在戈朗恢复
就像 Java 、 C# 等语言中异常中的 try/catch 块一样。在 Go 语言中类似用于捕捉异常，recover 函数用于处理死机。这是一个内置函数，在 Go 语言的内置包中定义。这个功能的主要用途是重新控制惊慌失措的戈鲁丁。或者换句话说，它处理戈罗廷的恐慌行为。
语法:
func recover() interface{}
要点:
- 恢复函数总是在延迟函数内部调用，而不是在正常函数中调用。如果在正常函数内部或延迟函数外部调用恢复函数，则恢复函数不会停止如示例 1 所示的恐慌序列。因此，总是在延迟函数中调用 recover 函数，因为如果程序死机，延迟函数不会停止执行，所以 recover 函数通过简单地恢复 goroutine 的正常执行来停止死机序列，并检索传递给死机调用的错误值，如示例 2 所示。
- 只有在发生死机的同一个 goroutine 中调用，Recover 函数才有效。如果您在不同的 goroutine 中调用它，那么它将不会像示例 3 中所示的那样工作。
- 如果你想找到堆栈跟踪，那么使用在调试包下定义的打印堆栈函数。
例 1:
// Go program which illustrates
// the concept of recover
package main
import "fmt"
// This function is created to handle
// the panic occurs in entry function
// but it does not handle the panic
// occurred in the entry function
// because it called in the normal
// function
func handlepanic() {
if a := recover(); a != nil {
fmt.Println("RECOVER", a)
}
}
// Function
func entry(lang *string, aname *string) {
// Normal function
handlepanic()
// When the value of lang
// is nil it will panic
if lang == nil {
panic("Error: Language cannot be nil")
}
// When the value of aname
// is nil it will panic
if aname == nil {
panic("Error: Author name cannot be nil")
}
fmt.Printf("Author Language: %s \n Author Name: %s\n", *lang, *aname)
fmt.Printf("Return successfully from the entry function")
}
// Main function
func main() {
A_lang := "GO Language"
entry(&A_lang, nil)
fmt.Printf("Return successfully from the main function")
}
输出:
panic: Error: Author name cannot be nil
goroutine 1 [running]:
main.entry(0x41a788, 0x0)
/tmp/sandbox777592252/prog.go:35 +0x180
main.main()
/tmp/sandbox777592252/prog.go:46 +0x40
例 2:
// Go program which illustrates
// the concept of recover
package main
import (
"fmt"
)
// This function handles the panic
// occur in entry function
// with the help of the recover function
func handlepanic() {
if a := recover(); a != nil {
fmt.Println("RECOVER", a)
}
}
// Function
func entry(lang *string, aname *string) {
// Deferred function
defer handlepanic()
// When the value of lang
// is nil it will panic
if lang == nil {
panic("Error: Language cannot be nil")
}
// When the value of aname
// is nil it will panic
if aname == nil {
panic("Error: Author name cannot be nil")
}
fmt.Printf("Author Language: %s \n Author Name: %s\n", *lang, *aname)
fmt.Printf("Return successfully from the entry function")
}
// Main function
func main() {
A_lang := "GO Language"
entry(&A_lang, nil)
fmt.Printf("Return successfully from the main function")
}
输出:
RECOVER Error: Author name cannot be nil
Return successfully from the main function
例 3:
// Go program which illustrates
// recover in a goroutine
package main
import (
"fmt"
"time"
)
// For recovery
func handlepanic() {
if a := recover(); a != nil {
fmt.Println("RECOVER", a)
}
}
/* Here, this panic is not
handled by the recover
function because of the
recover function is not
called in the same
goroutine in which the
panic occurs */
// Function 1
func myfun1() {
defer handlepanic()
fmt.Println("Welcome to Function 1")
go myfun2()
time.Sleep(10 * time.Second)
}
// Function 2
func myfun2() {
fmt.Println("Welcome to Function 2")
panic("Panicked!!")
}
// Main function
func main() {
myfun1()
fmt.Println("Return successfully from the main function")
}
输出:
Welcome to Function 1
Welcome to Function 2
panic: Panicked!!
goroutine 6 [running]:
main.myfun2()
/tmp/sandbox157568972/prog.go:31 +0xa0
created by main.myfun1
/tmp/sandbox157568972/prog.go:24 +0xc0
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