You can find the in-depth documentation about FieldTypes and their best practices. It describes how each component of a FieldType interacts with the various layers of the system, and how to implement those.
About this tutorial
This tutorial aims at covering the conception and development of a custom eZ Publish 5 FieldType.
We will do this by implementing a Tweet Field Type. It will:
Getting the code
The code created throughout this tutorial is available on github: https://github.com/ezsystems/TweetFieldTypeBundle.