英文:
What's the point of creating one-way channels in Go
问题
在Go语言中，可以创建单向通道。这是一个非常方便的功能，可以限制在给定通道上可用的一组操作。然而，据我所见，这个特性只对函数的参数和变量的类型规范有用，而通过make创建单向通道对我来说看起来很奇怪。我已经阅读了这个问题，但它不是关于在Go中创建只读（或只写）通道的问题，而是关于一般用法的问题。所以，我的问题是关于下面这段代码的用例：
writeOnly := make(chan<- string)
readOnly := make(<-chan string)
英文:
In Go one can create one-way channels. It's a very convenient feature in case of one want to restrict a set of operations available on the given channel. However, as far as I can see, this feature is useful only for function's arguments and variable's type specification, while creating one-way channels via make looks strange for me. I've read this question, but it's not about creating read (or write)-only channels in Go, it's about usage in general. So, my question is about use cases of the next code:
writeOnly := make(chan<- string)
readOnly := make(<-chan string)
答案1
得分: 4
理论上，你可以使用只写通道（write only channels）进行单元测试，以确保你的代码不会向通道写入超过特定次数的内容。
类似这样的代码：http://play.golang.org/p/_TPtvBa1OQ
package main
import (
"fmt"
)
func MyCode(someChannel chan<- string) {
someChannel <- "test1"
fmt.Println("1")
someChannel <- "test2"
fmt.Println("2")
someChannel <- "test3"
fmt.Println("3")
}
func main() {
writeOnly := make(chan<- string, 2) // 确保代码只向通道写入2次
MyCode(writeOnly)
}
但这对于单元测试来说是相当愚蠢的技术。更好的方法是创建一个带缓冲的通道并检查其内容。
英文:
Theoretically you can use write only channels for unit testing to ensure for example that your code is not writing more than specific number of times to a channel.
Something like this: http://play.golang.org/p/_TPtvBa1OQ
package main
import (
"fmt"
)
func MyCode(someChannel chan<- string) {
someChannel <- "test1"
fmt.Println("1")
someChannel <- "test2"
fmt.Println("2")
someChannel <- "test3"
fmt.Println("3")
}
func main() {
writeOnly := make(chan<- string, 2) // Make sure the code is writing to channel jsut 2 times
MyCode(writeOnly)
}
But that would be pretty silly technique for unit testing. You're better to create a buffered channel and check its contents.
答案2
得分: 0
人们使用类型（尤其是在Go语言中）的主要原因之一是作为一种文档形式。能够显示一个通道是只读还是只写，可以帮助API的使用者更好地了解正在发生的事情。
英文:
One of the main reason that people use types (especially in Go) is as a form of documentation. Being able to show that a channel is read-only or write-only, can help the consumer of the API have a better idea of what is going on.
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