Formatters | Roland Leth

Since creating formatters is very expensive, it's a good idea to have a singleton for them. But what if you have a standard style throughout the app, except a couple of places? Encapsulate it in a Static struct and set the required settings before returning:

struct Utils {
  
  class var numberFormatter: NumberFormatter {
    struct Static {
      static let formatter = NumberFormatter()
    }
  	
    Static.formatter.maximumFractionDigits = 2
    Static.formatter.alwaysShowsDecimalSeparator = false
  		
    return Static.formatter
  }
  
}

Then in the places with a different style:

let x = Utils.numberFormatter
x.maximumFractionDigits = 3
x.alwaysShowsDecimalSeparator = true
print(x.maximumFractionDigits) // => 3
print(x.alwaysShowsDecimalSeparator) // => true

But throughout the app the "default" settings will be returned:

let y = Utils.numberFormatter
print(y.maximumFractionDigits) // => 2
print(y.alwaysShowsDecimalSeparator) // => false

Just be careful with this approach - if you allocate y between allocating and using x, you will get the default settings for both x and y:

let x = Utils.numberFormatter
x.maximumFractionDigits = 3
x.alwaysShowsDecimalSeparator = true
 
let y = Utils.numberFormatter
 
print(x.maximumFractionDigits) // => 2
print(x.alwaysShowsDecimalSeparator) // => false