Question

In my view model I have a IsMale value that has the value true or false.

In my UI I wish to bind it to the following radio buttons:

<label>Male
   <input type="radio" name="IsMale" value="true" data-bind="checked:IsMale"/>
</label> 
<label>Female
   <input type="radio" name="IsMale" value="false" data-bind="checked:IsMale"/>
</label>

The problem I think is checked expects a string “true” / “false”. So my question is, how can I get this 2-way binding w/ this UI and model?

Answer 1

One option is to use a writeable computed observable.

In this case, I think that a nice option is to make the writeable computed observable a “sub-observable” of your IsMale observable. Your view model would look like:

var ViewModel = function() {
   this.IsMale = ko.observable(true);

   this.IsMale.ForEditing = ko.computed({
        read: function() {
            return this.IsMale().toString();  
        },
        write: function(newValue) {
             this.IsMale(newValue === "true");
        },
        owner: this        
    });          
};

You would bind it in your UI like:

<label>Male
   <input type="radio" name="IsMale" value="true" data-bind="checked:IsMale.ForEditing"/>
</label> 
<label>Female
   <input type="radio" name="IsMale" value="false" data-bind="checked:IsMale.ForEditing"/>
</label>

Sample: http://jsfiddle.net/rniemeyer/Pjdse/