[rspec-users] Design Pattern proposal for better Rails development

David Chelimsky dchelimsky at gmail.com
Wed Nov 5 08:24:04 EST 2008

On Wed, Nov 5, 2008 at 7:17 AM, Fernando Perez <lists at ruby-forum.com> wrote:
> The biggest problems I have when developing (beside stupid typos) are:
> 1) The name of a method which I often change to a supposedly  more
> descriptive name, which I will eventually change to an even more
> supposedly descriptive name
> 2) The arguments a method takes
> Let's say I have a class method: Product.find_if_purchased(product_id,
> user_id)
> Let's say it is called in 3 different controllers.
> Now I want to change the name of the method to make it more clear and at
> the same time I will throw a new argument to it:
> Product.find_if_purchased_by_user_id(product_id, user_id, site_id)
> Now this means I have to change the code in three controllers, and also
> change the specs that test it with should_receive(:find_if_purchased).
> This is painful.
> And it demonstrates that controllers are tightly coupled to models which
> shouldn't be the case. Therefore we need names that don't vary over
> time. We want our models and controllers to work in a black box manner.
> So based on the design pattern "convention over configuration", why not
> use methods such as:
> Product.find_for_products_index or ..._show, that are named after their
> controller and action where they are called?
> Moreover, instead of hardcoding the arguments that it requires, why not
> pass a hash of arguments which is much more flexible? Indeed, when using
> hardcoded arguments, if let's say I want to define a default value for
> product_id, then again I must change all code that calls it, because in
> Ruby, arguments that have default values must be defined last.
> What do you think about my idea? I have been trying it recently, and I
> find it more pleasant to work with. It also prevents me from putting too
> much code inside the controllers.
> They are drawbacks though:
> 1) the name of the method is not descriptive, a little comment in the
> controller helps well here.
> 2) when the method is reused by many actions, we need to create "dummy"
> methods that simply call the real method. For instance,
> find_for_products_show just passes the arguments to another method
> called find_for_subscriptions_show which is where the real code sits
> 3) there is a slight performance hit

4) as the names become more similar they become harder to find :)

For me, I think having descriptive names that are easy to find makes
it much easier to change the things I want to change. Just search and


> Has anyone experienced such thing? The idea came to me yesterday when
> trying to spec a chain of named_methods. I realized that the chain of
> named_methods doesn't belong to the controller, it should be wrapped in
> a dummy method that calls the named_scopes.
> Best regards,
> --
> Posted via http://www.ruby-forum.com/.
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