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Few people add length validations to fields in their database, and when saving such fields that have exhausted their length, an SQL error occurs. This gem introspects your table schema for maximum lengths on string and text fields and automatically adds length validations to the model.

Due to issues maintaining backwards compatibility, as of v0.8.0 validates_lengths_from_database requires ruby 2 or higher. If you are still using 1.9, please use the v0.7.0 release.

Include the gem using bundler in your Gemfile:

gem "validates_lengths_from_database"

In your model you can activate validations:

class Post < ActiveRecord::Base
  validates_lengths_from_database
end

It also supports filter-style :only and :except options:

class Post < ActiveRecord::Base
  validates_lengths_from_database :only => [:title, :contents]
end

class Post < ActiveRecord::Base
  validates_lengths_from_database :except => [:other_field]
end

If you’d rather specify the limits explicitly instead of pulling them from the database, you can set it:

class Post < ActiveRecord::Base
  validates_lengths_from_database :limit => 255
end

Or to set the limit differently for string (VARCHAR) and (TEXT) columns:

class Post < ActiveRecord::Base
  validates_lengths_from_database :limit => {:string => 255, :text => 4092}
end

Since v0.5.2, it’s possible to use the ‘validate_lengths_from_database` on an abstract parent (without a table), such as ApplicationRecord or ActiveRecord::Base.

class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true
  validates_lengths_from_database :limit => 255
end

# This will use the validations with default options (from parent)
class Post < ApplicationRecord
end

# This will use the validations, with overriding the default options (the limit will not be applied)
class User < ApplicationRecord
  validates_lengths_from_database :only => [:name]
end

# This will use the validations, using the default options + adding some class specific customizations
class Comment < ApplicationRecord
  validate_lengths_from_database_options[:only] << :name
end

This gem uses appraisal to test with different versions of the dependencies. See Appraisal first for which versions are tested.

# Just the gems locked in Gemfile.lock
$ rake test

# All of the Appraisals:
$ appraisal install
$ appraisal rake test