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 http://github.com/farrel/simplecheck.
## 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](
https://en.wikipedia.org/wiki/Point_in_polygon), 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
* Git repository - http://github.com/farrel/simplecheck]
* Rubygem page - http://rubygems.org/gems/simplecheck
## License
Simplecheck is released under the BSD License.
Copyright 2013 AIMRED CC. All rights reserved.
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