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Mario
Mario

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Boolean Validator for Rails

#rails #ruby #activerecord

Rails doesn't come with a built-in boolean validator.
That means if we have boolean attribute and we set it to nil, it defaults to false, which is not necessarily what we want.

For example a SchrodingersCat model with a alive boolean attribute:

cat = SchrodingersCat.new(alive: nil) cat.valid? # => true
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To solve that problem we can add a custom validator:

# app/validators/boolean_validator.rb class BooleanValidator < ActiveModel::EachValidator def validate_each(record, attribute, value) return if value.in? [false, true] record.errors.add attribute, :boolean end end
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Then we can use that validator the same way as the built-in ones:

# app/models/schrodingers_cat.rb class SchrodingersCat < ApplicationRecord validates :alive, boolean: true end
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The error message can be defined for example in activerecord.errors.messages.boolean:

# config/locales/en.yml en: activerecord: errors: messages: boolean: "must be boolean"
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The result:

cat = SchrodingersCat.new(alive: nil) cat.valid? # => false cat.errors.to_a # => ["Alive must be boolean"]
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