Ruby on Rails - scopes in ruby on rails- ruby on rails tutorial - rails guides - rails tutorial - ruby rails
- Scopes act as predefined filters on ActiveRecord models.
- A scope is defined using the scope class method.
Example
class Person < ActiveRecord::Base
#attribute :first_name, :string
#attribute :last_name, :string
#attribute :age, :integer
# define a scope to get all people under 17
scope :minors, -> { where(age: 0..17) }
# define a scope to search a person by last name
scope :with_last_name, ->(name) { where(last_name: name) }
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Scopes can be called directly off the model class:
minors = Person.minorsClicking "Copy Code" button will copy the code into the clipboard - memory. Please paste(Ctrl+V) it in your destination. The code will get pasted. Happy coding from Wikitechy - ruby on rails tutorial - rails guides - ruby rails - rubyonrails - learn ruby on rails - team
Scopes can be chained:
peters_children = Person.minors.with_last_name('Peters')Clicking "Copy Code" button will copy the code into the clipboard - memory. Please paste(Ctrl+V) it in your destination. The code will get pasted. Happy coding from Wikitechy - ruby on rails tutorial - rails guides - ruby rails - rubyonrails - learn ruby on rails - team
The where method and other query type methods can also be chained:
mary_smith = Person.with_last_name('Smith').where(first_name: 'Mary')Clicking "Copy Code" button will copy the code into the clipboard - memory. Please paste(Ctrl+V) it in your destination. The code will get pasted. Happy coding from Wikitechy - ruby on rails tutorial - rails guides - ruby rails - rubyonrails - learn ruby on rails - team
- Behind the scenes, scopes are simply syntactic sugar for a standard class method.
Example
scope :with_last_name, ->(name) { where(name: name) }
# This ^ is the same as this:
def self.with_last_name(name)
where(name: name)
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Default Scope
- There is one notable difference between the scope method and a class method: scope-defined scopes will always return an ActiveRecord::Relation, even if the logic within returns nil. Class methods, however, have no such safety net and can break chainability if they return something else.