Class: Hanami::Entity

Inherits:
Object
  • Object
show all
Defined in:
lib/hanami/entity.rb,
lib/hanami/entity/schema.rb

Overview

An object that is defined by its identity. See “Domain Driven Design” by Eric Evans.

An entity is the core of an application, where the part of the domain logic is implemented. It’s a small, cohesive object that expresses coherent and meaningful behaviors.

It deals with one and only one responsibility that is pertinent to the domain of the application, without caring about details such as persistence or validations.

This simplicity of design allows developers to focus on behaviors, or message passing if you will, which is the quintessence of Object Oriented Programming.

If we expand the code above in **pure Ruby**, it would be:

Hanami::Model ships ‘Hanami::Entity` for developers’s convenience.

Hanami::Model depends on a narrow and well-defined interface for an Entity - ‘#id`, `#id=`, `#initialize(attributes={})`.If your object implements that interface then that object can be used as an Entity in the Hanami::Model framework.

However, we suggest to implement this interface by including ‘Hanami::Entity`, in case that future versions of the framework will expand it.

See Dependency Inversion Principle for more on interfaces.

Examples:

With Hanami::Entity

require 'hanami/model'

class Person
  include Hanami::Entity
end

Pure Ruby

class Person
  attr_accessor :id, :name, :age

  def initialize(attributes = {})
    @id, @name, @age = attributes.values_at(:id, :name, :age)
  end
end

See Also:

Since:

  • 0.1.0

Defined Under Namespace

Modules: ClassMethods, Types Classes: Schema

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(attributes = nil) ⇒ Hanami::Entity

Instantiate a new entity

Parameters:

  • attributes (Hash, #to_h, NilClass) (defaults to: nil) —

    data to initialize the entity

Raises:

  • (TypeError) —

    if the given attributes are invalid

Since:

  • 0.1.0



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# File 'lib/hanami/entity.rb', line 123

def initialize(attributes = nil)
  @attributes = self.class.schema[attributes]
  freeze
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(m) ⇒ Object

Handle dynamic accessors

If internal attributes set has the requested key, it returns the linked value, otherwise it raises a NoMethodError

Since:

  • 0.7.0



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# File 'lib/hanami/entity.rb', line 143

def method_missing(m, *)
  attribute?(m) or super # rubocop:disable Style/AndOr
  attributes.fetch(m, nil)
end

Class Method Details

.inherited(klass) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Since:

  • 0.7.0



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# File 'lib/hanami/entity.rb', line 107

def self.inherited(klass)
  klass.class_eval do
    @schema = Schema.new
    extend  ClassMethods
  end
end

Instance Method Details

#==(other) ⇒ FalseClass, TrueClass

Implement generic equality for entities

Two entities are equal if they are instances of the same class and they have the same id.

Parameters:

  • other (Object) —

    the object of comparison

Returns:

  • (FalseClass, TrueClass) —

    the result of the check

Since:

  • 0.1.0



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# File 'lib/hanami/entity.rb', line 158

def ==(other)
  self.class == other.class &&
    id == other.id
end

#freeze ⇒ Object

Freeze the entity

Since:

  • 0.7.0



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# File 'lib/hanami/entity.rb', line 175

def freeze
  attributes.freeze
  super
end

#hash ⇒ Integer

Implement predictable hashing for hash equality

Returns:

  • (Integer) —

    the object hash

Since:

  • 0.7.0



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# File 'lib/hanami/entity.rb', line 168

def hash
  [self.class, id].hash
end

#id ⇒ Object, NilClass

Entity ID

Returns:

  • (Object, NilClass) —

    the ID, if present

Since:

  • 0.7.0



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# File 'lib/hanami/entity.rb', line 133

def id
  attributes.fetch(:id, nil)
end

#to_h ⇒ Hash Also known as: to_hash

Serialize entity to a Hash

Returns:

  • (Hash) —

    the result of serialization

Since:

  • 0.1.0



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# File 'lib/hanami/entity.rb', line 185

def to_h
  attributes.deep_dup.to_h
end