浅析Golang如何向已关闭的chan读写数据

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目录

• 1. 向已关闭的chan写
• 2. 向已关闭的chan读

1. 向已关闭的chan写

会直接panic，报 send to close channel错误

package main

func main() {
	// 创建缓冲区为4的字符串chan
	schoolChan := make(chan string, 4)
	// 放入3个值
	schoolChan <- "国防科大"
	schoolChan <- "北京大学"
	schoolChan <- "湖南大学"

	// 关闭chan
	close(schoolChan)

	// 尝试写数据，会panic: send to close channel
	schoolChan <- "中南大学"
}

2. 向已关闭的chan读

会返回2个值，若已关闭的chan中还存在值，第二个值为true，第一个值为对应的chan中的值，若已关闭的chan中不存在值，第二个值为false，第一个值为对应chan类型的零值

package main

import "fmt"

func main() {
	// 创建缓冲区为4的字符串chan
	schoolChan := make(chan string, 4)
	// 放入3个值
	schoolChan <- "国防科大"
	schoolChan <- "北京大学"
	schoolChan <- "湖南大学"

	// 关闭chan
	close(schoolChan)

	// 向已关闭的chan读
	if school, isEmpty := <-schoolChan; isEmpty {
		fmt.Println("school:", school)
	}

	// 向已关闭的chan读
	if school, isEmpty := <-schoolChan; isEmpty {
		fmt.Println("school:", school)
	}

	// 向已关闭的chan读
	if school, isEmpty := <-schoolChan; isEmpty {
		fmt.Println("school:", school)
	}

	// 向若chan不存在元素，则第二个参数的值为 false
	if school, isEmpty := <-schoolChan; isEmpty {
		fmt.Println("school:", school)
	}
}

使用for循环遍历chan，若chan未关闭则会堵塞等待chan放入元素，如chan关闭则取出chan内所有元素并终止循序

package main

import (
	"fmt"
)

func main() {
	// 创建缓冲区为4的字符串chan
	schoolChan := make(chan string, 4)
	// 放入3个值
	schoolChan <- "国防科大"
	schoolChan <- "北京大学"
	schoolChan <- "湖南大学"

	// 关闭chan
	close(schoolChan)

	// for循环遍历channel，会将已关闭的chan中缓冲区的数据取出完后终止循序
	for school := range schoolChan {
		fmt.Println("school:", school)
	}
}

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