iOS Development Swift Chapter-(eight) functions (2)

iOS Development Swift Chapter-(eight) functions (2)

First, the function type

A function type is also a type of data that consists of a formal parameter type and a return value type, in the form

return value type (List of parameter types)

1 func sum (num1:int, num2:int), Int {2     return num1 + num23}

The function type of the SUM function is (int, int), int

1 func printline () 2 {3     println ("-----------")4 }

There are 4 ways to represent the function type of the PrintLine function

(1)void , void

(2)( ) ()

(3)Void-and ()

(4)() Void

Ii. defining variables using function types

You can use function types to define variables, and you can store this type of function in the future.

1 func sum (num1:int, num2:int), Int {2     return num1 + num23}4 var fn: (int, int), int = sum5 fn (ten//  back to

Because Swift has a type inference mechanism, it is also possible to write this

var fn = sum //FN After the type of the stored function must be (int, int), int

Third, function as parameter

As with other data types, functions can also function as arguments

1 func printresult (fn: (int, int),2{3     println ("  Operation result is:%d", fn (NUM1, num2))4 }

The FN parameter receives a function that must return an int, with 2 arguments of type int

1Func sum (num1:int, Num2:int)Int {2     returnNUM1 +num23 }4Func minus (Num1:int, num2:int)Int {5     returnNUM1-num26 }7Printresult (SUM, -,Ten)// -8Printresult (minus, -,Ten)//Ten

Iv. functions as return values

As with other data types, functions can also function as return values

1Func gotowork () {println ("go to work") }2Func Playfootball () {println ("play football") }3Func Howtodo (Day:int), () {4     ifDay <6 {5         returngotowork6}Else {7         returnPlayfootball8     }9 }Tenvar fn = Howtodo (7) One fn () A //play football

V. Function overloading

Function overloading: function name is the same, function type is different

The following 2 functions form an overload

(1) Function name: Sum, Function type: (int, int), int

1 func sum (num1:int, num2:int), Int {2     return num1 + num23}

(2) Function name: Sum, Function type: (int, int, int), int

1 func sum (num1:int, Num2:int, Num3:int), Int {2     return NUM1 + num2 +
   
     num3
    3 }
   

Six, nested functions

Global Functions : Functions defined in the global scope

nested functions : Functions defined in the body of a function

code example:

1Func Howtodo (Day:int), () {2Func gotowork () {println ("go to work") }3Func Playfootball () {println ("play football") }4     ifDay <6 {5         returngotowork6}Else{returnPlayfootball}7 }8var fn = Howtodo (5)9FN ()//go to workTenGotowork ()

Note : line 10th is the wrong wording, and the scope of the nested function is limited to the inner body of the function that defines the nested function