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Dropbox Class

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

Introduction

Dropbox 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.

Usage example

var $ftp : cs.FileTransfer_Dropbox
$ftp:=cs.FileTransfer_Dropbox.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_dropbox". 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)

Installation

Dropbox provides a command line tool supporting all standard file transfer operations: dbxcli

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 Apache License,

If Dropbox changes the API, just download their latest release and replace the binary.

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

For Windows the downloaded version could be placed in Resources folder and so easily deployed.

For Mac, you can either use my (new compiled and signed, based on 3.0.0) or compile and sign yourself, to allow shipping it as notarized merged application inside the Resource folder. The version published on GitHub (March 2022) is linked with macOS 10.9 and so too old to be notarized. The precompiled version is in /optional/dbxcli_Mac_precompiled. There is also a "HowToCompileYourself.txt" file, giving hints how to compile and sign yourself.

Copy class methods:
FileTansfer_Dropbox.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 Dropbox 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, open on the target computer a terminal window (on Windows you can also use a console window). Drag and drop from resource folder dbxcli (Mac) or dbxcli.exe (Windows) into the window, to get the correct file path and type " ls" (note the space before ls). Press enter. This displays a message with a https link, such as: It will ask for access:

Go to
https://www.dropbox.com/1/oauth2/authorize?client_id=07o54gulcj8qi35&response_type=code&state=state
Click “Allow” (you might have to log in first).
Copy the authorization code. Enter the authorization code here:

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

The authentication will stay valid till you either use "dbxcli logout" or using a browser opening the Dropbox preferences / Linked Apps and delete the "dbxcli-personal" entry.

Class Documentation

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