Ruby on Rails - Anidado with_scope

Este ejemplo muestra cómo podemos anidar with_scope para obtener diferentes resultados según los requisitos.

# 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

Ahora, verifique otro ejemplo de cómo el alcance es acumulativo.

# 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

Un ejemplo más que muestra cómo se ignora el alcance anterior.

# 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