What is the `?` is or the `:` at the equation when coding in Swift

Question

I have ran into a line of code in the infamous SevenSwitch class.

Here is the line...

backgroundView.layer.cornerRadius = self.isRounded ? frame.siz         


        

Answer 1

The ? and : are ternary operators. They are just shorthand for if statements.

An english translation of var a = b ? c : d where b is a boolean is set a equal to c if b is true, and to d if b is false.

So, for example,

backgroundView.layer.cornerRadius = self.isRounded ? frame.size.height * 0.4 : 2

can be translated into

if(self.isRounded){
    backgroundView.layer.cornerRadius = frame.size.height * 0.4
}
else{
    backgroundView.layer.cornerRadius = 2
}