Golang的channel与defer使用注意事项

chan的危险

channelGogoroutinechannelgoroutinechannelgoroutinegoroutinechannelgoroutine

package ct

import (
	"fmt"
	"testing"
)

func Run(channel chan int) {
	defer func() {
		fmt.Printf("end ....\n")
	}()
lable:
	v, _ := <-channel
	if v == 0 {
		return
	} else {
		goto lable
	}
}

func TestChan3(t *testing.T) {
	var channel chan int = make(chan int, 10)
	for index := 0; index < 15; index++ {
		go Run(channel)
	}
	for index := 0; index < 10; index++ {
		channel <- 0
	}
}
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channel0goroutineforRungoroutineforgoroutineforRungoroutinegoroutine

chan有界，越界必阻

channelmakechannelchannelchannelgoroutinegoroutinechannel

package ct

import (
	"fmt"
	"testing"
)

func goSend(msgChan chan int) {
	for index := 0; index < 100; index++ {
		fmt.Printf("send: %v\n", index)
		msgChan <- index
	}
}

func goRevice(msgChan chan int) {
	v, _ := <-msgChan
	fmt.Printf("revice: %v\n", v)
}

func TestChan(t *testing.T) {
	msgChan := make(chan int, 1)
	go goRevice(msgChan)
	goSend(msgChan)
}
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这个代码的输出结果为：

send: 0
send: 1
revice: 0
send: 2
Tests timed out after 60000 ms
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channel1goRevicegoroutinechannelgoSendsend 00send 1channelgoSendgoRevicechannelrevice: 0goSend1goRevicechannel1goSendsend: 2Tests timed out

循环中使用defer

10deferpanicfordefer

import (
	"errors"
	"fmt"
	"testing"
	"time"
)

func CreateError() {
	panic(errors.New("error"))
}

func TestDefer(t *testing.T) {
	var msgs []string = make([]string, 3)
	msgs[0] = "wu"
	msgs[1] = "jiu"
	msgs[2] = "ye"
	for _, message := range msgs {
		defer func(msg string) {
			fmt.Printf("=====> do defer, by %s ...\n", msg)
			if err := recover(); err != nil {
				fmt.Println(err)
			}
		}(message)
		CreateError()
	}
}
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deferfortryfinallyforfor

deferdeferdefer

func TestDefer(t *testing.T) {
	var msgs []string = make([]string, 3)
	msgs[0] = "wu"
	msgs[1] = "jiu"
	msgs[2] = "ye"
	defer func() {
		fmt.Printf("end .....\n")
	}()
	defer func() {
		fmt.Printf("end2 ....\n")
	}()
	for _, message := range msgs {
		if message == "ye" {
			CreateError()
		}
	}
	defer func() {
		fmt.Printf("end3 ....\n")
	}()
}
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上面程序输出结果如下：

end2 ....
end ....
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