Params
Probably the most common use case is to validate HTTP params. This is a special kind of a validation for a couple of reasons:
- The input is a hash with stringified keys
- The input can include values that are strings, hashes or arrays
- Prior to validation, we need to symbolize keys and coerce values based on the information in a schema
For that reason, dry-schema ships with Params schemas:
schema = Dry::Schema.Params do
required(:email).filled(:string)
required(:age).filled(:integer, gt?: 18)
end
errors = schema.call('email' => '', 'age' => '18').errors
puts errors.to_h.inspect
# {
# :email => ["must be filled"],
# :age => ["must be greater than 18"]
# }
Params-specific value coercion is handled by the hash type from
dry-types. It is built automatically for you based on the type specs and used prior to applying the validation rules
Handling empty strings
Your schema will automatically coerce empty strings to nil or an empty array, provided that you allow a value to be nil:
schema = Dry::Schema.Params do
required(:email).filled(:string)
required(:age).maybe(:integer, gt?: 18)
required(:tags).maybe(:array)
end
result = schema.call('email' => 'jane@doe.org', 'age' => '', 'tags' => '')
puts result.to_h
# {:email=>'jane@doe.org', :age=>nil, :tags=>[]}