Swift Style, 1st Edition

Balancing Literals and Types

Although the Swift compiler infers typing for literals like 2 and “Hello,” you will never cause an error or reduce safety by explicitly typing declarations. Consider the following examples:

var aDouble = 23 // no, terrible variable name
let aFloat = 23 as Float // not preferred
let anotherDouble: Double = 23 // yes
var anotherFloat: Float = 23 // yes

Casting needlessly distances types from variable and constant names. A type should describe a symbol, not the value that’s being stored in it, so keep the type name close to its symbol:

let freezingPoint: CGFloat = 32.0  // yes
let freezingPoint = 32.0 as CGFloat // no

Mix-and-match inferencing creates inconsistent code. ...