Ruby-on-rails-rails-with-scope

Ruby on Rails-with_scopeのネスト

この例は、要件に基づいてさまざまな結果を取得するために with_scope をネストする方法を示しています。

# SELECT *FROM employees
# WHERE (salary > 10000)
# LIMIT 10
# Will be written as

Employee.with_scope(
   :find => { :conditions => "salary > 10000",
   :limit => 10 }) do
   Employee.find(:all)
end

ここで、スコープが累積する別の例を確認してください。

# SELECT* FROM employees
# WHERE ( salary > 10000 )
# AND ( name = 'Jamis' ))
# LIMIT 10
# Will be written as

Employee.with_scope(
   :find => { :conditions => "salary > 10000", :limit => 10 }) do
      Employee.find(:all)
      Employee.with_scope(:find => { :conditions => "name = 'Jamis'" }) do
      Employee.find(:all)
   end
end

前のスコープがどのように無視されるかを示すもう1つの例。

# SELECT * FROM employees
# WHERE (name = 'Jamis')
# is written as

Employee.with_scope(
   :find => { :conditions => "salary > 10000", :limit => 10 }) do
   Employee.find(:all)

   Employee.with_scope(:find => { :conditions => "name = 'Jamis'" }) do
      Employee.find(:all)
   end

   # all previous scope is ignored
   Employee.with_exclusive_scope(:find => { :conditions => "name = 'Jamis'" }) do
      Employee.find(:all)
   end
end