class Sync::ConditionVariable

Overview

Suspend a fiber until notified.

AConditionVariable can be associated to anyLockable.

While oneLockable can be associated to multipleConditionVariable, one ConditionVariable can only be associated to a singleLockable (one-to-many relation).

Condition variables may only be preferred overWaitGroup orChannel(T) for specific scenarios that need towake a single fiber (signal) or all waiting fibers (broadcast). For example:

PreferChannel(T) to pass a local resource around over aMutex and ConditionVariable to protect a global resource, but sometimes you don't need to pass a value and only need to repeatedly signal one or multiple workers, inwhich case a condition variable might be useful.

PreferWaitGroup(T) if you need towait for a task to complete, or for a set ofworkers to be ready (specific lifetimes), but sometimes youwant to repeatedly or sporadically notify one or manyworkers that may be added or removed concurrently (unbounded lifetimes), inwhich case a condition variable might be useful.

Defined in:

sync/condition_variable.cr

Constructors

Instance Method Summary

Instance methods inherited from class Reference

==(other : self)
==(other : JSON::Any)
==(other : YAML::Any)
==(other) ==, dup dup, hash(hasher) hash, initialize initialize, inspect(io : IO) : Nil inspect, object_id : UInt64 object_id, pretty_print(pp) : Nil pretty_print, same?(other : Reference) : Bool
same?(other : Nil) same?, to_s(io : IO) : Nil to_s

Constructor methods inherited from class Reference

new new, unsafe_construct(address : Pointer, *args, **opts) : self unsafe_construct

Class methods inherited from class Reference

pre_initialize(address : Pointer) pre_initialize

Instance methods inherited from class Object

! : Bool !, !=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other) ===, =~(other) =~, as(type : Class) as, as?(type : Class) as?, class class, dup dup, hash(hasher)
hash hash, in?(collection : Object) : Bool
in?(*values : Object) : Bool in?, inspect(io : IO) : Nil
inspect : String inspect, is_a?(type : Class) : Bool is_a?, itself itself, nil? : Bool nil?, not_nil!(message)
not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, responds_to?(name : Symbol) : Bool responds_to?, tap(&) tap, to_json(io : IO) : Nil
to_json : String to_json, to_pretty_json(indent : String = " ") : String
to_pretty_json(io : IO, indent : String = " ") : Nil to_pretty_json, to_s(io : IO) : Nil
to_s : String to_s, to_yaml(io : IO) : Nil
to_yaml : String to_yaml, try(&) try, unsafe_as(type : T.class) forall T unsafe_as

Class methods inherited from class Object

from_json(string_or_io : String | IO, root : String)
from_json(string_or_io : String | IO) from_json, from_yaml(string_or_io : String | IO) from_yaml

Macros inherited from class Object

class_getter(*names, &block) class_getter, class_getter!(*names) class_getter!, class_getter?(*names, &block) class_getter?, class_property(*names, &block) class_property, class_property!(*names) class_property!, class_property?(*names, &block) class_property?, class_setter(*names) class_setter, def_clone def_clone, def_equals(*fields) def_equals, def_equals_and_hash(*fields) def_equals_and_hash, def_hash(*fields) def_hash, delegate(*methods, to object) delegate, forward_missing_to(delegate) forward_missing_to, getter(*names, &block) getter, getter!(*names) getter!, getter?(*names, &block) getter?, property(*names, &block) property, property!(*names) property!, property?(*names, &block) property?, setter(*names) setter

Constructor Detail

def self.new(lock : Lockable) #

Instance Method Detail

def broadcast : Nil #

Wakes up allwaiting fibers at once.

You canwake a singlewaiting fiberwith#signal.


def signal : Nil #

Wakes up onewaiting fiber.

ForRWLock andShared(T) all readers can acquire, thus multiple readers might bewoken at once, but only onewriter can acquire, thus only one readerwill bewoken at a time.

You canwake allwaiting fiberswith#broadcast.


def wait : Nil #

Blocks the calling fiber until the condition variable is signaled.

Thelock must be held upon calling. Releaseslock beforewaiting, so any other fiber can acquire the lockwhile the calling fiber iswaiting. The lock is re-acquired before returning.

ARWLock andShared(T) can be held in either read orwrite mode, the lockwill be reacquired in the same mode (read orwrite) before returning.

The calling fiberwill bewoken by#signal or#broadcast.