Question

在下面的代码中;为什么“self.ticketCollection.indexOf（t）”中的“self.Addticket-function always -1 ???

在page_load之后，我按下New（newTicket），然后按ADD（addTicket）。这工作正常，并且（“ny”，“ - 1”）的记录被添加到我的ticketCollection中。然后当我重复这个时，另外一个记录完全相同。调试器（FireBug）告诉我“self.ticketCollection.indexOf（t）”在两种情况下均为-1。为什么呢？

function Ticket(ticketname, cost) {
    var self = this;

    //alert("ikke implementer fullt ut ennå!");

    self.ticketname = ko.observable(ticketname);
    self.cost= ko.observable(cost);

} // end Ticket

//==============================================================

function ViewModel() {
var self = this;

//------ initiate ----------------------------------------------

// the product we want to view/edit
self.selectedTicket = ko.observable();

self.ticketCollection = ko.observableArray(
    [
        new Ticket("Bus", "$2"),
        new Ticket("Ferry", "$3"),
        new Ticket("Bicycle", "$1")
    ]);

// selected item from ticket list-view
self.listViewSelectedItem = ko.observable();

// push any changes in the list view to our main selectedTicket
self.listViewSelectedItem.subscribe(function (ticket) {
    if (ticket) {
        self.selectedTicket(ticket);
    }
}); // self.listViewSelectedItem.subscribe //


//---- NEW button pressed --------------------------------------
self.newTicket = function () {

        // create a new instance of a Ticket
        var t = new Ticket("ny", "-1");

        // set the selected Ticket to out new instance
        self.selectedTicket(t);

    }.bind(this);

//---- ADD to collection -----------------------------------------

self.addTicket = function () {
        //alert("ADD is pushed!");

        // get a reference to out currently selected product
        var t = self.selectedTicket();

        // ignore if null
        if (!t) { return; }

        // check to see that the ticket doesn\t already exist
        if (self.ticketCollection.indexOf(t) > -1) {
            return;
        }

        // add the product to the collection
        self.ticketCollection.push(t);

        // clear out the selected product
        self.selectedTicket(t);
        //self.listViewSelectedItem(t)

    };
} // end ViewModel

提前完成！

阿斯勒：）

Answer 1

仅仅因为你有两个包含完全相同值的Ticket个对象，并不意味着这两个对象是相等的。这就是indexOf每次返回-1的原因 - 因为ticketCollection可观察数组不包含您要检查的确切项目。这个SO问题很好地解释了JavaScript对象的平等性：How to determine equality for two JavaScript objects?

您应该检查indexOf中的任何项目是否与新ticketCollection和ticketName匹配，而不是使用数组上的cost。，来袭票。

我将添加一个我的意思的例子：

for(var i=0, len=self.ticketCollection().length; i < len; i++){
if ((t.ticketname() === ticketCollection()[i].ticketname()) && (t.cost() === ticketCollection()[i].cost())) {
    alert('Found the object in the observable array')
}

为什么indexOf没有用？

1 个答案: