Modern Chan Channel Close

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Close

Marks that no more values will be sent; values already buffered are still delivered.

Syntax

Close( )

Notes

• It is not a destructor and not a free: it is a broadcast. Every blocked receiver wakes, and every later Receive drains the buffer and then answers FALSE.
• Closing twice raises, and so does any send after it. Closing is a statement of fact that only the sending side may make, and making it twice -- or sending afterwards -- means two parties disagree about who owns the producer role.
• The channel's destructor does not close, because a scope that stopped holding a reference has not said that no more values are coming.
• Buffered values survive: a closed channel is drained before it reports closure.

Examples

#import "std/tasks"
using tasks

dim ch as Channel( of int32 ) = Channel( of int32 )( 4 )

dim as int32 v = 1
ch.Send( v )
ch.Close( )

print ch.IsClosed( )         '' true

'' The buffered value is still delivered -- closing does not discard
dim as int32 got
print ch.Receive( got )      '' true
print got                    '' 1
print ch.Receive( got )      '' false -- now it is drained

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Library: Goroutines and Channels
Category: Goroutines and Channels
Documented under: Members