Type annotations vs. initializers & numbers.

I’ve noticed that experienced Swift developers are more likely to use type annotations instead of initializers when working with numbers.

That means using

let width: Float = 4

instead of

let width = Float(4)

I thought it was a holdover from Obj-C where type annotations come first. However, today I dealt with a bug that makes it clear adding type annotations is superior.

let a: CGFloat = 3 / 10 // 0.3
let b = CGFloat(3 / 10) // 0.0

In b, the division is done with two integers. Int rounds down, so it gives you the CGFloat version of 0. Probably not what’s intended.

On the other hand, for a, the compiler smartly wraps both integers in CGFloat, which gives you the result you’re actually looking for.