Golang Foundation--elaborate defer

Defer anonymous function properties

• Execution is similar to destructors in other languages, followed by the execution of the function body in the order of invocation 相反顺序

  //执行顺序相反package mainimport "fmt"func main() {    fmt.Println("a")    defer fmt.Println("b")    defer fmt.Println("c")}/*输出acb*/

• Even if a function occurs 严重的错误 , it is similar to try...except

• Often used for resource cleanup, file closing, unlocking, and recording time

• Calls that support anonymous functions

• You can modify the result of a function calculation after return by using the anonymous function mate
  -If a variable in the function body is a parameter of an anonymous function when defer, the copy is obtained when the defer is defined, otherwise the address of a variable is referenced

  //支持匿名函数package mainimport "fmt"func main() {    for i := 0; i < 3; i++ {        defer func() { //函数体内的变量传递到defer匿名函数            fmt.Println(i) //此时引用的时变量i的地址        }()    }}/*输出333*/

• Go has no exception mechanism, but has panic/recover mode to handle errors

• Panic can be triggered from anywhere

  Panic error mechanism

  //panic 错误机制，遇到panic语句后，后面不会再执行package mainimport "fmt"func main() {    A()    B()    C()}func A() {    fmt.Println("func a")}func B() {    panic("Panic B")}func C() {    fmt.Println("func")}/*输出A()-->  func aB()---> panic: Panic B---------------    goroutine 1 [running]:    main.B()C()     C:/Users/faily/Desktop/workspace/src/defer1.go:17 +0x40    main.main()        C:/Users/faily/Desktop/workspace/src/defer1.go:8 +0x2c    exit status 2    exit status 1*/

• Defer, with recover and anonymous function handlers, a critical error (panic statement), a program error, continues execution, similar to the Python language, the try...except finally statement.

  //defer,recover机制，处理panic引发的机制package mainimport "fmt"func main() {    A()    B()    C()}func A() {    fmt.Println("func a")}func B() {    defer func() {                          //defer函数放在panic之前        if err := recover(); err != nil {   //注册recover函数(判断是否触发panic错误)，并判断            fmt.Println("Recover in B")     //如果程序出现panic，并且err不为nil(真实存在)        }     }()                                     //记住，defer的匿名函数大括号后要加上()                                    panic("Panic B")                        //跳过程序错误，继续后面的执行。}func C() {    fmt.Println("func C")}/*输出A()-->  func aB()-->  Recover in BC()-->  

  ~ ~ Leave a question, interested in a small partner welcome to answer

  Run the following code and parse the output

    package Mainimport "FMT" Func Main () {var fs = [4]func () {}//define a variable FS, type is an array, the type of the array element is funcfor I: = 0 ; I < 4; i++ {defer FMT. Println ("Defer i=", i) defer func () {fmt. PRINTLN ("Defer closure i=", I)} () Fs[i] = func () {fmt. Println ("Closure i=", i)}}for _, F: = Range fs {f ()}}