[2019.03.08] Go lang (Map, Defer, Panic, Recover)

Map

map[string]int 는 참조 타입이므로 make를 해줘야한다.

make(map[string]int)

package main

import "fmt"

func main() {

    grades := make(map[string]int)

    grades["math"] = 90

    grades["korean"] = 85

    grades["english"] = 80

    fmt.Println(grades)

    fmt.Println(grades["korean"])

    for class, grade := range grades {

        fmt.Println(class, " : ", grade)

    }

}

---

defer

= 함수가 어떤 방식으로 끝나든 일단 끝나면 한다. 

= 함수를 한번 감싸서 끝나는 시점에 호출함

package main

import "fmt"

func foo() {

    defer fmt.Println("call 2")

    defer fmt.Println("call 1")

    fmt.Println("call 0")

}

func main() {

    foo()

}

call 0

call 1

call 2

---

Panic

package main

func main() {

    for i := 0; i < 5; i++ {

        if i == 3 {

            panic("!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!")

        }

    }

}

panic: !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

goroutine 1 [running]:

main.main()

/Users/-/Desktop/Project/Workspace_Golang/golang14_panic/golang.go:6 +0x58

exit status 2

---

Recover

package main

import "fmt"

func cleanup() {

    r := recover()

    if r != nil {

        fmt.Println("Recover exist, there might be panic : ", r)

    }

}

func main() {

    defer cleanup()

    for i := 0; i < 5; i++ {

        if i == 3 {

            panic("!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!")

        }

    }

}

Recover exist, there might be panic : !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!