Class: Synapse::Message

Inherits:
Object
  • Object
show all
Defined in:
lib/synapse/common/message.rb

Overview

Representation of a message containing a payload and metadata

Instead of using this class directly, it is recommended to use a subclass specifically for commands, events or domain events.

Two messages with the same identifier should be interpreted as different representations of the same conceptual message. In such case, the metadata may be different for both representations. The payload may be identical.

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(id, metadata, payload, timestamp) ⇒ undefined

Parameters:

  • id (String)
  • metadata (Hash)
  • payload (Object)
  • timestamp (Time) 


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# File 'lib/synapse/common/message.rb', line 34

def initialize(id, metadata, payload, timestamp)
  @id = id
  @metadata = metadata
  @payload = payload
  @timestamp = timestamp

  @metadata.freeze
end

Instance Attribute Details

#id ⇒ String (readonly)

Unique identifier of this message

Returns:

  • (String) 


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# File 'lib/synapse/common/message.rb', line 13

def id
  @id
end

#metadata ⇒ Hash (readonly)

Metadata attached to this message by the application

Returns:

  • (Hash) 


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# File 'lib/synapse/common/message.rb', line 17

def metadata
  @metadata
end

#payload ⇒ Object (readonly)

Payload of this message; examples include commands and events. A payload is expected to be immutable to provide thread safety.

Returns:

  • (Object) 


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# File 'lib/synapse/common/message.rb', line 23

def payload
  @payload
end

#timestamp ⇒ Time (readonly)

Timestamp recorded when the message was created

Returns:

  • (Time) 


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# File 'lib/synapse/common/message.rb', line 27

def timestamp
  @timestamp
end

Class Method Details

.as_message(object) ⇒ Message

Wraps an object into a message as its payload

If the given object is an message, it will be returned unchanged.

Parameters:

  • object (Object)

Returns:



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# File 'lib/synapse/common/message.rb', line 81

def self.as_message(object)
  unless object.is_a? Message
    object = self.build do |builder|
      builder.payload = object
    end
  end

  object
end

.build {|MessageBuilder| ... } ⇒ Message

Yields a message builder that can be used to produce a message

Yields:

Returns:

See Also:



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# File 'lib/synapse/common/message.rb', line 96

def self.build(&block)
  builder.build &block
end

.builder ⇒ Class

Returns the type of builder that can be used to build this type of message

Returns:

  • (Class) 


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# File 'lib/synapse/common/message.rb', line 102

def self.builder
  MessageBuilder
end

Instance Method Details

#and_metadata(additional_metadata) ⇒ Message

Returns a copy of this message with the given metadata merged in

Parameters:

  • additional_metadata (Hash)

Returns:



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# File 'lib/synapse/common/message.rb', line 55

def and_metadata(additional_metadata)
  return self if additional_metadata.empty?

  builder = self.class.builder.new
  build_duplicate builder, @metadata.merge(additional_metadata)
  builder.build
end

#payload_type ⇒ Class

Returns the class of the payload of this message; use this instead of calling payload and class, in case of lazily deserializing messages.

Returns:

  • (Class) 


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# File 'lib/synapse/common/message.rb', line 47

def payload_type
  @payload.class
end

#with_metadata(replacement_metadata) ⇒ Message

Returns a copy of this message with the metadata replaced with the given metadata

Parameters:

  • replacement_metadata (Hash)

Returns:



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# File 'lib/synapse/common/message.rb', line 67

def with_metadata(replacement_metadata)
  return self if @metadata == replacement_metadata

  builder = self.class.builder.new
  build_duplicate builder, replacement_metadata
  builder.build
end