In swift use of get and set is not compulsory and if use of "in" in closure is also not compulsory then how to differentiate a closure and computed property?

Like in below example greet is a closure or computed property?

var greet = {
  return 4 3
}

greet()

CodePudding user response：

greet is a closure. A computed property is

var greet : Int {
  return 4 3
}

And "in" in closure is also not compulsory if a parameter is passed (by the way the return keyword is not compulsory)

var greet = { x in
  4 x
}

greet(4)

unless you use the shorthand syntax

var greet = {
   4 $0
}

greet(4)

CodePudding user response：

You use the keyword in when you need to pass a parameter.

There are also differences between functions and computed properties: if you use the symbol =, you are equalling your variable to a function, so you need to call greet().

If instead = you use :, you have a computed property, call greet.

Here's a list of different cases:

        // greet is a function, you need to call greet()
        var greet = {
          return 4   3
        }
        print(greet()) // 7

        // greet2 is a computed property, you need to call greet2
        var greet2: Int {
            return 4   3
        }
        print(greet2) // 7

        // greet3 is a function that receives one parameter, you need to call greet3(someInt)
        var greet3 = { (parameter: Int) -> Int in
          return 4   parameter
        }
        print(greet3(4)) // 8

        // greet4 is like greet3, but the type is declared outside
        var greet4: (Int)->Int = { parameter in
            return 4   parameter
        }
        print(greet4(5)) // 9

        // greet5 is like greet4, where you define the function later
        var greet5: (Int) -> Int
        greet5 = { parameter in
            return 4   parameter
        }
        print(greet5(6)) // 10