On 3/22/10 1:28 AM, alberto wrote:
Hi guys. I would like to give my opinion on the subject. You could
basically sum it up essentially as "please don't reinvent the wheel".
Favor constructor injection for all required services. With the use of
type hints, it makes dependencies very clear and in a clean way. It
also avoids the problem of naming collisions. And I don't think having
to set a couple of vars per controller is really an issue.
The problem is not to set a couple of vars, but the cost associated with
creating the objects themselves.
If you really need an expensive-to-create service which is only needed
for not all of your actions, and it really belongs there, (like the
mailing service you are discussing) then I think it should be lazy
loaded. If you want to relieve the users from having to take care of
that, maybe something at the container level could be implemented to
be able to indicate that when wiring the service. I think it could be
done via dynamic proxies (in the same way Doctrine does, if I am not
mistaken).
The DIC already lazy-load the services. They are only created on demand
when you need them. But if a method needs a service as an argument, of
course we need to create it right away.
Fabien
alberto
On 21 mar, 18:10, Jordi Boggiano<[email protected]> wrote:
On Sun, Mar 21, 2010 at 6:06 PM, Richtermeister<[email protected]> wrote:
I keep seeing the example of the mailer as a dependency of an action,
but in reality, aren't dependencies often conditional?
For example, sending a mail often depends on whether, say, a form
validates. By passing the mailer into the constructor or the method
directly, we would "always" instantiate it, even though it's only
"sometimes" needed.
Having read about the DI container, I was under the impression that
it's lazy loading abilities were supposed to fix just that problem,
that the mailer is only instantiated when I really (!) need it, not
"potentially" need it.
This is only true if you pass the entire container, then when you do
$container->mailer, it instantiates it. If you pass it as a parameter
directly, no matter how, it is indeed instantiated always.
As I previously said, in most cases, the code sending a mail isn't
going to be executed that much that it actually matters, but in some
cases it might. In those cases though, you could always ask for the
$container service itself as a parameter, and fetch the mailer from it
only when really needed.
Cheers,
Jordi
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