Schemas come to solve a simple problem. Sometimes we would like to have type-safe guarantee parameters when parsing HTTP requests or Hash(String, String) for a request. Schema shard resolve precisely this problem with the added benefit of enabling self validating schemas that can be applied to any object, requiring little to no boilerplate code making you more productive from the moment you use this shard.
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.
Add this to your application's shard.yml:
dependencies:
schema:
github: azutoolkit/schemarequire "schema"Schemas are defined as value objects, meaning structs, which are NOT mutable, making them ideal to pass schema objects as arguments to constructors.
class Example
include Schema::Definition
include Schema::Validation
property email : String
property name : String
property age : Int32
property alive : Bool
property childrens : Array(String)
property childrens_ages : Array(Int32)
property last_name : String
use EmailValidator, UniqueRecordValidator
validate :email, match: /\w+@\w+\.\w{2,3}/, message: "Email must be valid!"
validate :name, size: (1..20)
validate :age, gte: 18, lte: 25, message: "Age must be 18 and 25 years old"
validate :alive, eq: true
validate :last_name, presence: true, message: "Last name is invalid"
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, @last_name)
end
endExample.from_json
Example.from_urlencoded("&foo=bar")
# Any object that responds to `.each`, `#[]?`, `#[]`, `#fetch_all?`
Example.new(params)valid? - Bool
validate! - True or Raise ValidationError
errors - Errors(T, S)Below find a list of the supported params parsing structure and it's corresponding representation in Query String or application/x-www-form-urlencoded form data.
http_params = HTTP::Params.build do |p|
p.add("string", "string_value")
p.add("optional_string", "optional_string_value")
p.add("string_with_default", "string_with_default_value")
p.add("int", "1")
p.add("optional_int", "2")
p.add("int_with_default", "3")
p.add("enum", "Foo")
p.add("optional_enum", "Bar")
p.add("enum_with_default", "Baz")
p.add("array[]", "foo")
p.add("array[]", "bar")
p.add("array[]", "baz")
p.add("optional_array[]", "foo")
p.add("optional_array[]", "bar")
p.add("array_with_default[]", "foo")
p.add("hash[foo]", "1")
p.add("hash[bar]", "2")
p.add("optional_hash[foo][]", "3")
p.add("optional_hash[foo][]", "4")
p.add("optional_hash[bar][]", "5")
p.add("hash_with_default[foo]", "5")
p.add("tuple[]", "foo")
p.add("tuple[]", "2")
p.add("tuple[]", "3.5")
p.add("boolean", "1")
p.add("optional_boolean", "false")
p.add("boolean_with_default", "true")
p.add("nested[foo]", "1")
p.add("nested[bar]", "3")
p.add("nested[baz][]", "foo")
p.add("nested[baz][]", "bar")
endparams = HTTP::Params.parse("email=test%40example.com&name=john&age=24&alive=true&childrens%5B%5D=Child1%2CChild2&childrens_ages%5B%5D=12&childrens_ages%5B%5D=18&address%5Bcity%5D=NY&address%5Bstreet%5D=Sleepy+Hollow&address%5Bzip%5D=12345&address%5Blocation%5D%5Blongitude%5D=41.085651&address%5Blocation%5D%5Blatitude%5D=-73.858467&address%5Blocation%5D%5Buseful%5D=true")
# HTTP::Params responds to `#[]`, `#[]?`, `#fetch_all?` and `.each`
subject = ExampleController.new(params)Accessing the generated schemas:
user = subject.user - Example
address = user.address - Example::Address
location = address.location - Example::Address::Locationjson = %({ "user": {
"email": "[email protected]",
"name": "Fake name",
"age": 25,
"alive": true,
"childrens": ["Child 1", "Child 2"],
"childrens_ages": [9, 12]
}})
user = Example.from_json(json, "user")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
def initialize(@email, @name, @age, @alive, @childrens, @childrens_ages)
end
endSimply 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
endYou 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
endThe differences between a custom validator and a method predicate are:
Custom Validators
- Must be inherited from
Schema::Validatorabstract - Receives an instance of the object as a
recordinstance var. - Must have a
:fieldand:messagedefined. - 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.
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 - EqualCONTRIBUTE - Add more predicates to this shards by contributing a Pull Request.
Additional params
message - Error message to display
nilable - Allow nil, true or false- Fork it (https://github.com/your-github-user/schemas/fork)
- Create your feature branch (
git checkout -b my-new-feature) - Commit your changes (
git commit -am 'Add some feature') - Push to the branch (
git push origin my-new-feature) - Create a new Pull Request
- @eliasjpr Elias J. Perez - creator, maintainer
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