Default and Optional Arguments is one of the handy feature of Swift and was missing in Objective C.

With this feature we can have different arguments sequence for single method signature. This avoids forcing caller to pass values for all the arguments defined in the method signature.

Few examples:

Default Arguments:

func displayName(firstName: String = "John", middleName: String = "Smith", lastName: String = "Jr") -> Void {
    print("\(firstName)"+" "+"\(middleName)"+" "+"\(lastName)")
}

displayName() \\ -> John Smith Jr

displayName(middleName:"Trev") \\ -> John Trev Jr

displayName(middleName:"Trev", lastName: "Sr") \\ -> John Trev Sr

Optional Arguments


func displayName(firstName: String? = nil, middleName: String? = nil, lastName: String? = nil) -> Void {

    if let fName = firstName {
        print("\(fName)")
    }

    if let mName = middleName {
        print("\(mName)")
    }

    if let lName = lastName {
        print("\(lName)")
    }
}

displayName(firstName: "John", middleName: "Smith", lastName: "Jr")

Output:

John
Smith
Jr

displayName(firstName: "John", middleName: "Smith")

Output:

John
Smith

displayName(firstName: "John", lastName: "Jr")

Output:

John
Jr

displayName(middleName: "Smith", lastName: "Jr")

Output:

Smith
Jr

displayName(middleName: "Smith")

Output:

Smith