DZone Snippets: params code

Testing for nil or empty params in Ruby on Rails

galatians (Jonathan) — Mon, 28 Apr 2008 20:00:11 GMT

I find myself doing these 4 things a lot:



if params[:object] && !params[:object].empty

if params[:object] && params[:object] == value

if params[:object][:attribute] && !params[:object][:attribute].empty

if params[:object][:attribute] && params[:object][:attribute] == value

I put params_check() in my application.rb and it allows me to do this instead:



if params_check(:object)

if params_check(:object, value)

if params_check([:object, :attribute])

if params_check([:object, :attribute], value)



  def params_check(*args)

    if args.length == 1

      if args[0].class == Array

        if params[args[0][0]][args[0][1]] && !params[args[0][0]][args[0][1]].empty?

          true

        end

      else        

        if params[args[0]] && !params[args[0]].empty?

          true

        end

      end

    elsif args.length == 2

      if args[0].class == Array

        if params[args[0][0]][args[0][1]] && params[args[0][0]][args[0][1]] == args[1]

          true

        end

      else

        if params[args[0]] && params[args[0]] == args[1]

          true

        end

      end  

    end

  end

I stole this off another snippet and modified it to add more conditions. Thanks to whoever it was.

Unify the handling of XML records

jrobertson (James Robertson) — Sun, 02 Dec 2007 13:50:18 GMT

This Ruby code creates, updates or deletes an XML record, using a hash, record handling objects, and XML to invoke the correct method.



#file: recordx_handler.rb

require 'recordx'



class RecordX_Update < RecordX

  def call(params)

    #todo: write the code to read the xml parameter string

    update_record(h)

    save_file 

  end

end



class RecordX_Create < RecordX

  def call(params)

    #todo: write the code to read the xml parameter string  

    create_record(h)

  end

end



class RecordX_Delete < RecordX

  def call(params)

    doc = Document.new(params)

    node = doc.root.elements["param[@var='id']"]

    puts node

    id = node.attributes.get_attribute('val').to_s

    delete_record(id)

    puts 'deleted record ' + id

    save_file

  end

end



class RecordX_handler

  def invoke(method, params)

    h = Hash.new

    h["create"] = RecordX_Create.new

    h["update"] = RecordX_Update.new

    h["delete"] = RecordX_Delete.new

    h[method].call(params)

  end

end



if __FILE__ == $0

  xml_method = ""

  doc = Document.new(xml_method)

  method = doc.root.attributes.get_attribute('name').to_s

  params = doc.root.elements['params'].to_s



  rh = RecordX_handler.new

  rh.invoke(method, params)

end

This code is intended to be called by a Ruby CGI script which can simply relay the cgi post argument to the recordx_handler object.

Hash Tricks

MattScilipoti (Matt Scilipoti) — Tue, 13 Jun 2006 02:17:54 GMT

From: http://blog.caboo.se/articles/2006/06/11/stupid-hash-tricks



class Hash



  # lets through the keys in the argument

  # >> {:one => 1, :two => 2, :three => 3}.pass(:one)

  # => {:one=>1}

  def pass(*keys)

    tmp = self.clone

    tmp.delete_if {|k,v| ! keys.include?(k) }

    tmp

  end



  # blocks the keys in the arguments

  # >> {:one => 1, :two => 2, :three => 3}.block(:one)

  # => {:two=>2, :three=>3}

  def block(*keys)

    tmp = self.clone

    tmp.delete_if {|k,v| keys.include?(k) }

    tmp

  end



end

In case you don’t already see the utility of this:



def some_action

    # some script kiddie also passed in :bee, which we don't want tampered with _here_.

    @model = Model.create(params.pass(:foo, :bar))

  end

or those cases where you don’t want to let everything through and don’t want to resort to attr_protected or attr_accessible