Closed channel vs nil channel when writing

[clement auger]

hi,

I am looking for further details and explanations about the various behaviors

associated with closed Vs nil channels.

I already read

https://stackoverflow.com/questions/43616434/closed-channel-vs-nil-channel

and other publications such as

https://medium.com/justforfunc/why-are-there-nil-channels-in-go-9877cc0b2308 (for example)

They repeat the explanation of the behaviors the programmer will have to deal with,

however they don't really explain the internal, nor the reasons of the differences

found with this example https://play.golang.org/p/4LuZ32gzWbu when closing or niling the channel

I wonder under which case it is useful to panic on write, Vs branching to a default case within a select.

Said differently what is the advantage of a panic Vs a syntax like ok := mychan <- myval; if !ok { return "not wrote" }

This happened while reading at T.L. in https://groups.google.com/forum/#!topic/golang-nuts/lEKehHH7kZY

Yes, there are ways to handle the problem of uncertain number of senders, but there are no simple ways.

A mechanism must be designed to avoid any sender writing to a closed channel.

thanks for anyone able to provide some details.

[Albert Tedja]

No such thing as a 'nil channel'. You are merely setting a variable to nil, regardless what the previous content is.

It's just that Go allows you to receive from a nil variable if that variable's type is a channel, in which case it blocks forever.

[T L]

https://go101.org/article/channel.html

[Jake Montgomery]

On Monday, September 2, 2019 at 9:41:54 AM UTC-4, T L wrote:

https://go101.org/article/channel.html

That is a great, and pretty detailed article. For quick reference I like https://dave.cheney.net/2014/03/19/channel-axioms .

[clement auger]

The compiler will produce the same result using an uninitialized channel variable (ie nil chan);

btw, the spec admits that a "nil channel" is a valid concept, several references can be found within it.

You might as well quote the specification rather than rephrasing, it is way shorter and efficient.

https://golang.org/ref/spec#Send_statements

"A send on a nil channel blocks forever. "

[clement auger]

sorry i can t find the added value i m looking for within those two publications.

thanks for trying to help, it will be good pointers for future readers starting to learn go and reading those words.