Params with knockout component using instance

Question

I would like to send in params to an "instance" (singleton) of my knockout component using requirejs. The knockout help only shows examples of non instance parameter passing.

i have the following code which uses the instance and works correctly.

 //module declaration
 function unapAppointments()
{
      rest of code here.
}
 return {
        viewModel: {
            instance: new unapAppointments()
        },
        template: unapp,

    };

What i would like to do is something like the below passing in PARAMS from the component. This however obviously does not work.

 //module declaration
     function unapAppointments(PARAMS)
    {
          use PARAMS
    }
 return {
        viewModel: {
            instance: new unapAppointments(PARAMS)
        },
        template: unapp,

    };

Thanks

Answer 1

Returning a new instance depending on params contradicts the use of a shared instance viewmodel. This is exactly like using the viewmodel as constructor (accepting params) approach.

If you want to create a single instance, modify its internals depending on params each time before the binding is applied, you can use the createViewModel factory:

define(['knockout', 'text!./unapp.html'], function(ko, unapp) {

    function unapAppointments() {
        // rest of code here.
    }

    var mySingleton = new unapAppointments();

    function unapAppointmentsFactory(params, componentInfo) {
        // modify mySingleton using params
        return mySingleton;
    }

    return {
        viewModel: {
            createViewModel: unapAppointmentsFactory
        },
        template: unapp,
    };
});

But using this approach is delicate. If there is multiple components in the page, the last one to be bound wins, its params will override all the others.