Ruby on Rails Models

Coding Style and Conventions

The following order is suggested: extends, includes, associations, validations, enumerations, scopes, class and object methods. Everything in alphabetical order.
belongs_to associations come first, followed by has_manyassociations. Any other kind of association comes after has_many. Break line between kinds of associations, but not between associations of the same kind.
Sentences like accepts_nested_attributes_for come after associations.
Validate associations first and attributes last. Break line between associations and attributes validations, but not between validations of the same kind. Enumerations are validated on theirs declarations.
Always use datetime for date attributes, even if in the MER it's defined as DATE.

Prefer use of hash validations, like validates :name, presence: true, for presence, inclusion, etc.
Please, do not validate multiple attributes in the same line. Declare a validates sentence for each association or attribute.
When use custom validation, create a class in app/validations with custom validation and call validates_with in model, see our example.
Validate object under the foreign_key.
Never validate presence of boolean, nor it should be tested. Use validates :boolean_attr, inclusion: [true, false] instead.

Prefer scopes under class methods.
When query is much complex, create a query class into app/queries
Keep simple methods in model, like update an attribute (without condition) and simple queries.