Ruby Ractor.receive_if用法及代碼示例

receive_if {|msg| block } → msg

僅接收特定消息。

代替 Ractor.receive ， Ractor.receive_if 可以按塊提供模式，您可以選擇接收消息。

r = Ractor.new do
  p Ractor.receive_if{|msg| msg.match?(/foo/)} #=> "foo3"
  p Ractor.receive_if{|msg| msg.match?(/bar/)} #=> "bar1"
  p Ractor.receive_if{|msg| msg.match?(/baz/)} #=> "baz2"
end
r << "bar1"
r << "baz2"
r << "foo3"
r.take

這將輸出：

foo3
bar1
baz2

如果塊返回真值，則消息將從傳入隊列中刪除並返回。否則，消息將保留在傳入隊列中，並且給定塊檢查以下收到的消息。

如果傳入隊列中沒有消息，該方法將阻塞，直到新消息到達。

如果塊被 break/return/exception/throw 轉義，則消息將從傳入隊列中刪除，就好像已返回真值一樣。

r = Ractor.new do
  val = Ractor.receive_if{|msg| msg.is_a?(Array)}
  puts "Received successfully: #{val}"
end

r.send(1)
r.send('test')
wait
puts "2 non-matching sent, nothing received"
r.send([1, 2, 3])
wait

打印

2 non-matching sent, nothing received
Received successfully: [1, 2, 3]

請注意，您不能在給定塊中遞歸調用 receive/receive_if。這意味著您不應該在塊中執行任何任務。

Ractor.current << true
Ractor.receive_if{|msg| Ractor.receive}
#=> `receive': can not call receive/receive_if recursively (Ractor::Error)