Simplecheck

Simplecheck is a property checking API for Ruby designed for quickly checking arguments. Once included into a class it provides the check instance method which takes a list of arguments and a condition to check them against.

If a check fails an exception of type Simplecheck::CheckFailed is raised.

Usage

require 'simplecheck'

class Person
  include Simplecheck

  def initialize( name, age )
    check( name )         # Check name is not nil
    check( age, 18..75 )  # Check age is within range

    @name = name
    @age = age
  end
end

Person.new( "Joe", 25 ) # No error
Person.new( nil, 25 )   rescue puts "Name can not be nil"
Person.new( "Joe", 15 ) rescue puts "Age is out of range"

Check Methods

Simplecheck currently supports three different check methods:

  • Expression Check
  • Case Equality (===) Check
  • Block Check

Expression Check

In the simplest case check takes an expression as an argument. If the expression evaluates to nil or false it will fail.

check( a > 2 )

Case Equality (===) Check

If two or more arguments are given without a block, then the last argument becomes the condition against which the previous arguments are checked. To accomplish this the condition argument should implement the case equality operator (=== or threequal) in a logical manner.

If a class does not alias or implement it's own version of === it has the same functionality as ==. The following Ruby Core classes already alias === to various instance methods. If a class does not alias or implement it's own version of === it has the same functionality as ==.

Class

=== is aliased to kind_of?:

check( age, Numeric )

Range

=== is aliased to include?:

check( age, 18..75 )

Regexp

=== is aliased to match:

check( phone_number, /^\d\d\d-\d\d\d\d$/ )

Proc

=== is aliased to call: 

check( password, password_confirmation, lambda{ |pwd| !Dictionary.check( pwd )})

Custom Check Object

The default behaviour of Object#=== is the same as Object#==. To customise the behaviour implement your own Object#=== method.

For example to check whether a set of points is inside a given polygon we would implement Polygon#=== as a point-in-polygon algorithm, allowing us to carry out the check using a Polygon instance:

check( point_1, point_2, polygon )

Block Check

A block can be passed to check, with the arguments passed to check then passed individually to the block:

check( a, b, c ) do |n|
  n.modulo?(2).zero?
end

This is syntactic sugar for the Proc Case Equality check.

Multiple Arguments

Case Equality and Block checks can be called with multiple arguments, with each argument being checked individually against the condition:

License

Simplecheck is released under the BSD License.

Copyright 2013 AIMRED CC. All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

  2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

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