Class: Assertion::Guard

Inherits:
Object
  • Object
show all
Extended by:
Attributes
Defined in:
lib/assertion/guard.rb

Overview

The base class for object guards

The guard defines a desired state for the object and checks if that state is valid.

Its ‘call` method either returns the guarded object, or (when its state is invalid) raises an exception

The class DSL also defines a ‘.[]` shortcut to initialize and call the guard for given object immediately.

Examples:

class AdultOnly < Assertion::Guard
  alias_method :user, :object

  def state
    IsAdult[user.attributes]
  end
end

jack = User.new name: "Jack", age: 10
john = User.new name: "John", age: 59

AdultOnly[jack]
# => #<Assertion::InvalidError @messages=["Jack is a child (age 10)"]>
AdultOnly[john]
# => #<User @name="John", @age=59>

Instance Attribute Summary collapse

Class Method Summary collapse

Methods included from Attributes

attribute, attributes

Instance Attribute Details

#object ⇒ Object (readonly)

Returns The object whose state should be tested.

Returns:

  • (Object) —

    The object whose state should be tested



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# File 'lib/assertion/guard.rb', line 63

def object
  @object
end

Class Method Details

.[](object) ⇒ Object

Initializes and guard for the provided object and calls it immediately

Parameters:

  • object (Object) —

    The object whose state should be tested



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# File 'lib/assertion/guard.rb', line 47

def [](object)
  new(object).call
end

.call ⇒ Object

Validates the state of the [#object] and returns valid object back

Returns:

  • (Object) —

    The object whose state should be tested

Raises:



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# File 'lib/assertion/guard.rb', line 86

def call
  state.validate!
  object
end

.initialize(object) ⇒ Object 



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# File 'lib/assertion/guard.rb', line 74

def initialize(object)
  @object = object
  self.class.attributes.each(&method(:__set_attribute__))
  freeze
end

.new(object) ⇒ Assertion::Guard

Creates the guard instance for the provided object

Parameters:

  • object (Object)

Returns:




# File 'lib/assertion/guard.rb', line 65