The meaning of <- in golang

In Golang, <- is a very important operator with multiple meanings and usages. In this article, we will explain several common uses of the <- operator and its meaning through examples.

1. Channel sending and receiving

Golang’s channel is an important component for realizing communication between coroutines. Use the <- operator to send and receive channels. Operation, the specific usage is as follows:

ch := make(chan int)

// 发送数据
ch <- 10

// 接收数据
x := &lt;- ch

The <- operator here has two different meanings:

• <- ch: Receive data from channel ch and assign it to variable x

• ch <- x: Change variable x Send to channel ch The direction of the arrow used in

  also indicates the direction of the data flow. The left side is the receiving operation and the right side is the sending operation.

2. Close the channel

The channel can also be closed using the close() function. Once the channel is closed, sending data again will cause panic. But you can continue to receive data. We can use the <- operator to detect whether the channel is closed. The value of

ch := make(chan int)
// 关闭通道
close(ch)
// 接收值和通道关闭状态
v, ok := <- ch

ok is false, which means the channel has been closed. If the channel's buffer is not empty, then <- will return the value in the buffer, otherwise a zero value of the corresponding type will be returned.

3. Used for non-blocking channel communication

<- It can also be used for non-blocking channel communication. When there is data to be received or sent in the channel, the corresponding operation will be performed, otherwise it will be returned immediately. This can be achieved by wrapping the operation in a select statement:

ch := make(chan int)
// 非阻塞接收，若通道为空，直接进入 default 分支
select {
case x := <- ch:
    fmt.Println(x)
default:
    fmt.Println("no data available")
}

// 非阻塞发送，若通道已满，直接进入 default 分支
select {
case ch <- 10:
    fmt.Println("data send")
default:
    fmt.Println("no receiver available")
}

In the above code, when the channel is empty, the first select statement will Directly execute the default branch; when the channel is full, the second select statement will also directly execute the default branch.

4. Used to prevent compiler warnings

In some cases, we may need to receive a value explicitly in the code, but we do not need to use this value. Using the <- operator achieves this purpose and also prevents the compiler from generating an "unused value" warning:

<- ch

This statement will be removed from channel chReceive a value and ignore it to achieve the purpose of "receiving but not using".

Through the above four examples, we can see the important role of the <- operator in Golang code. It is not only used for channel receive and send, but can also be used to prevent compiler warnings and non-blocking channel communication. Mastering these usages will help improve the readability and performance of our Golang code.

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