Ruby Rails 语法说明

Question

class Person < ApplicationRecord
  validates :name, uniqueness: { case_sensitive: false }
end

When a model has above definition, what exactly is happening behind the scenes?

My guess is there exists some validates method and a parameter is passed with symbol name. What is second parameter? a hash with a value that is hash?

Answer 1

First validation :name lets know that Person is not valid without a name attribute.

Second validation uniqueness

This helper validates that the attribute's value is unique right before the object gets saved. It does not create a uniqueness constraint in the database, so it may happen that two different database connections create two records with the same value for a column that you intend to be unique. To avoid that, you must create a unique index on that column in your database.

Third { case_sensitive: false }

There is also a case_sensitive option that you can use to define whether the uniqueness constraint will be case sensitive or not. This option defaults to true

Finally validates :name, uniqueness: { case_sensitive: false }

It means in Person model name attribute must be present with uniqueness not be case sensitive.