class Ractor::Selector

Ractor::Selector provides a functionality to wait multiple Ractor events. Ractor::Selector#wait is more lightweight than Ractor.select() because we don’t have to specify all target ractors for each wait time.

Ractor.select() uses Ractor::Selector internally to implement it.

Public Class Methods

Ractor::Selector.new(*ractors) click to toggle source

Creates a selector object.

If a ractors parameter is given, it is same as the following code.

selector = Ractor::Selector.new
ractors.each{|r| selector.add r}

# File ruby_3_3_0_preview3/ractor.rb, line 397
def self.new(*rs)
  selector = __builtin_cexpr! %q{
    ractor_selector_create(self);
  }
  rs.each{|r| selector.add(r) }
  selector
end

Public Instance Methods

add(ractor) click to toggle source

Registers a ractor as a taking target by the selector.

# File ruby_3_3_0_preview3/ractor.rb, line 410
def add r
  __builtin_ractor_selector_add r
end

clear click to toggle source

Deregisters all ractors.

# File ruby_3_3_0_preview3/ractor.rb, line 427
def clear
  __builtin_ractor_selector_clear
end

empty? click to toggle source

Returns true if the number of ractors in the waiting set at the current time is zero.

Note that even if #empty? returns false, the subsequent #wait may raise an exception because other ractors may close the target ractors.

# File ruby_3_3_0_preview3/ractor.rb, line 439
def empty?
  __builtin_ractor_selector_empty_p
end

remove(ractor) click to toggle source

Deregisters a ractor as a taking target by the selector.

# File ruby_3_3_0_preview3/ractor.rb, line 419
def remove r
  __builtin_ractor_selector_remove r
end

wait(receive: false, yield_value: yield_value, move: false) → [ractor or symbol, value] click to toggle source

Waits Ractor events. It is lighter than Ractor.select() for many ractors.

The simplest form is waiting for taking a value from one of registerred ractors like that.

selector = Ractor::Selector.new(r1, r2, r3)
r, v = selector.wait

On this case, when r1, r2 or r3 is ready to take (yielding a value), this method takes the value from the ready (yielded) ractor and returns [the yielded ractor, the taking value].

Note that if a take target ractor is closed, the ractor will be removed automatically.

If you also want to wait with receiving an object from other ractors, you can specify receive: true keyword like:

r, v = selector.wait receive: true

On this case, wait for taking from r1, r2 or r3 and waiting for receving a value from other ractors. If it successes the receiving, it returns an array object [:receive, the received value].

If you also want to wait with yielding a value, you can specify :yield_value like:

r, v = selector.wait yield_value: obj

On this case wait for taking from r1, r2, or r3 and waiting for taking yielding value (obj) by another ractor. If antoher ractor takes the value (obj), it returns an array object [:yield, nil].

You can specify a keyword parameter move: true like Ractor.yield(obj, move: true)

# File ruby_3_3_0_preview3/ractor.rb, line 481
def wait receive: false, yield_value: yield_unspecified = true, move: false
  __builtin_ractor_selector_wait receive, !yield_unspecified, yield_value, move
end