Rails is all about patterns and when you're creating models, it's important to set pattern-based rules before you publish to your database. Below are simply a few pattern categories and I'll continue to add more over time.
Validates the uniqueness of a field.
# Artists must have a unique name validates :name, uniqueness: true
Validates the presence of data.
validates :title, presence: true
Validate the format of an e-mail.
validates_format_of :email,:with => /\A[^@\s]+@([^@\s]+\.)+[^@\s]+\z/
validates_associated :songs, :albums, :tracks