Re: Is IoC containers harmful for DDD?

On Tue, 2 Dec 2014 05:24:23 -0800
"Greg Young [email protected] [domaindrivendesign]"
<[email protected]> wrote:

> How does a plugin architecture interfere with using a bootstrap
> method? It is quite common to do both (even compiling the bootstrap
> code at start). This has been a common practice in functional
> languages for decades.
> 

Bootstrap without the container in non-trivial scenarios results in
poor main container.
You said one of the examples, you want to inject transaction in
repository, so return Func instead.
Which is a good solution if thats the only use case - transaction per
session.

But whenever I see such examples (Cake in Scala) I'm not sure that
people bashing containers used it for non-trivial examples.
In their defense, JVM containers don't support many of useful scenarios
(like nesting contexts) so I can see from where they are coming from.

For example, your example for app service where you converted class to
a function by providing it by explicit repository instance is not
really something you can get away in plugin systems. For couple of
reasons:

1) You don't really know dependencies of that class - you can use
reflection to look them up - but again going into poor man Ioc land
2) You don't know context for that object in advance - thus, delegating
work of injecting correct context to someone else (whether it's global
context, thread context, session context, using context) simplifies
domain code a lot (not going into discussion about other people's
code). I've also seen systems which assume there are only couple of
contexts: global and thread, which fail to work in event style way,
since context is neither global, nor thread.

But then, I don't want to argue about IoC, especially since you said
they have their place and uses, just saying I find you example of
replacing IoC bootstrap with manual configuration misleading.

Regards,
Rikard

-- 
Rikard Pavelic
https://dsl-platform.com/
http://templater.info/


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Posted by: Rikard Pavelic <[email protected]>
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