If the model properties are ko.observable(), these can be accessed as below within the custom binding.
var observable = valueAccessor();
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?"
JS Fiddle when not using Knockout-ES plugin courtesy of Another Look at Custom Bindings for KnockoutJS
Updated fiddle with model changed to use Knockout-ES plugin
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);
You could pass the actual observable to the binding:
http://jsfiddle.net/xb6vR/1/
But that's ugly. Fortunately, Knockout does provide a way (undocumented) to write to a property value from a binding:
http://jsfiddle.net/xb6vR/3/
As an addition to the answer of Michael Best, if you are using knockoutjs 3.0 together with the es5 plugin, it is not possible to access the observable with
allBindingsAccessor()._ko_property_writers;
However I figured out it is possible to access it with theko.getObservable
function. So it should look like this:And then
I ended up using combination of passing a propertyname and falling back to _ko_property_writers. JS Fiddle.
HTML
Javascript
Well, you could use the preprocess to put the getObservable and use it as normal inside the binding handler.