Question

95

Binding a visible parameter to an 'or' statement in Knockout

rated 0 times [ 100] [ 5] / answers: 1 / hits: 22436 / 13 Years ago, tue, january 10, 2012, 12:00:00

I would like to bind a visible property to be true when one of two conditions are true. Something like the following

 <tr data-bind=visible: active || $parent.displayDeactive>....</tr>

My code works when I do one or the other bindings but not when I put the || in there. I haven't found any documentation that says I can put any logic in this binding, but if I can't do it directly what is the est way to do it since I am binding a property of a template and one object of the $parent viewmodel.

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dequant

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4 Years ago

answered 13 Years ago domeniccolti · Accepted Answer

If you are using the value of an observable in an expression then you need to reference them as a function. So, if active and displayDeactive are observables you would do:

data-bind=visible: active() || $parent.displayDeactive()

There are a few ways to move it to the view model, you could:

create a computed observable on the child (function would need to be able to reference the parent)

create a function on the parent that takes in the child and returns your value (bindings are executed in a computed observable, so it will fire again when any observable that it accesses changes)

create a function on the child that takes in the parent and returns the value (same note as above)

Sample of logic in the binding and using a function on the parent here: http://jsfiddle.net/rniemeyer/f6ZgH/