knockoutjs: can we create a dependentObservable function with a parameter?

Question

I have multiple input boxes that I want to hide/unhide based on a selection from user.

I can achieve this by having a separate dependentObservable for each input an

Answer 1

Taking the idea from @Arxisos even further, I came up with this.

self.showField = function (fieldName)
{
    return ko.dependentObservable(function () 
    {
        return this.selectedType() ? IsFeatureVisible(this, fieldName) : false;
    }, this)();
};

Answer 2

In Knockout, bindings are implemented internally using dependentObservables, so you can actually use a plain function in place of a dependentObservable in your bindings. The binding will run your function inside of a dependentObservable, so any observables that have their value accessed will create a dependency (your binding will fire again when it changes).

Here is a sample: http://jsfiddle.net/rniemeyer/2pB9Y/

html

type "one", "two", or "three": <input data-bind="value: text" /> 
<hr />
<ul data-bind="template: { name: 'itemTmpl', foreach: items }"></ul>

js

<script id="itemTmpl" type="text/html">
    <li data-bind="text: name, visible: viewModel.shouldThisBeVisible(name)"></li>
</script>

var viewModel = {
    text: ko.observable("one"),
    items: [{name: "one"}, {name: "two"}, {name: "three"}],
};

viewModel.shouldThisBeVisible = function(name) {
    return this.text() === name;
}.bind(viewModel);

ko.applyBindings(viewModel);

Answer 3

var someOtherViewModel = {
   showField: function(fieldName) {
       return ko.dependentObservable(function () {
           return viewModel.selectedType() ? IsFeatureVisible(viewModel, fieldName) : false;
       }, viewModel);
   }
};

You can create a function like the one above. The function returns a new dependent observable for the specific field name.

Now you can do:

<tr data-bind="visible: someOtherViewModel.showField('Field1')">

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Inform me if that code doesn't work - maybe I missed something. Then I'll edit this post.