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iOS Swift Basics (retired) Variables and Constants Constants

Posted by Sean Higgins
Sean Higgins
296 Points

Is let always a constant?

what else could identify a constant?

1 Answer

Michael Hulet
Michael Hulet
47,912 Points
Michael Hulet
Michael Hulet
47,912 Points

Yes, let defines a constant in Swift. Take the following code for example:

let number = 4
println(number)
number = 7

The above code would throw a compiler error, because you're trying to reassign number to 7, but it's a constant, so you can't do that. The one seeming exception is when you're working with classes. Take an instance of UILabel, for example.

let label = UILabel(frame: CGRectMake(0, 0, 100, 100))
label.text = "This is totally legal"

You can set and reset properties of classes instantiated as a constant all you want, but you can't totally reassign the constant to another instance of a class, like this:

let label = UILabel(frame: CGRectMake(0, 0, 100, 100))
//This would throw a compiler error, because you're reassigning a constant
label = UILabel(frame: CGRectMake(100, 100, 0, 0))