params code

Testing for nil or empty params in Ruby on Rails

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.

to ruby rails nil params by galatians on Apr 28, 2008 2 Comments

Unify the handling of XML records

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 = "<method name='delete'><params><param var='id' val='17648' /></params></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.

to ruby rexml cgi method params by jrobertson on Dec 02, 2007

Hash Tricks

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

to ruby rails hash params by MattScilipoti on Jun 12, 2006 2 Comments

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Testing for nil or empty params in Ruby on Rails

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