v8.1.3
I want to bind to an output parameter’s child value, but I get a warning message 
This isn’t a “bug” exactly - I mean, we put that restriction in there on purpose.
That said, I’m not sure the purpose is valid any longer. Can you provide some motivation as to why you want to do this and why a binding directly on the output wouldn’t suffice?
I found I could get around this, as you said, by binding directly to the base object, however this meant first creating the base object as a custom prop first and binding that to the output. 2 steps instead of 1. Would be easier to just bind to the output object’s child keys directly.
What I used this for is to create the instancePosition object for the view used in a flex repeater in order to collapse/hide a row on certain conditions by setting the basis to 0px or 25px and grow and shrink to static 0. Hence I just wanted to bind to the instancePosition.basis key
Hey Carl, just adding my two cents - I would also like the ability to bind to individual output object members.
I’m using objects as a parameter organizational tool for some of my equipment template views (shown below). In my example, ‘cfg/io’ are user inputs while ‘calc’ contains calculated states. The goal is to expose some of these pre-calculated states to the parent view.
This mostly works fine with an expression structure binding on calc, but any expressions that reference other calc values get circular reference errors and don’t execute. I can work around it by just replicating the same expression, but for heavier expressions this wouldn’t be ideal.
Additionally, you lose the ability to apply a transform to specific values. I don’t have an example for this, but I’m sure you get the idea.