Created
October 18, 2017 07:16
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Defer playground
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| package main | |
| import "sync" | |
| // deferはreturnの後だよ | |
| func A() string { | |
| str := "A" | |
| defer func() { | |
| str = "B" | |
| }() | |
| defer func() { | |
| str = "C" | |
| }() | |
| defer func() { | |
| str = "D" | |
| }() | |
| return str | |
| } | |
| // named returnだと戻り値を上書きできるよ | |
| func B() (str string) { | |
| str = "A" | |
| defer func() { | |
| str = "B" | |
| }() | |
| defer func() { | |
| str = "C" | |
| }() | |
| defer func() { | |
| str = "D" | |
| }() | |
| return str | |
| } | |
| func C() { | |
| str := "1" | |
| print(str) | |
| // その時の変数はキャプチャされるよ | |
| defer func() { | |
| print(str) | |
| }() | |
| str = "2" | |
| print(str) | |
| } | |
| func D() { | |
| str := "1" | |
| print(str) | |
| // 関数スコープで定義するとその時点の値が取れるよ | |
| defer func(s string) { | |
| print(s) | |
| }(str) | |
| str = "2" | |
| print(str) | |
| } | |
| // Goroutine | |
| func E() { | |
| var wg sync.WaitGroup | |
| for _, s := range []string{"A", "B", "C"} { | |
| wg.Add(1) | |
| go func(s string) { | |
| defer print(s) | |
| wg.Done() | |
| }(s) | |
| } | |
| println("Start") | |
| wg.Wait() | |
| println() | |
| println("End") | |
| } | |
| func main() { | |
| print(A()) | |
| println() | |
| print(B()) | |
| println() | |
| C() | |
| println() | |
| D() | |
| println() | |
| E() | |
| } |
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