Building predicate (NSExpression) to determine icon color for Mapbox SymbolStyle layer

Question

I've recently started working with the Mapbox SDK on iOS and I've got some markers that I want to add to my map. Each marker represents an object that has several properties, among them: a type property (which backs to an enum) and a boolean property. I have a MGLSymbolStyleLayer defined and I've set most of the icon-related properties accordingly. Currently, I'm setting the icon color based solely on the "type" of the object like this:

let defaultColor = UIColor.blue
layer.iconColor = NSExpression(format: "MGL_MATCH(type, 'type1', %@, 'type2', %@, 'type3', %@, %@)", UIColor.orange, UIColor.purple, UIColor.yellow, defaultColor)

This is working well but now I need to add an additional piece of logic in the NSExpression to check the boolean property on each object and if it's true, then set the icon color to red; else, determine the icon color for each object based on it's type (using the logic defined above). So in a nutshell, I need an NSExpression that functions like this:

if feature.booleanProperty == true {
   // set icon color to red
} else {
   // set icon color based on the feature type
}

I've looked through the Mapbox Predicates and Expressions Reference doc but it's still not clear to me how I would implement this sort of conditional logic in an NSExpression. Can anyone tell me if this is possible to do and if so, how?

Answer 1

From what I tried:

NSExpression(format: "TERNARY(booleanProperty=YES, %@, MGL_MATCH(type, 'type1', %@, 'type2', %@, 'type3', %@, %@))", UIColor.red, UIColor.orange, UIColor.purple, UIColor.yellow, defaultColor)

SIDE NOTE: I tried only compositing ternary operators and evaluating on object, not this specific expression.