Class: EZMQ::Subscriber

Inherits:
Socket
  • Object
show all
Defined in:
lib/ezmq/subscribe.rb

Overview

Subscribe socket that listens for messages with an optional topic.

Instance Attribute Summary

Attributes inherited from Socket

#context, #decode, #encode, #socket

Instance Method Summary (collapse)

Methods inherited from Socket

#connect, #send

Constructor Details

- (Publisher) initialize(**options)

Note:

The default behaviour is to output and messages received to STDOUT.

Creates a new Subscriber socket.

Parameters:

  • options (Hash) —

    optional parameters.

Options Hash (**options):

  • topic (String) —

    a topic to subscribe to.

See Also:



17
18
19
20
 
# File 'lib/ezmq/subscribe.rb', line 17

def initialize(**options)
  super :connect, ZMQ::SUB, options
  subscribe options[:topic] if options[:topic]
end

Instance Method Details

- (void) listen {|message, topic| ... }

This method returns an undefined value.

By default, waits for a message and prints it to STDOUT.

Yields:

  • (message, topic) —

    passes the message body and topic to the block.

Yield Parameters:

  • message (String) —

    the message received.

  • topic (String) —

    the topic of the message.



57
58
59
60
61
62
63
64
65
66
 
# File 'lib/ezmq/subscribe.rb', line 57

def listen
  loop do
    if block_given?
      yield(*receive)
    else
      message, topic = receive
      puts "#{ topic } #{ message }"
    end
  end
end

- (Object) receive(**options) {|message, topic| ... }

Note:

This method blocks until a message arrives.

Receive a message from the socket.

Parameters:

  • options (Hash) —

    optional parameters.

Options Hash (**options):

  • decode (lambda) —

    how to decode the message.

Yields:

  • (message, topic) —

    passes the message body and topic to the block.

Yield Parameters:

  • message (Object) —

    the message received (decoded).

  • topic (String) —

    the topic of the message.

Returns:

  • (Object) —

    the message received (decoded).



35
36
37
38
39
40
41
42
43
44
45
46
47
 
# File 'lib/ezmq/subscribe.rb', line 35

def receive(**options)
  message = ''
  @socket.recv_string message

  message = message.match(/^(?<topic>[^\ ]*)\ (?<body>.*)/)

  decoded = (options[:decode] || @decode).call message['body']
  if block_given?
    yield decoded, message['topic']
  else
    [decoded, message['topic']]
  end
end

- (Boolean) subscribe(topic)

Note:

By default, a Subscriber filters all incoming messages. Without

Establishes a new message filter on the socket.

calling subscribe at least once, no messages will be accepted. If topic was provided, #initialize calls #subscribe automatically.

prefix will be accepted.

Parameters:

  • topic (String) —

    a topic to subscribe to. Messages matching this

Returns:

  • (Boolean) —

    was subscription successful?



79
80
81
 
# File 'lib/ezmq/subscribe.rb', line 79

def subscribe(topic)
  @socket.setsockopt(ZMQ::SUBSCRIBE, topic) == 0
end

- (Boolean) unsubscribe(topic)

Removes a message filter (as set with subscribe) from the socket.

Parameters:

  • topic (String) —

    the topic to unsubscribe from. If multiple filters with the same topic are set, this will only remove one.

Returns:

  • (Boolean) —

    was unsubscription successful?



90
91
92
 
# File 'lib/ezmq/subscribe.rb', line 90

def unsubscribe(topic)
  @socket.setsockopt(ZMQ::UNSUBSCRIBE, topic) == 0
end