Custom Operators in Swift


04 May 2020 . 2 min read       @gurjitpt

Swift provides a very useful feature which is to define your own custom operators. It is a very confusing topic in the beginning but it is very powerful to use. It increases our code readability and provides a very clear and concise way to write code.

You can declare custom operators by defining static type method inside an extension. First of all, you have to decide your operator type that is it prefix, infix or postfix.

Prefix Operators

You can declare prefix operator with prefix modifier before the func keyword.

extension String {
     static prefix func !! (name: String) -> String {
           return "Hello " + name
//will print Hello Gurjit

In the above example:

Infix Operators

Infix operators are different than prefix operators and postfix operators. In Infix operators we have to define its precedence and associativity.

We are not talking about precedence and associativity in this article but if you want an explanation for this topic please go-ahead to this link

infix operator ^^: MultiplicationPrecedence
extension Int {
      static func ^^ (num: Int, power: Int) -> Int {
           return Int(pow(Double(num), Double(power)))
print(5 ^^ 2)

In the above example,

Postfix Operators

You can declare postfix operator with postfix modifier before the func keyword.

extension Double {
       static postfix func % (percentage: Double) -> Double {
              return (Double(percentage) / 100)
//will print 0.3

In the above example:


As the examples show custom operators are very useful to reduce code duplication and provides a very clean way to write code.

It’s very handy to write custom operators to write robust code when working in teams, that code is understood by others.


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