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class GroupersController < ApplicationController::Base
def create
@grouper = current_member)
redirect_to home_path
render :new
# app/mailers/confirmed_grouper_emails.rb
class ConfirmedGrouperEmails
def initialize(grouper)
@grouper = grouper
def deliver
WingMailer.grouper_confirmed(wings: @grouper.wings.pluck(:id)).deliver
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adomokos commented Mar 4, 2014

Why did you make ConfirmedGrouperEmails statefull? Could you just make the #deliver method a class method and pass @grouper to it as an argument?

I guess the real question is: what is your thinking about making objects statefull vs. stateless?

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jonahx commented Mar 4, 2014

It's not stateful in any meaningful sense. Yes, it has a member variable, but there's no way to mutate it. It is essentially nothing more than syntactic sugar over deliver(grouper)

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tel commented Mar 4, 2014

I've never understood this style—though it appears popular. There's seems to be no improvement over deliver(grouper). I feel like it's just making use of the fact that you built a class to organize this component so you "may as well" use the initializer.

That said, I think if it were truly just a function it'd be a bit strange since in Ruby you kind of rely on classes to provide semantic grouping.

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clemens commented Mar 4, 2014

The advantage is quite simple: At some point there might have to be some kind of state – this is where you'd then either convert all consumers of your ConfirmedGrouperEmails API to use the instantiated version or provide a kind of wrapper to have the class method create an instance and deliver it by calling ConfirmedGrouperEmails.deliver(grouper). This is not premature optimization but a real issue.

Simply put: Don't use class methods unless you really have to. Ruby is an OOP language so use OOP.

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jonahx commented Mar 4, 2014

In this specific example you're right, there's no improvement. But if you were to add other methods beyond deliver, which also make use of @grouper, then you get the improvement of not having to pass the parameter around constantly. It's not really any different than preferring "hello".upcase to something like uppercase("hello")

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dideler commented Mar 7, 2014

@tel I think the improvement is readability: .deliver(grouper) comes across as delivering a grouper, while .deliver is read as simply delivering whatever it was called on.

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shime commented May 6, 2014

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eprothro commented Oct 13, 2015

@shime 👍

Put another way, passing the argument to a class method is not "exemplary" (a la Sandi Metz). So future development efforts (often by other devs) are likely harmed, since this pattern resists refactoring.

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