"Swift" Learning Notes (vi)--functions

This is the basic function of a programming language, and any language has the concept of function, which is a separate block of code that accomplishes a particular task.

How the function is created:

1. Create a function without parameter return value (virtually all functions have a return value, this function returns void, which is an empty tuple)

Func TestFunc () {    }

2. Create a function with a return value

Func TestFunc (), string{    return "Hello"}

3. Create a function with parameters and return values

Func TestFunc (name:string), string{    return "Hello" +name}

4. Create a function with multiple parameters and multiple return values

Func TestFunc (Name:string,age:int)-(myname:string,myage:int) {    return (name,age)}

5. Create a function with a parameter name

Func testFunc (MyName name:string,myage age:int) (myname:string,myage:int) {    return (name,age)}

PS: Call

TestFunc (MyName:" Xiao Wang ", MyAge:)

6, the 5th in another way, is the external parameter name and local variable name is the same time.

Func TestFunc (#name: String, #age: Int) (myname:string,myage:int) {    return (name,age)}testfunc (name: "Xiao Wang", age : 18)

7. Create a function with a default value parameter

Func TestFunc (#name: String,age:int = ten) (myname:string,myage:int) {    return (name,age)}testfunc (name: "Xiao Wang", AGE:18)

PS: Parameters with default values either do not specify an external parameter name (Swift will specify one by default is equivalent to a # number) or must be specified, cannot use the # number

8. Create a variable parameter function

Func allnums (nums:double ...), double{    var totalnum:double = 0 for    num in nums{        totalnum + = num    }
   return Totalnum}allnums (a)

9, function parameters are constants, can not be modified OH

For example:

Func error (A:int) {    A = 2    this will cause an error: Cannot assign to ' let ' value ' a '}

That can be created to modify. Of course. Add the var keyword.

Func error (Var a:int) {    a = 2}error (3)

10, the function parameter is the value of the transfer, that there is no way to make it a reference to pass it, that is, the parameters have been modified by the function, the external value of the function has changed

Func yy (inout a:int,inout b:int) {    var c = a    a = b    b = A}yy (&10, &20)

But this is wrong and what is wrong. That is, when the function is called, the incoming literal is changed. So to pass in the variable

var a = 10,b=20yy (&a, &b)

Big Brain storm: The function actually has the type, it also can be used as the parameter, the type.

For example:

Func yy (inout A:int,inout B:int)

This function, whose type is (Int,int), is ().

It can and int double this kind of use OH. ----'s so powerful.

Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.

"Swift" Learning Notes (vi)--functions