淘汰赛:找出计算出哪些可观察到的triggered [英] Knockout : find out which observable triggerred computed

问题描述

我有一个带有多个可观察对象的对象.计算对象中是否有一种方法可以知道哪些可观察到的变化，从而知道哪个可观察对象激发了计算对象?

I have an object with multiple observables. Is there a way in a computed to know which observable changes, therefore which observable fired the computed?

预先感谢您 马修

推荐答案

我没有详细说明要实现的目标，希望能对您有所帮助.

Without details of exactly what you are trying to achieve, I'll post this in the hope it might help.

跟踪更改的一种简单方法是在要跟踪的可观察对象上使用.subscribe方法.每次更新可观察对象时，就会触发此方法.

A simple way to track changes is to use the .subscribe method on an observable you want to track. Each time the observable gets updated, this method will fire.

self.myValue = ko.observable('initial value');

self.myValue.subscribe(function (item) {
    alert('myValue has changed to: ' + item);
});

传递给订阅函数的item是可选的，因此您可以根据需要使用新值.

The item passed in to the subscribe function is optional, so you can use the new value if required.

这是在计算中使用它的一个简单示例:

Here's a simple example of it in use with a computed:

JS:

var viewModel = function () {
    var self = this;
    self.firstName = ko.observable('Mod');
    self.lastName = ko.observable('dinu');

    self.valueChanged = ko.observable('');

    self.fullName = ko.computed(function () {
        var val = '';
        if (self.valueChanged() !== '') {
            val = ' (' + self.valueChanged() + ' Changed)';
        }

        return self.firstName() + ' ' + self.lastName() + val;
    });

    self.firstName.subscribe(function () {
        self.valueChanged('First Name');
    });

    self.lastName.subscribe(function () {
        self.valueChanged('Last Name');
    });
};

ko.applyBindings(new viewModel());

HTML:

<div>
    <label for="fname">First Name:</label>
    <input id="fname" data-bind="value: firstName" />
</div>
<div>
    <label for="lname">Last Name:</label>
    <input id="lname" data-bind="value: lastName" />
</div>
<hr />
<div>Hello <span data-bind="text: fullName"></span></div>
<hr />
<div>Value Changed: <span data-bind="text: valueChanged"></span></div>

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