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Readme_GDrive.MD

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GDrive Class

Using "Gdrive Command Line Interface" - providing an easy to use wrapper

Introduction

Google Drive or GDrive is a well known cloud based file hosting service. Usually working as synchronization service, to mirror a folder on the computer hard disk with the cloud.

In most cases this is also the easiest usage with 4D. Just define a folder on your disk to sync, and by writing/reading files from 4D to this folder, you also update the files in the cloud storage. This allows storage of external documents, such as PDF representation of invoices, or having an external backup (using 4D Backup in combination with 4D build in encryption).

In some cases you might need more control. You might want to upload files to the cloud which you do not want to store locally any longer or you need to control exactly when they are uploaded and control if this happened successfully.

This class also allows to import and export GDrive documents and so convert Google Docs, Google Spreadsheets, Google Presentations or other formats into local desktop formats, such as PDF, Word or Excel formats, or vice versa.

Usage example

var $ftp : cs.FileTransfer_GDrive
$ftp:=cs.FileTransfer_GDrive.new()
$source:="/product/4D.dmg"
$target:=Convert path system to POSIX(System folder(Desktop))
$result:=$ftp.download($source; $target)
If ($result.success)
	...
End if

For more examples see the method "test_gdrive". Check the download part of the method to see how to use progress bar with Cancel Button.

Feature overview

  • Upload
  • Download
  • Directory Listing
  • Rename and Delete (file and directory)
  • Import and Export

GDrive Class works similar to Dropbox or cURL Class (FTP/FTPS) for compatibility reasons, but internally GDrive is based on file IDs and not File names or paths. As result, whenever you pass a name/path, internally the class first execute a find process to detect the ID and then execute a download, upload or rename command. While this is fine for comfort, it slows down the operation. In cases you are calling directory listing upfront anyway and you do not need compatibility with Dropbox or cURL, it make sense to write your code using IDs directly.

Installation

There is an open source command line tool to use Google Drives supporting all standard file transfer operations: gdrive

The tool is written in the language 'go', which allows a compilation of an executable without any dependencies. This means you an easily deploy it as part of your application (in Resource folder or similar), it uses the MIT License

You can compile it yourself (see instruction in link above), download a precompiled version from Dropbox's github account or use the enclosed one.

To use and deploy we advise to download yourself from github/releases.

For Windows, just copy in resource folder for easy deployment. For Mac: sign it, and then sign/notarize the embedding 4D application. To sign enter by example:

codesign –-force --options runtime --timestamp –-sign "Developer ID Application: 4D Deutschland GmbH" /Users/thomas/Desktop/gdrive

If Gdrive changes the API, just download the latest release from the github repository.

Copy class methods:
FileTansfer_GDrive.4dm
SytemWorkerProperties.4dm
Project Method ErrorHandler.4dm

If you already have a silent ErrorHandler method (no output, just to prevent an error message displayed on screen, error handled by code), just use your existing one.

Method ProgressCallback.4dm can be used as example how to create a progress bar - if needed.

Copy this 2-4 files into your project, done.

Authentication

For security reasons GDrive does not allow to login just with password, you need to create a token and allow the application to work. This needs to be executed on the customer computer, using Terminal/Console and a browser, but it needs to be done only once. Meaning as soon you "registred" this computer, communication can run headless by code without needing any credentials (as long as the logout command is not used).

To authenticate (requires installation upfront, see above), open on the target computer a terminal window (on Windows you can also use a console window).

Enter gdrive list
Press enter. This displays a message with a https link, such as:

Authentication needed Go to the following url in your browser: https://accounts.google.com/o/oauth2/auth?access_type=offline&client_id=12412363245234-7n0vsd234akeruo2fjinrecpdoe99eg.apps.googleusercontent.com&redirect_uri=urn%3Aietf%3Awg%3Aoauth%3A2.0%3Aoob&response_type=code&scope=https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fdrive&state=state

Enter verification code:

Copy the link to a browser and open it. This might require to authenticate using standard Google web forms (skipped if you used Google already and are already authenticated).
Copy the displayed code and paste it in the terminal window. Done.

The authentication will stay valid till you delete the local token file, which is located in the user directory, subdirectory ".gdrive" (invisible folder), named "token_v2.json".

Class Documentation

See Class documentation (in 4D use Explorer/Documentation)
Documentation online