() { 
    var self = this; 

    self.plans = ko.observableArray(); 

    self.getAllPlans = function() { 
     $.ajax({ 
      // … 
      success: function (result) { 
       // … 
       $.each(result.plans, function() { 
        var planDetail = new PlanDetail(this, self); 
        if (this.IsSelected) { 
         self.selectedItem = ko.observable(planDetail); 
        } 
        planList.push(planDetail); 
       }); 
       if (self.selectedItem === undefined) { 
        self.selectedItem = ko.observable(); 
       } 
       self.selectedItem.subscribe(function (newItem) { 
        newItem.repositoryUpdateSelectedPlan(); 
       }.bind(self)); 
      }, 
      // … 
     }); 
    } 
} 

也就是说，只有启动所需的初始状态达到淘汰赛后。