Validation offers simple way to disable the updating and creation of invalid models to your database.

Presence validator

The presence validation ensure than a column is not NULL inside the database. While we encourage to use the NOT NULL feature of PostgreSQL, the presence validator is automatically setup via the typing of the column:

• column x : String is assumed to be present

• column x : String can be nilable

• column x : String, presence: false will assume the value cannot be NULL in the database, while not performing any validation check. This is great for values which have default database set value (ex: serial, timestamp...)

Custom validation

To create a custom validator, just override the validate method:

class Article
  include Clear::Model
​
  column name : String
  column description : String
​
  def validate
    if description_column.present?
        if description.size < 100
          add_error("description", "must contains at least 100 characters")
        end
    end
  end
end

Helpers methods

To simplify the writing of validation code, you may want to use on_presence(field, &block) or ensure_than(field, message, &block) built-in helpers:

class Article
  include Clear::Model
​
  column name : String
  column description : String
​
  def validate
    ensure_than :description, "must contains at least 100 characters", &.size.<(100)
  end
end

The code above will perform exactly like the previous one, while keeping a more compact syntax.

Error object

Whenever a validation check is failing, an error is created and stored in the model. Error is simply a structure with two fields: column : String? and reason : String

The list of error can be accessed through errors method:

a = Article.new
a.content = "Lorem ipsum"
​
unless a.valid?
  a.errors.each do |err|
    puts "Error on column: #{err.column} => #{err.reason}"
  end
end