Go Once: Difference between revisions
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* [[Go_Language_Goroutines#Once|Goroutines | Synchronization]] | * [[Go_Language_Goroutines#Once|Goroutines | Synchronization]] | ||
=Overview= | =Overview= | ||
<code>Once</code> is a Go synchronization construct that is used when a piece of code must be executed only once. This is a useful idiom in initialization. | <code>Once</code> is a Go synchronization construct that is used when a piece of code must be executed only once. This is a useful idiom in initialization. Note that the code is executed synchronously, when it is executed: the invocation to <code>Once#Do()</code> executes in the same goroutine that makes the <code>Once#Do()</code> invocation. | ||
=Example= | |||
<syntaxhighlight lang='go'> | <syntaxhighlight lang='go'> | ||
var log Log | |||
var initLogOnce sync.Once | |||
... | ... | ||
func GetLog() { | |||
initLogOnce.Do(func() { | |||
log = ... // init the log | |||
}) | |||
return log // because the function passed to Do() executes synchronously, log will be initialized here. | |||
}() | } | ||
</syntaxhighlight> | </syntaxhighlight> | ||
=Methods= | =Methods= | ||
Revision as of 23:10, 16 January 2024
Internal
Overview
Once is a Go synchronization construct that is used when a piece of code must be executed only once. This is a useful idiom in initialization. Note that the code is executed synchronously, when it is executed: the invocation to Once#Do() executes in the same goroutine that makes the Once#Do() invocation.
Example
var log Log
var initLogOnce sync.Once
...
func GetLog() {
initLogOnce.Do(func() {
log = ... // init the log
})
return log // because the function passed to Do() executes synchronously, log will be initialized here.
}
Methods
Do()
The only argument of Do() is a function value, not a function invocation. Do() will use the function value to invoke the function, internally.
All invokers will block, except one, and they will be released after the one that does initialization finishes executing. The others will no execute.