Simplecheck 1.0

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

If a check fails a Simplecheck::CheckFailed exception is raised.

Installation

Simplecheck is available as a Rubygem installable via gem install
simplecheck].

A git repository is also available at
GitHub - farrel/simplecheck: Simplecheck is a lightweight property checking API for Ruby designed to quickly check arguments in under 50 lines of Ruby. Once included into a class it provides the check instance method which takes arguments and a condition to check them against..

Usage

require 'simplecheck'

class Customer
  include Simplecheck

  attr_accessor( :name, :age )

  def initialize( name, age )
    check( name, String ) # Check name is String
    check( age, 18..75 )  # Check age is within Range

    @name, @age = name, age
  end
end

Customer.new( "Joe", 25 ) # No error
Customer.new( nil, 25 )   rescue puts "Name can not be nil"
Customer.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.

def calculate_percentage( score, total )
  check( total > 0 )
  100.0 * score / total
end

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.

def greatest_common_divisor( a, b )
  check( a, b, Integer )
  # GCD Algorithm...
end

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.

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 , ->(p){ !Dict.lookup( p )})

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.odd?
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:

check( i, j, k, Integer )
check( a, b, c ) do |n|
  n.even?
end

Resources

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.

THIS SOFTWARE IS PROVIDED BY AIMRED CC “AS IS” AND ANY EXPRESS OR
IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
NO
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