ParamChecker

ParamChecker is a small Ruby library for validating and casting string parameters. It is for example a handy way to check GET/POST params in Ruby On Rails.

Installation

gem install param_checker

or add ParamChecker to your Gemfile

gem 'param_checker'

and afterwards (when using the Gemfile) execute

bundle install

Usage

Include the ParamChecker module where ever you like. I usually put it into my Rails ApplicationController.rb

class ApplicationController < ActionController::Base
  include ParamChecker
end

You can then simply call for example check_string(params[:name], "Mia", :allowed => ["foo", "bar"]) in every controller.

Instead of including the module you could also call all functions of the module directly, like

ParamChecker.check_string(params[:name], "Mia", ["foo", "bar"])

There are currently 5 supported functions:

check_integer(param, default, options)
check_float(param, default, options)
check_string(param, default, options)
check_symbol(param, default, options)
check_boolean(param, default, options)

param is the string parameter to check.
default is the value that will be returned when param does not pass the check.
options are function specific options to check param against:
- :min, :max in check_integer and check_float are the minimum and maximum allowed values of param. (If not provided then no range is checked at all.)
- :allowed in check_string and check_symbol represent the allowed values of param. It can be either a regular expression, a string (resp. a symbol for check_symbol), or an array of strings (resp. an array of symbols for check_symbol).
- :true and :false represent the allowed string values for the true and false booleans. By default is :true => [“1”, “true”] and :false => [“0”, “false”]

All functions return the casted value (check_integer returns an integer, check_symbol returns a symbol, and so on).

Examples

Below are some simple examples how to use those functions.

# Check if per_page parameter is a valid integer representation, ensure that it is bigger than 1 and smaller than 100 and return its integer value. Otherwise return 10.
page = check_integer(params[:per_page], 10, :min => 1, :max => 100)

# If field parameter is equal to "name" or "address" then return it, otherwise return "name".
field = check_string(params[:field], "name", :allowed => ["name", "address"])

# Return the boolean if params[:accepted] is a valid boolean representation and the default false otherwise.
accepted = check_boolean(params[:accepted], false)

# Have custom boolean string representation values.
accepted = check_boolean(params[:accepted], false, :true => ["yep", "yes"], :false => ["nope", "no"])

Alternative usage

Since version 0.3 you can also extend your Hash or HashWithIndifferentAccess with ParamChecker::HashExt. This will allow you to directly call the ParamChecker methods on the params hash:

params.check(type, params_key, default, options)

type can be:

:i or :integer calls check_integer internally
:f or :float calls check_float internally
:s or :string calls check_string internally
:sym or :symbol calls check_symbol internally
:b or :boolean calls check boolean internally

params_key can be either an array of keys or just one key to access the hash.

Examples

# Checks params[:page] and returns the integer representation if valid.
params.check(:i, :page, 5, :min => 1)

# Check params[:company][:name] and returns "Comparilla" if invalid.
params.check(:s, [:company, :name], "Comparilla")

# Does exactly the same (alternative type symbol for string type)
params.check(:string, [:company, :name], "Comparilla")

Testing

ParamChecker uses RSpec for testing and has a rake task for executing the provided specs

rake spec