Go Language Primer "three": Learn go syntax with a piece of code

This is a creation in Article, where the information may have evolved or changed.

Write in front

The syntax of Golang is simple enough, but it changes a lot, just need to master the typical usage , do not need to know all the syntax sugar, so the code will not contain all possible grammatical forms.

Concurrency is a major theme of Golang, followed by a dedicated section that does not appear in this section.

There are also some "conventions":

• Visibility. There are private,protect,public in Java. Golang default is the first letter case to determine: the first uppercase variables, methods are public, all the scope is visible, the first letter lowercase is private, the file is visible.
• Simplicity. The package imported by import and the defined variables must be used, or the program will not compile. Therefore, the code var p ClassA is not a declaration definition, but contains initialization , in fact the memory has been allocated, which is easy to ignore.

The following code:

A normal Go language code, for Go language learning, the author of the 2016-11-29//declaration package, the package name and directory path consistent, to $GOPATH/SRC as the root, such as Src/math/add.go's package for math. In addition, if it is a portal (that is, contains the main function), the package name is main, which can be compiled into an executable file by Go build. Package main//Block Import Note://import must be used, not import, but not his import ("Fmt" "StrConv" "reflect")//block definition variable var (//INT type Includes Rune, Int8, Int16, Int32, Int64 and Byte, Uint8, UInt16, UInt32, UInt64.    Where Rune is Int32 's nickname, Byte is Uint8 's nickname. myInt int//float includes float32,float64 myfloat float32 mybool bool myString string)//block Declaration Const Const (Conststrin    g = "Hello World, Worlds")//Globally defined variable var globaldefinedvar interface{}//defines a struct (also a class, because Golang does not have the concept of a Class), object-oriented type person struct {    The member function of the name string age Int}//person, explicitly specifying p, the this pointer in Java, the function in Python the first parameter Selffunc (P *person) introducemyself () { Fmt. Println ("My name is" + p.name) fmt. Println (P.age)}func (P *person) shoot () {fmt. Println ("I can shoot, so I can play football.")} Defines an interface type Footballplayer interface {shoot ()}func main () {//////////////1. Variable definition////////////var localstring string localstring = ' string is a pair of double quotation marks (representing a single line) or an inverse quotation mark (representing multiple lines) that defines the '//////////////2.rune, byte array, string relationship Myrune: = ' i ' FMT. Println (Myrune)//rune converted to a string myrunestring:= string (myrune) fmt. Println (myrunestring)//rune converted to byte array bytes:=[]byte (myrunestring) fmt. Println (bytes)//interface{} type can be assigned any type, Java-like object type Globaldefinedvar = localstring Newvar: = ": = is a shorthand form of declaration and initialization, Automatically inferred type "FMT" by the system.  Println (Newvar)//////////////3. Array definition and initialization////////////myArray: = [3]int{1, 2, 3}//array definition, default initialized to 5 0 var MyArray2 [5]int FMT. Println (myArray2) fmt. Println (MyArray)//////////////4.slice////////////Myslice: = []int{1, 2, 3, 4}//create slice from array, note 1: How to use, from The first element is taken to the end, and [1:4] can be taken from the first to the fourth (not included). From Python (author note) MySlice2: = myarray[1:] Myslice=append (myslice,5,6,7)//////////////5.if,else block nothing special, mybool undefined The default is false, which executes else////////////if Mybool {fmt. Println ("if")} else {fmt. PrinTLN ("Else")}//////////////6.for loop////////////for index, Value: = Range Myslice {fmt. Printf ("index:%d,value:%d \ n", index, Value)} for (true) {FMT. Println ("can also be used this way, equivalent to while (true)")//Avoid infinite loops, direct break off break}//////////////7.map Create, delete and use, the range keyword makes With////////////MyMap: = Make (Map[string]int) mymap["a"] = 1 mymap["b"] = 2 mymap["C"] = 3 Delete (MyMap, "a") for key, value: = Range MyMap {fmt. Printf ("Key:%s,value:%d", key, Value)}//////////////8. Object-oriented//////////////object initialization in two ways, the first is to return a pointer, the second return    is the object. Note that new always returns the pointer jack: = new (person) Jack.name = "Jack" jack.age = "Amy": = person{"Amy", + Jack.introducem    Yself ()//proof is pointer (*jack). Introducemyself () amy.introducemyself ()//Throw exception Invalid indirect of Amy (type person) (*amy). Introducemyself () fmt. Println (reflect. TypeOf (Jack)) fmt. Println (reflect. TypeOf (Amy))//////////////9. Interface using//////Interface assignment, you can see that Jack's person class does not need to implement the interface can be implemented, only need to have the interface required functions.  var footballPlayer1 = Jack Footballplayer1.shoot ()//function call, can return multiple values myString = "Golang is awesome" myRet1, MyRet2 : = Receive2return2 (myString, myInt) fmt.    Println (MyRet1, MyRet2)//////////////10. Exception Handling//////////////error handling, calling a method of throwing exceptions malfunction ()//Two knowledge points:    1.recover collects exception information thrown by panic in the call stack//2.defer execution time is the execution of the defer function exits, similar to the last in Java, but does not need to enclose a large piece of code in curly braces, so that the level of code is reduced. Defer func () {if err: = Recover (); Err! = nil {fmt. PRINTLN (Err)}} ()//each defined variable and constant is to be used, no garbage is allowed, here is a print fmt.    Println (Mybool, Myfloat,conststring,myslice2)}func receive2return2 (param1 string, param2 int) (Ret1 string, Ret2 int) { Fmt. Println ("param1:" + param1) fmt. Println ("param2:" + StrConv. Itoa (param2)) return "returned" + param1, param2 + 1}func malfunction () {Panic ("some thing went wrong!")}