iOS Functions in Swift Adding Power to Functions Returning Complex Values

What this does it mean? Cannot convert value of type '()' to expected argum

I've got the same code as Pasan, I belive that now Swift is another version and I don't know if smth changes...

Everything was running perfectly but when I assign the area function into the carpetCostHaving function, I have this error into the switch operator

case "tan": price = areaOfRoom * 2

Does anybody knows whats about that?

Can you provide more code ore more detail of the error