module Assertion

The module declares:

• assertions about objects

• guards (validations) for objects

@example Assertion

# config/locales/en.yml
# ---
# en:
#   assertion:
#     is_adult:
#       truthy: "%{name} is an adult (age %{age})"
#       falsey: "%{name} is a child (age %{age})"

IsAdult = Assertion.about :name, :age do
  age >= 18
end

joe = OpenStruct.new(name: 'Joe', age: 13)
IsAdult[joe.to_h].validate!
# => #<Assertion::InvalidError @messages=["Joe is a child (age 13)"]>

jane = OpenStruct.new(name: 'Jane', age: 22)
IsAdult.not[jane.to_h].validate!
# => #<Assertion::InvalidError @messages=["Jane is an adult (age 22)"]

@example Guard

AdultOnly = Assertion.guards :user do
  IsAdult[user.to_h]
end

AdultOnly[joe]
# => #<Assertion::InvalidError @messages=["Joe is a child (age 13)"]>
AdultOnly[jane]
# => #<OpenStruct @name="Jane", @age=22>

@api public