I just want to copy files on google drive! (^^)

Add EasyDrive to your Gemfile.

gem 'easy_drive'

1. You need to enable the Drive API for your app and download client_secrets.json to your project root directory.

   You can do this in your app's API project in the Google APIs Console.

   See further information on google-api-ruby-client-samples

2. Call setup, and both easy_drive-oauth2.json and easy_drive-v2.cache are created in project root directory.

   client = EasyDrive::Client.new
   client.setup # generate above 2 files.
   

client = EasyDrive::Client.new
client.copy(source_file_id, dest_folder_id, {title: 'new file name'})

That's all. Feel free to copy! (^^)

EasyDrive implements other Google Drive APIs.

Gets a file's metadata by ID.

client.get(file_id)

Insert(Upload) a new file.

client.insert('/etc/hello.txt', folder_id, {title: 'This is a new file.'})

Lists the user's all files.

client.list

Search files.

client.list({title: 'TITLE TEXT for searching'})

Search files in a specific folder.

client.list({title: 'TITLE TEXT for searching', folder_id: 'FOLDER_ID'})

EasyDrive is a wrapper of google-api-ruby-client.
So, you can call methods of google-api-ruby-client directly.

easy_drive_client = EasyDrive::Client.new
result = easy_drive_client.client.execute(
  :api_method => easy_drive_client.drive.files.get,
  :parameters => {
    'fileId' => 'file_id',
    'alt' => 'json'
  }
)