with_scope

http://api.rubyonrails.org/classes/ActiveRecord/Base.html#M001343
Scope parameters to method calls within the block. Takes a hash of method_name => parameters hash. method_name may be :find or :create. :find parameters may include the :conditions, :joins, :include, :offset, :limit, and :readonly options. :create parameters are an attributes hash.

In nested scopings, all previous parameters are overwritten by the innermost rule, with the exception of :conditions, :include, and :joins options in :find, which are merged.

:joins options are uniqued so multiple scopes can join in the same table without table aliasing problems. If you need to join multiple tables, but still want one of the tables to be uniqued, use the array of strings format for your joins.

<br /> class Article < ActiveRecord::Base<br /> def self.create_with_scope<br /> #有點像設定 :find 需要加上 :conditions => "blog_id = 1"<br /> # :create 需要加上 :blog_id => 1<br /> with_scope(:find => { :conditions => "blog_id = 1" }, :create => { :blog_id => 1 }) do<br /> find(1) # => SELECT * from articles WHERE blog_id = 1 AND id = 1<br /> a = create(1)<br /> a.blog_id # => 1<br /> end<br /> end<br /> end<br />