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- .\" Copyright (c) 2008-2010 Apple Inc. All rights reserved.
- .Dd May 1, 2009
- .Dt dispatch_after 3
- .Os Darwin
- .Sh NAME
- .Nm dispatch_after
- .Nd schedule blocks for deferred execution
- .Sh SYNOPSIS
- .Fd #include <dispatch/dispatch.h>
- .Ft void
- .Fo dispatch_after
- .Fa "dispatch_time_t when" "dispatch_queue_t queue" "void (^block)(void)"
- .Fc
- .Ft void
- .Fo dispatch_after_f
- .Fa "dispatch_time_t when" "dispatch_queue_t queue" "void *context" "void (*function)(void *)"
- .Fc
- .Sh DESCRIPTION
- The
- .Fn dispatch_after
- function submits the
- .Fa block
- to the given
- .Fa queue
- at the time specified by the
- .Fa when
- parameter.
- The
- .Fa when
- parameter is a value created by
- .Fn dispatch_time
- or
- .Fn dispatch_walltime .
- Submission of the block may be delayed by the system in order to improve power consumption and system performance.
- The system applies a leeway (see
- .Xr dispatch_source_set_timer 3 )
- that is equal to one tenth of the interval between
- .Fa when
- and the time at which the function is called, with the leeway capped to at least one millisecond and at most one minute.
- .Pp
- For a more detailed description about submitting blocks to queues, see
- .Xr dispatch_async 3 .
- .Sh CAVEATS
- .Fn dispatch_after
- retains the passed queue.
- .Pp
- Specifying
- .Vt DISPATCH_TIME_NOW
- as the
- .Fa when
- parameter
- is supported, but is not as efficient as calling
- .Fn dispatch_async .
- .Pp
- The result of passing
- .Vt DISPATCH_TIME_FOREVER
- as the
- .Fa when
- parameter is undefined.
- .Pp
- .Sh FUNDAMENTALS
- The
- .Fn dispatch_after
- function is a wrapper around
- .Fn dispatch_after_f .
- .Sh SEE ALSO
- .Xr dispatch 3 ,
- .Xr dispatch_async 3 ,
- .Xr dispatch_time 3
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