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attr.classDynPred doesn't do what I expect
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I have a button, and sometimes I want to show it active. The button already has two classes applied, and when it is active I want to apply a third "active" class.

I expected attr.classDynPred to be for this purpose, but it doesn't add to the existing classes; it just sets or clears the entire class attribute.

So I am using attr.classDyn and I feed it a view that switches between two classes and three classes.

So why does attr.classDynPred exist? If I want to set or clear an entire attribute, can't I do that with attr.classDyn anyway, where clearing it means supplying an empty string for the value? Not quite the same as removing the attribute, but the same effect.

I'm trying to understand when I'd use attr.classDynPred.

.

You are right. As it stands now the only difference between attr.*Dyn and attr.*DynPred is that the latter removes the attribute when the predicate is false and the former only updates the value so conceptually they aren't quite the same but the effect in this case is. You might want to take a look at Attr.DynamicClass which, I suppose, does what you tought attr.classDynPred would. Its type is a different as it expects a View<'T> and a mapping 'T -> bool instead of a View<bool> which is a bit questionable in terms of the other parts of the API.

Maybe we should make attr.classDynPred work this way but that might be confusing as it would do a different thing than all the other ones.

By on 9/3/2015 2:52 AM ()

Attr.DynamicClass does exactly what I want. Thank you.

By on 9/3/2015 3:30 AM ()

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