# Check if a field exists
#
# ~~~
# var json1 = """{ "field1": "", "field2": "foo", "field3": 10, "field4": [] }"""
# var json2 = """{ "field1": "", "field2": "foo", "field3": 10 }"""
# var json3 = """{ "field1": "", "field2": "foo" }"""
#
# var validator = new ObjectValidator
# validator.add new RequiredField("field1")
# validator.add new RequiredField("field2")
# validator.add new RequiredField("field3")
# validator.add new RequiredField("field4", required=false)
#
# assert validator.validate(json1)
# assert validator.validate(json2)
# assert not validator.validate(json3)
# assert validator.validation.error("field3") == ["Required field"]
# ~~~
class RequiredField
	super FieldValidator

	# Is this field required?
	var required: nullable Bool

	redef fun validate_field(v, obj) do
		var required = self.required
		if (required != null and required or required == null) and not obj.has_key(field) then
			v.validation.add_error(field, "Required field")
			return false
		end
		return true
	end
end