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### 8.1 Development Overview

EDE is made up of a series of classes implemented with EIEIO. These classes define an interface that can be used to create different types of projects.

EDE defines two superclasses which are `ede-project` and `ede-target`. All commands in EDE are usually meant to address the current project, or current target.

All specific projects in EDE derive subclasses of the EDE superclasses. In this way, specific behaviors such as how a project is saved, or how a target is compiled can be customized by a project author in detail. EDE communicates to these project objects via an API using methods. The commands you use in EDE mode are high-level functional wrappers over these methods.

Some example project types are:

`project-am`

  Automake project which reads existing Automake files.

`ede-proj-project`

  This project type will create `Makefiles`, or `Makefile.am` files to compile your project.

`ede-linux`

  This project type will detect linux source trees.

`ede-emacs`

  This project will detect an Emacs source tree.

There are several other project types as well.

The first class you need to know to create a new project type is `ede-project-autoload`. New instances of this class are needed to define how Emacs associates different files/buffers with different project types. All the autoloads are kept in the variable `ede-project-class-files`.

The next most important class to know is `ede-project`. This is the baseclass defines how all projects behave. The basic pattern for a project is that there is one project per directory, and the topmost project or directory defines the project as a whole.

Key features of `ede-project` are things like name and version number. It also holds a list of `ede-target` objects and a list of sub projects, or more `ede-project` objects.

New project types must subclass `ede-project` to add special behavior. New project types also need to subclass `ede-target` to add specialty behavior.

In this way, the common EDE interface is designed to work against `ede-project`, and thus all subclasses.

`ede-project` subclasses `ede-project-placeholder`. This is the minimum necessary project needed to be cached between runs of Emacs. This way, Emacs can track all projects ever seen, without loading those projects into memory.

Here is a high-level UML diagram for the EDE system created with COGRE..

    +-----------------------+        +-----------------------+
    |                       |        |ede-project-placeholder|
    |ede-project-class-files|        +-----------------------+
    |                       |        +-----------------------+
    +-----------------------+        +-----------------------+
               /\                                ^
               \/                               /_\
                |                                |
     +--------------------+                +-----------+         +----------+
     |ede-project-autoload|                |ede-project|         |ede-target|
     +--------------------+<>--------------+-----------+<>-------+----------+
     +--------------------+                +-----------+         +----------+
     +--------------------+                +-----------+         +----------+
                                                 ^
                                                /_\
                                                 |
                           +---------------------+-----------------+
                           |                     |                 |
                           |                     |                 |
                           |                     |                 |
                  +----------------+   +-------------------+  +---------+
                  |ede-proj-project|   |project-am-makefile|  |ede-emacs|
                  +----------------+   +-------------------+  +---------+
                  +----------------+   +-------------------+  +---------+
                  +----------------+   +-------------------+  +---------+

Next: Detecting a Project, Previous: Extending EDE, Up: Extending EDE [Contents]