client_secrets_usage.rb

gem 'signet', '~> 0.3.0'
require 'signet/oauth_2/client'
gem 'google-api-client', '~> 0.4.3'
require 'google/api_client'
require 'google/api_client/client_secrets'
client_secrets = Google::APIClient::ClientSecrets.load('client_secrets.json')
client = Google::APIClient.new(
  :authorization => Signet::OAuth2::Client.new(
    :client_id => client_secrets.client_id,
    :client_secrets => client_secrets.client_secrets,
    :redirect_uri => client_secrets.redirect_uris.first,
    :authorization_uri =>
      'https://accounts.google.com/o/oauth2/auth',
    :token_credential_uri =>
      'https://accounts.google.com/o/oauth2/token'
  )
)