Validate entire form

[peacechen]

It would be handy if the form would indicate whether the entire form (all the child inputs) are valid. This controls whether the Submit button should be operable, for example. I've been trying to enumerate the child refs, checking the .valid field, but some inputs such as Picker don't have that field at all. Additionally, .valid isn't reliable because it can be true when the form first loads (uninitialized values set .valid true in the examples).

[matbalazsi]

+1