Ruby code for YouTube API v3 integration from http://bdunagan.com/2014/09/06/ruby-integration-with-youtube-api-v3

youtube-api-v3.rb

# List of all uploaded videos and playlists on a YouTube Channel
# Note that YouTube API v3 requires a key. Create a browser API key with a referer at https://console.developers.google.com.
#
# Here are the steps using "curl" that matches the Ruby code below:
#
# Get channel information.
# curl --referer "YOUR_REFERER" "https://www.googleapis.com/youtube/v3/channels?part=snippet,contentDetails,statistics,status&maxResults=50&forUsername=YOUR_USERNAME&key=YOUR_KEY"
# Find "Uploads" playlist ID at items => contentDetails => relatedPlaylists => uploads.
# Find Channel ID at items => id.
#
# Get playlist items for "Uploads".
# curl --referer "YOUR_REFERER" "https://www.googleapis.com/youtube/v3/playlistItems?part=snippet&maxResults=50&playlistId=YOUR_PLAYLIST_ID&key=YOUR_KEY"
# curl --referer "YOUR_REFERER" "https://www.googleapis.com/youtube/v3/playlistItems?part=snippet&maxResults=50&pageToken=PAGE_TOKEN&playlistId=YOUR_PLAYLIST_ID&key=YOUR_KEY"
#
# Get playlists for channel.
# curl --referer "YOUR_REFERER" "https://www.googleapis.com/youtube/v3/playlists?part=snippet&maxResults=50&channelId=YOUR_CHANNEL_ID&key=YOUR_KEY"

require 'net/http'
require 'json'

def youtube_v3_api(path)
  # Create URI.
  uri = URI.parse("https://www.googleapis.com/youtube/v3/#{path}")
  # Create API request.
  request = Net::HTTP.new(uri.host, uri.port)
  request.use_ssl = true
  request.verify_mode = OpenSSL::SSL::VERIFY_NONE
  # Execute request.
  response = request.get(uri.request_uri, {"Referer" => "#{@referer}"})
  # Parse response if any.
  return (response.code == "200") ? JSON.parse(response.body) : nil
end

# Setup environment.
@api_key = "YOUR_API_KEY"
@referer = "YOUR_REFERER"
@username = "YOUR_USERNAME"

# Get "Uploads" playlist ID for username
results = youtube_v3_api("channels?part=snippet,contentDetails,statistics,status&maxResults=50&forUsername=#{@username}&key=#{@api_key}")
jj results
@uploads_playlist_id = results["items"][0]["contentDetails"]["relatedPlaylists"]["uploads"]

# Get "Uploads" playlist items.
results = youtube_v3_api("playlistItems?part=snippet&maxResults=50&playlistId=#{@uploads_playlist_id}&key=#{@api_key}")
playlist_items = results["items"]
while results["nextPageToken"]
  # Add additional items if results are paged.
  results = youtube_v3_api("playlistItems?part=snippet&maxResults=50&pageToken=#{results["nextPageToken"]}&playlistId=#{@uploads_playlist_id}&key=#{@api_key}")
  playlist_items += results["items"]
end
# Get videos with statistics for playlist items.
videos = []
playlist_items.each_slice(10) do |items|
  video_ids = items.collect {|item| item["snippet"]["resourceId"]["videoId"] }
  results = youtube_v3_api("videos?part=snippet,statistics,contentDetails&id=#{video_ids.join(",")}&key=#{@api_key}")
  videos += results["items"]
end
jj videos

# Get playlists for username.
results = youtube_v3_api("channels?part=snippet,contentDetails,statistics,status&maxResults=50&forUsername=#{@username}&key=#{@api_key}")
@channel_id = results["items"][0]["id"]
results = youtube_v3_api("playlists?part=snippet&maxResults=50&channelId=#{@channel_id}&key=#{@api_key}")
playlists = results["items"]
jj playlists

My bad. I hadn't wrapped the url in quotes! Perfect. Many thanks.