Go Language Grammar Summary

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

Recently looked at Golang, the grammar of Go language summed up a bit, make a quick reference

Data type

• var varName type,,,,,, var var1,var2… type var varName type = Value var varName1,varName2 type = Value1,Value2 var varName1,varName2=Value1,Value2 varName1,varName2:=Value1,Value2 define the data type.

• Declares that the variable that is not being used will be wrong at compile times.

• Constant definition: const varName = Value ,const varName type = Value

• stringString type values are immutable, but can be sliced, strings can be used + to connect

• iotaUsed to declare enum , which represents the self-added 1, initially 0

• var arrayName [N]typeUsed to declare an array, or use arrayName := [N]type{ v1,v2…} to declare

• Array declarations can be nested

• sliceUsed to represent slices, declaratively, var sliceName []type orsliceName := []type{v1,v2…}

• sliceSave a reference, not an entity

• sliceThere are some built-in functions to len get the length, cap get the maximum capacity, append append the data, and copy use to copy the data

• mapDeclared by var mapName map[keyType] valueType ormapName := make(map[keyType]valueType)

• mapCan be key : value initialized by

• makeMemory allocations for built-in types new for various types of memory allocations, new returns a pointer and make returns a value other than 0

Process Control

• ifStatements do not require parentheses and can be declared in an if statement, using if the conditions of the split statement

    if x:=function();x<10 {      fmt.Printf("x < 10,%d\n",x);  }else{      fmt.Print("x >= 10 ,%d\n",x);  }

• gotoStatement is similar to the C language, but jumps to a label that must be defined within the current function

• forStatements are similar to the C language, but break continue can be labeled and jump out of multiple loops.

• switchStatement break , if you want to forcibly execute the following case, you can use thefallthrough

Function

How to declare:

func funcName(input1 type1, input2 type2) (output1 type1, output2 type2)

• funcUsed to declare a function, the function is named funcName , followed by the input, the output data type.

• function can have multiple return values

• The function's value operation and pointer operations are similar to the C language, and the built-in types, string slice map directly using a similar pointer pass, do not use the fetch address character, but if you need to change slice the length, you need to take the address to wear the pointer.

• deferStatement is used to represent statements executed before a function is returned.

• type typeName func(input1 inputType1 , input2 inputType2 [, ...]) (result1 resultType1 [, ...])Used to declare a function type, mainly used in higher-order functions.

• importUsed to import packages, package to export packages, to use operators for package operations .

struct type

• How to declare:

    type Person struct {  name string  age int  }

• Anonymous, anonymous mode A contains all the types of B

    type Student struct {  Person  // 默认Person的所有字段  speciality string  }

• If there are fields in the anonymous type that conflict with itself, you can use anonymous type + . access

• Type of method declaration:

    func (r ReceiverType) funcName(parameters) (results)

• You can use: type typeName typeLiteral from a defined type, you can use a method to extend the functionality of the type after you have defined it.

• When you need to change the value inside a struct, you need to ReceiverType define it as a * pointer type, but you don't need it when you call it, and the go language automatically helps you do it.

• Method can be inherited and can be overloaded

Interface interface

• type InterfaceName interfaceUsed to defineinerface

• The interface type defines a set of methods that implement this interface if an object implements all the methods of an interface.

• Empty interface (interface{}) does not contain any method, because of this, all types are implemented with NULL interface

• A function takes interface{} as an argument, then he can accept any type of value as a parameter, and if a function returns interface{}, it can return any type of value

• value, ok = element.(T), here is value the value of the variable, ok is a bool type, element is a interface variable, T is the type of the assertion, if ok it is, it true element is indeed T of type.

• interfacecan be nested

Concurrent

• Using go keyword + to 函数名 implement concurrency

• Use channel to implement inter-thread communication, channel by make constructing, using <- to send and receive data.

• chanis channel the keyword, followed by the data type to ch <- v send the data, receive the v:=<-ch data, ch is the chan type.

    package main  import "fmt"  func sum(a []int, c chan int) {      total := 0      for _, v := range a {          total += v      }      c <- total  // send total to c  }  func main() {      a := []int{7, 2, 8, -9, 4, 0}      c := make(chan int)      go sum(a[:len(a)/2], c)      go sum(a[len(a)/2:], c)      x, y := <-c, <-c  // receive from c      fmt.Println(x, y, x + y)  }

• channelThe default is blocking, which allows for thread synchronization.

• ch := make(chan type, value)The value buffer length of the CHANNL can be set by setting a different channel when constructing it.

• closeUsed to closechannel

• Use select + case to select multiple channel

• Use select + case <- time.After(5 * time.Second) to set timeouts

• GoexitExits the currently executing goroutine, but the defer function also continues to invoke the

• GoschedWith the execution permission of the current goroutine, the scheduler schedules other waiting tasks to run and resumes execution from that location at some point.

• NumCPUReturns the number of CPU cores

• NumGoroutineReturns the total number of tasks that are holding ⾏ lines and queued

• GOMAXPROCSUsed to set the number of CPU cores that can be run