Is golang chan closed?

In golang, using chan for inter-thread communication is a very common operation. However, how to properly close a chan is an often asked question. In this article, we will explore the correct way to close chan in golang, as well as the reasons and precautions for closing chan.

1. Basic use of chan

In golang, communication between threads can be achieved using chan. A chan can be used to send and receive values. We can use make to create chan.

For example, we can create a chan that can send and receive int types like this:

ch := make(chan int)

The main operations of using chan include sending and take over. The sending operation is represented by the

For example, we can send a value to a chan like this:

ch

Then, we can receive this value from chan and store it Into a variable:

value :=

Note that sending and receiving operations will block the current thread until another thread performs the opposite operation. This is because send and receive operations are synchronous. If there is no other thread to perform the opposite operation, the current thread will remain blocked. This is also one of the main features of chan.

2. Closing of chan

In golang, if we perform an add operation on a chan and there are no receivers, the program will always block on this operation. In order to avoid this situation, we can use the method of closing chan.

In golang, you can use the close function to close a chan. For example, we can close a chan like this:

close(ch)

After closing the chan, we can continue to send values ​​to this chan, but these values ​​will not be successfully received. Also, the receive operation will no longer be blocked. If there is no value in chan that can be received, a zero value will be returned. For example, for chan of type int, 0 will be returned after closing.

3. Reasons for closing chan

In golang, closing a chan is usually for the following reasons:

(1) When we no longer need to When chan sends new data, we can close this chan to prevent subsequent sending operations from blocking the program.

(2) When we need to read some special values ​​to indicate that all the data in chan has been processed, we can close this chan. In this case, the receiver can continue to read data from chan until a zero value is read indicating that all values ​​have been processed.

(3) When we need to notify all receivers that an event has occurred, we can also close a chan.

In all the above cases, we need to turn off chan so that the program can handle it correctly. But it should be noted that turning off chan is not necessary. If we don't need to close a chan, we don't need to do it.

4. Notes

When closing chan, there are some things to pay attention to:

(1) After chan is closed, we cannot It sends data. If we try to send data to chan after closing it, the program will panic.

(2) After chan is closed, we can receive data from it. However, it should be noted that all data in the chan has been received, so the receive operation will return a zero value. If we try to receive data from chan after it has been closed, a zero value and a false value will be returned, indicating that the chan has been closed.

(3) When multiple threads access the same chan at the same time, you need to pay attention to the correct closing method. If we close a chan in one thread while another thread is still sending or receiving data to the chan, the program will panic.

5. Summary

In golang, chan is an important tool for inter-thread communication. We can use the make function to create chan and perform send and receive operations on chan. When we need to close a chan, we can use the close function to complete it. The main reasons for closing chan are to prevent the program from blocking, or to notify all receivers that a specific event has occurred. When closing chan, you need to pay attention to some details to ensure the correctness of the program.

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