named-scope

I have the following scope for my class called Collection : scope :with_missing_coins, joins(:coins).where("coins.is_missing = ?", true) I can run Collection.with_missing_coins.count and get a result back -- it works great! Currently, if I want to get collections without missing coins, I add another scope: scope :without_missing_coins, joins(:coins).where("coins.is_missing = ?", false) I find myself writing a lot of these "opposite" scopes. Is it possible to get the opposite of a scope without sacrificing readability or resorting to a lambda/method (that takes true or false as a parameter)?

I'm trying to create a named_scope that uses a join, but although the generated SQL looks right, the result are garbage. For example: class Clip < ActiveRecord::Base named_scope :visible, { :joins => "INNER JOIN series ON series.id = clips.owner_id INNER JOIN shows on shows.id = series.show_id", :conditions=>"shows.visible = 1 AND clips.owner_type = 'Series' " } (A Clip is owned by a Series, a Series belongs to a Show, a Show can be visible or invisible). Clip.all does: SELECT * FROM `clips` Clip.visible.all does: SELECT * FROM `clips` INNER JOIN series ON series.id = clips.owner_id INNER JOIN

From the book Agile Web Development With Rails class Order < ActiveRecord::Base named_scope :last_n_days, lambda { |days| {:conditions => ['updated < ?' , days] } } named_scope :checks, :conditions => {:pay_type => :check} end The statement orders = Orders.checks.last_n_days(7) will result to only one query to the database. How does rails implement this? I'm new to Ruby and I'm wondering if there's a special construct that allows this to happen. To be able to chain methods like that, the functions generated by named_scope must be returning themselves or an object than can be scoped further.

I have a Rails 3 project. With Rails 3 came Arel and the ability to reuse one scope to build another. I am wondering if there is a way to use scopes when defining a relationship (e.g. a "has_many"). I have records which have permission columns. I would like to build a default_scope that takes my permission columns into consideration so that records (even those accessed through a relationship) are filtered. Presently, in Rails 3, default_scope (including patches I've found) don't provide a workable means of passing a proc (which I need for late variable binding). Is it possible to define a has

Before going for details. Question 1:-- What's the meaning of scope here (ie named **scope )?** what's the benefits of using named scope? Now:- from Agile Development with Rails book:-- class Order < ActiveRecord::Base named_scope :last_n_days, lambda { |days| {:conditions => ['updated < ?' , days] } } named_scope :checks, :conditions => {:pay_type => :check} end Such a named scope would make finding the last week's worth of orders a snap. orders = Orders.last_n_days(7) Scopes can also be combined orders = Orders.checks.last_n_days(7) why we are using named_scope here. We can do the same using

I need to join a table to the a select/group-by query (which includes the same table), and I'd like to do it using Arel. I have a table of :phenotypes which are has_and_belongs_to_many :genes , which are themselves has_and_belongs_to_many :orthogroups . As a result, the relationship between phenotypes and orthogroups are many-to-many. I have two scopes (on Orthogroup) which get all orthogroups associated with a specific phenotype: scope :with_phenotype, lambda { |phenotype_id| where("observations.phenotype_id = ?", phenotype_id). joins("inner join orthologies on (orthologies.orthogroup_id =