Validation in Azu is support by the Schema shards and is already included with every Crystal Application
Self validating Schemas are beneficial, and in my opinion, ideal, for when defining API Requests, Web Forms, JSON. Schema-Validation Takes a different approach and focuses a lot on explicitness, clarity, and precision of validation logic. It is designed to work with any data input, whether it’s a simple hash, an array or a complex object with deeply nested data.
Each validation is encapsulated by a simple, stateless predicate that receives some input and returns either true or false. Those predicates are encapsulated by rules which can be composed together using predicate logic, meaning you can use the familiar logic operators to build up a validation schema.
You can also perform validations for existing objects without the use of Schemas.
class User < Model
include Schema::Validation
property email : String
property name : String
property age : Int32
property alive : Bool
property childrens : Array(String)
property childrens_ages : Array(Int32)
# To use a custom validator. UniqueRecordValidator will be initialized with an `User` instance
use UniqueRecordValidator
# Use the `custom` class name predicate as follow
validate email, match: /\w+@\w+\.\w{2,3}/, message: "Email must be valid!", unique_record: true
validate name, size: (1..20)
validate age, gte: 18, lte: 25, message: "Must be 24 and 30 years old"
validate alive, eq: true
# Define your custom predicates
predicates do
def some?(value : String, some) : Bool
(!value.nil? && value != "") && !some.nil?
end
def if?(value : Array(Int32), bool : Bool) : Bool
!bool
end
end
def initialize(@email, @name, @age, @alive, @childrens, @childrens_ages)
end
end
Custom Validations
Simply create a class {Name}Validator with the following signature:
class EmailValidator < Schema::Validator
getter :record, :field, :message
def initialize(@record : UserModel)
@field = :email
@message = "Email must be valid!"
end
def valid? : Array(Schema::Error)
[] of Schema::Error
end
end
class UniqueRecordValidator < Schema::Validator
getter :record, :field, :message
def initialize(@record : UserModel)
@field = :email
@message = "Record must be unique!"
end
def valid? : Array(Schema::Error)
[] of Schema::Error
end
end
Defining Predicates
You can define your custom predicates by simply creating a custom validator or creating methods in the Schema::Predicates module ending with ? and it should return a boolean. For example:
class User < Model
property email : String
property name : String
property age : Int32
property alive : Bool
property childrens : Array(String)
property childrens_ages : Array(Int32)
...
# Uses a `presense` predicate
validate password : String, presence: true
# Use the `predicates` macro to define predicate methods
predicates do
# Presence Predicate Definition
def presence?(password : String, _other : String) : Bool
!value.nil?
end
end
def initialize(@email, @name, @age, @alive, @childrens, @childrens_ages)
end
end
Differences: Custom Validator vs Predicates
The differences between a custom validator and a method predicate are:
Custom Validators
Must be inherited from Schema::Validator abstract
Receives an instance of the object as a record instance var.
Must have a :field and :message defined.
Must implement a def valid? : Array(Schema::Error) method.
Predicates
Assertions of the property value against an expected value.
Predicates are light weight boolean methods.
Predicates methods must be defined as def {predicate}?(property_value, expected_value) : Bool .
Built in Predicates
These are the current available predicates.
gte - Greater Than or Equal To
lte - Less Than or Equal To
gt - Greater Than
lt - Less Than
size - Size
in - Inclusion
regex - Regular Expression
eq - Equal
Additional Parameters
message - Error message to display
nilable - Allow nil, true or false
