[TYPO3-dev] Hooks with interface

[Ingo Renner]

Dmitry Dulepov wrote:

Hi Dmitry,

> Steffen Kamper wrote:
>> yes, something like that - latest RFCs with new hooks were all rejected
>> if they don't come with an interface.
>
> I do not remember that core team decided to support only interfaces for hooks.

just because you don't remember doesn't mean it isn't that way ;)

Interfaces define a clear contract with the core - which userFunc 
doesn't. You'll imidiately notice when not sticking to that contract.

Having that strict contract is a good thing:

* you know which methods to implement with which parameters
* you'll notice if something is wrong
* you'll notice if the interface changed

Now, attention to the third point: Using interfaces for the first time 
allows us to actually modify hooks! Of course it will limit backwards 
compatability in some way, but only in a very controlled and clear way.

If an extension uses a hook that requires the implementation of an 
interfaces it does so by fullfilling the interface's contract. If we now 
would change that contract the author would notice that, which is not 
the case with hooks implemented through userFunc, is it?
This results in another advantages for extension authors:

* they imidiately see what's the problem
* they know how to solve the problem (by implementing the missing methods)
* they can limit a certain version of an extension to a certain version 
of the TYPO3 core

For the core this results in the following advantages:

* we can change hooks (!) (though we should be carful with it of course)
* we do not have to worry about breaking something badly (as others will 
notice and be notified about what to do by PHP)
* changes in interfaces are easily traceable


I hope that brought bake some memories why interfaces are so much better 
for every one.


all the best
Ingo

-- 
Ingo Renner
TYPO3 Core Developer, Release Manager TYPO3 4.2