Extending existing Models/Classes

Foo.md

Flow builds for most classes a proxy for Dependency injection, lazy loading, etc it does this by creating a new file in the Code Cache that contains the contents of the original class appended with the suffix "_Original" and a class with the name of the real className that inherits from that, in this class is some magic for dependency injection, aop and lazy loading. For example:

Given we have a class named \My\Package\Foo
Then Flow will create a file called My_Package_Foo.php
This file contains the code of the class "\My\Package\Foo" with a className suffix "_Original" -> \My\Package\Foo_Original
This file also contains di, aop, and lazyloading code in the generated "\My\Package\Foo" class that inherits from \My\Package\Foo_Original

Proposal

We could use this mechanism, to enable users to "Inject" whole classes in between the generated and the original class like this:

Objects.yaml

'\My\Package\Foo'
  inject:
    - 
      className: \Some\Package\FooExtension
      position: start
    

This would trigger the ProxyBuilder to create an extension chain like this:

<?php
namespace \My\Package;
class Foo_Original {
  // Code from the original classname
}

namespace \Some\Package;
class FooExtension extends \My\Package\Foo_Original {

}

namespace \My\Package;
class Foo extends Foo_Original extends \Some\Package\FooExtension {
  // Generated by the ProxyBuilder containing di, aop, etc
}

Instead of this:

'\My\Package\Foo'
  inject:
    - 
      className: \Some\Package\FooExtension
      position: start

what about this:

class Foo {
    //original stuff here
}

/**
 * @Flow\Expands(\My\Package\Foo)
 */
class FooExtension {
    //extra stuff here
}

Another thought: instead of making FooExtension be a parent class of class Foo, we could have AOP introduce the extra features as traits.