使用Knockout-ES5时如何在自定义绑定中访问可观察对象 [英] How to access the observables in custom bindings when using Knockout-ES5

问题描述

如果模型属性为ko.observable()，则可以在自定义绑定中按以下方式访问这些属性.

If the model properties are ko.observable(), these can be accessed as below within the custom binding.

var observable = valueAccessor();

使用Knockout-ES5插件时，如何在自定义绑定中获得可观察的东西?检查下面的代码，并查找注释如何在此处获取propertyName?"

When using Knockout-ES5 plugin how to get hold of the observable within the custom binding? Check the code below and look for comment "How to get propertyName here?"

不使用Knockout-ES插件时，JS Fiddle 由 已更新小提琴，其模型已更改为使用Knockout-ES插件

ko.bindingHandlers.datepicker = {
    init: function(element, valueAccessor, allBindingsAccessor, viewModel) {
        //initialize datepicker with some optional options
        var options = allBindingsAccessor().datepickerOptions || {};
        $(element).datepicker(options);

        //handle the field changing
        ko.utils.registerEventHandler(element, "change", function () {
            var observable = valueAccessor();
            if (!ko.isObservable(observable)) {                
                console.log("Not Observable");
                //How to get propertyName here?
                //ko.getObservable(viewModel, 'propertyName');
                return;
            }
            observable($(element).datepicker("getDate"));
        });

        //handle disposal (if KO removes by the template binding)
        ko.utils.domNodeDisposal.addDisposeCallback(element, function() {
            $(element).datepicker("destroy");
        });

    },
    //update the control when the view model changes
    update: function(element, valueAccessor) {
        var value = ko.utils.unwrapObservable(valueAccessor()),
            current = $(element).datepicker("getDate");

        if (value - current !== 0) {
            $(element).datepicker("setDate", value);   
        }
    }
};

var viewModel = {
    myDate: new Date("11/01/2011"),
    setToCurrentDate: function() {
       this.myDate = new Date();   
    }
};

ko.track(viewModel);

ko.applyBindings(viewModel);

推荐答案

您可以将实际的observable传递给绑定:

You could pass the actual observable to the binding:

data-bind="datepicker: ko.getObservable($data, 'myDate') ..."

http://jsfiddle.net/xb6vR/1/

但这很丑.幸运的是，Knockout确实提供了一种从绑定中写入属性值的方法(未记录):

But that's ugly. Fortunately, Knockout does provide a way (undocumented) to write to a property value from a binding:

//handle the field changing
ko.utils.registerEventHandler(element, "change", function () {
    var writable = valueAccessor();
    if (!ko.isObservable(writable)) {                
        var propWriters = allBindingsAccessor()._ko_property_writers;
        if (propWriters && propWriters.datepicker) {
            writable = propWriters.datepicker;
        } else {
            return;
        }
    }
    writable($(element).datepicker("getDate"));
});

http://jsfiddle.net/xb6vR/3/

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