Ruby Ractor.select用法及代碼示例

select(*ractors, [yield_value:, move: false]) → [ractor or symbol, obj]

等待第一個 ractor 在其傳出端口中有內容，從該 ractor 讀取，並返回該 ractor 和接收到的對象。

r1 = Ractor.new {Ractor.yield 'from 1'}
r2 = Ractor.new {Ractor.yield 'from 2'}

r, obj = Ractor.select(r1, r2)

puts "received #{obj.inspect} from #{r.inspect}"
# Prints: received "from 1" from #<Ractor:#2 test.rb:1 running>

如果給定的 ractor 之一是當前的 ractor，並且它將被選中，則 r 將包含 :receive 符號而不是 ractor 對象。

r1 = Ractor.new(Ractor.current) do |main|
  main.send 'to main'
  Ractor.yield 'from 1'
end
r2 = Ractor.new do
  Ractor.yield 'from 2'
end

r, obj = Ractor.select(r1, r2, Ractor.current)
puts "received #{obj.inspect} from #{r.inspect}"
# Prints: received "to main" from :receive

如果提供了 yield_value ，則如果另一個 Ractor 正在調用 take ，則可能會產生該值。在這種情況下，將返回 [:yield, nil] 對：

r1 = Ractor.new(Ractor.current) do |main|
  puts "Received from main: #{main.take}"
end

puts "Trying to select"
r, obj = Ractor.select(r1, Ractor.current, yield_value: 123)
wait
puts "Received #{obj.inspect} from #{r.inspect}"

這將打印：

Trying to select
Received from main: 123
Received nil from :yield

move 布爾標誌定義是否應複製(默認)或移動產生的值。