Trigger saveInto when dynamically changing value in dropdown

Question

Hello, 
 I have an interface that needs to show default value in dropdown for my users when some options are specified (see example below) 
 
 {
 a!DropdownField(
 label: "Toto dropdown",
 choiceLabels: {"1", "2", "3"},
 choiceValues: {1, 2, 3},
 value: ri!toto
 ),
 a!DropdownField(
 label: "Tutu dropdown",
 choiceLabels: {"4", "5", "6"},
 choiceValues: {1, 2, 3},
 value: ri!tutu
 ),
 a!DropdownField(
 label: "Foo dropdown",
 choiceLabels: {"Test", "Test2"},
 choiceValues: {140, 150},
 value: if(
 and(
 isnull(ri!foo), 
 a!isNotNullOrEmpty(ri!toto), 
 a!isNotNullOrEmpty(ri!tutu)
 ),
 if(
 and(ri!toto = 1, ri!tutu = 2), 
 140, 
 150
 ), 
 ri!foo
 ),
 saveInto: ri!foo
 )
 } 
 This interface is embedded in a form component, when i submit this form and the default value of the "Foo dropdown" hasn't been changed, since its saveInto aren't triggered, i can't retrieve the values in ri!foo. 
 I really need this default value system, how can i trigger those saveInto ?

Mike Schmitt · Answer

I'm unclear what you're trying to accomplish here. The apparent value of a dropdown at any given time hinges directly and exclusively on its " value " parameter (or the intersection of the current " value ", as well as the choice Label at the same position as the choice Value that matches the current value of the " value " parameter). This is useful because you can change it externally "from above", for lack of a better term. 
 But "triggering the saveinto" is just... not a thing. It suggests to me that you don't quite firmly understand yet the directionality of how saveInto s work. I'd suggest boiling it down to a simpler, one-interface example, and getting used to how it works. This can later be expanded back to a multi-layered interface structure where one calls the other with rule inputs, etc.