dispatch_once(3) BSD Library Functions Manual dispatch_once(3)NAME
dispatch_once — execute a block only once
SYNOPSIS
#include <dispatch/dispatch.h>
void
dispatch_once(dispatch_once_t *predicate, void (^block)(void));
void
dispatch_once_f(dispatch_once_t *predicate, void *context,
void (*function)(void *));
DESCRIPTION
The dispatch_once() function provides a simple and efficient mechanism to
run an initializer exactly once, similar to pthread_once(3). Well
designed code hides the use of lazy initialization. For example:
FILE *getlogfile(void)
{
static dispatch_once_t pred;
static FILE *logfile;
dispatch_once(&pred, ^{
logfile = fopen(MY_LOG_FILE, "a");
});
return logfile;
}
FUNDAMENTALS
The dispatch_once() function is a wrapper around dispatch_once_f().
SEE ALSOdispatch(3)Darwin May 1, 2009 Darwin
