computed properties with parameters

[Chris Conroy]

The documentation for computed properties is not clear on support for parameters: http://docs.ractivejs.org/0.8/computed-properties

In the example given, the first option under "Data context for computed properties" is to use a function in data that takes a parameter rather than a computed property. However, this then loses the dependency tracking of a computed property. When I try to add a parameter to a computed property, I get function not found errors.

I can easily reference the relevant properties from my template as parameters to a normal function to work around this, but this can be more verbose than necessary.

Is there any way to pass parameters from the template into a computed property?

[Chris Reeves]

Actually, dependency tracking still happens with expressions that call data functions. If the deps are not passed as args to the function, you just have to make sure that you pull values using ractive.get inside the function body. When said keypaths are updated, any expression calling a data function referencing them will recompute.

There's no way to pass parameters to a computation, because then it wouldn't have a single value.

Thanks, Chris

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[Chris Conroy]

Ping: any thoughts here?

[Donny Velazquez]

I have used this hack before to use arguments with computed properties.

computed: {
            IsActiveList: function () {
                return (function (viewType) {
                    return viewType == this.get("active_list") ? "active" : "";
                }).bind(this);
            }
        }

I call it like this in the view.

{{IsActiveList(0)}}