Golang中defer、閉包以及命名傳回值

defer 後面跟普通函數

package mainfunc main() {    run()}func run() {    name := "Paul"    defer sayHello(name)     name = "John"}func sayHello(name string) {    println("Hello " + name)}// Hello Paul 只是延緩執行，實參會按照正常順序傳入函數中

defer、return 和未命名的傳回值

package mainfunc main() {    name := run()    println("return: name = " + name) }func run() (string) {    name := "Paul"    defer sayHello(&name)    name = "John"    return name}func sayHello(name *string) {    *name = "George"    println("Hello " + *name)}//Hello John  雖然實參提前傳入，但是傳入的是一個指標，最後執行拿到的是經過修改過的值//Hello George//return: name = John  未命名傳回值，所以 defer 無法對返回的值進行操作的

defer、return 和命名的傳回值

package mainfunc main() {    name := run()    println("return: name = " + name) func run() (x string) {    name := "Paul"    x = name    defer sayHello(&x)     name = "John"    return name}func sayHello(name *string) {    println("Hello " + *name)    *name = "George"    println("Hello " + *name)}//Hello John//Hello George//return: name = George 因為使用命名傳回值，所 defer 裡面依然可以對 defer 進行操作

package mainfunc main() {    name := run()    println("return: name = " + name) func run() (x string) {    name := "Paul"    x = name    defer sayHello(x)    name = "John"    return name}func sayHello(name string) {    println("Hello " + name)    name = "George"    println("Hello " + name)}//Hello Paul  順延強制但是按照程式順序執行，傳入的實參為 Paul //Hello George 函數內修改對外面的值沒有影響//return: name = John 

defer 閉包函數

package mainfunc main() {    name := run()    println("return: name = " + name)}func run() (string) {    name := "Paul"    aFun := func() {        println("Hello " + name)        name = "George"        println("Hello " + name)    }    name = "John"    aFun()    return name}//Hello John 雖然閉包定義時，外部變數 name = "Paul", 但是其實只是記錄是一個指標，所以最後執行的時候 name = "John" //Hello George//return: name = George

package mainfunc main() {    name := run()    println("return: name = " + name)}func run() (x string) {    name := "Paul"    aFun := func() {        println("Hello " + x)        x = "George"        println("Hello " + x)    }    defer aFun()    name = "John"    return name}//Hello John //Hello George//return: name = George  defer 對傳回值進行了修改

package mainfunc main() {    name := run()    println("return: name = " + name)}func run() (x string) {    name := "Paul"    x = name    aFun := func(x string) {        println("Hello " + x)        x = "George"        println("Hello " + x)    }    defer aFun(x)    name = "John"    return name}//Hello Paul  實參按照順序拷貝傳入 x = "Paul"//Hello George //return: name = John  因為設定了形參所以閉包內的對應的變數只是在局部生效，不會影響外部變數