09 Multipart Artifacts¶

Run it:

bundle exec ruby examples/run 09_multipart

What it shows: a single artifact carrying all four Part types — text, json, binary, and url — and how the client uses predicate methods to dispatch on part type.

Files¶

File	Purpose
`examples/09_multipart/server.rb`	`ReportExecutor` builds one four-part artifact covering every `Part` constructor
`examples/09_multipart/client.rb`	Iterates artifact parts; uses `text?`, `json?`, `raw?`, `url?` to process each type

The four Part types¶

Constructor	Transport format	Client accessor
`Part.text(str, media_type:)`	Plain string	`part.text`
`Part.json(hash, filename:)`	JSON object	`part.data`
`Part.binary(bytes, media_type:, filename:)`	Base64-encoded string	`part.decoded_bytes`
`Part.from_url(url, media_type:, filename:)`	URL string, no inline content	`part.url`

Server — `ReportExecutor`¶

def call(ctx)
  topic = ctx.message.text_content.strip

  summary = A2A::Models::Part.text(<<~TEXT, media_type: "text/plain")
    Report on: #{topic}
    Generated at #{Time.now.utc.iso8601}
  TEXT

  metadata = A2A::Models::Part.json(
    { "topic" => topic, "word_count" => topic.split.length, "confidence" => 0.92 },
    filename: "metadata.json"
  )

  csv_bytes = build_csv(topic).b
  csv_part  = A2A::Models::Part.binary(
    csv_bytes, media_type: "text/csv", filename: "term_scores.csv"
  )

  url_part = A2A::Models::Part.from_url(
    "https://en.wikipedia.org/wiki/Special:Search?search=#{URI.encode_uri_component(topic)}",
    media_type: "text/html",
    filename:   "reference.html"
  )

  ctx.task.complete!(artifacts: [
    A2A::Models::Artifact.new(name: "report", parts: [summary, metadata, csv_part, url_part])
  ])
end

Client — type-safe dispatch¶

artifact.parts.each do |part|
  if part.text?
    puts part.text

  elsif part.json?
    puts JSON.pretty_generate(part.data)

  elsif part.raw?
    bytes = part.decoded_bytes
    puts "#{bytes.bytesize} bytes (#{part.media_type})"
    puts bytes.force_encoding("UTF-8")

  elsif part.url?
    puts part.url
  end
end

The predicates text?, json?, raw?, and url? are mutually exclusive. decoded_bytes reverses the base64 encoding that the transport layer applies to binary parts.

Protocol coverage¶

Spec section	What the demo shows
`Part.text`	Plain prose with `media_type: "text/plain"`
`Part.json`	Structured data as a Ruby Hash; serialized as a JSON object in the artifact
`Part.binary`	Raw bytes base64-encoded for transport; `decoded_bytes` restores the original
`Part.from_url`	URL reference with `media_type` and `filename`; no content is inlined
`Part` predicates	`text?`, `json?`, `raw?`, `url?` allow type-safe dispatch on the receiving end
Multi-part `Artifact`	One artifact contains all four parts; clients can select the representation they need
`Artifact.name`	Named artifact (`"report"`) for client-side identification