# Creating new object using params posted from form

**URL:** <https://www.ruby-forum.com/t/creating-new-object-using-params-posted-from-form/65700>\
**Category:** Rails\
**Created:** [February 11, 2006, 2:21am UTC](https://www.ruby-forum.com/t/creating-new-object-using-params-posted-from-form/65700 "2006-02-11T02:21:48Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![Iain\_Rose](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/7cd45c/32.png) [@Iain\_Rose](https://www.ruby-forum.com/u/Iain_Rose)\
**Post date:** [February 11, 2006, 2:21am UTC](https://www.ruby-forum.com/t/creating-new-object-using-params-posted-from-form/65700/1 "2006-02-11T02:21:48Z")

</div>

Hi,

I have a problem creating an new instance of an object using params  
posted  
from a form.

The object being created is not a sub class of ActiveRecord and is very  
simple. It’s model file is just:

class Search

attr\_accessor :major\_build\_id, :minor\_build\_id, :environment\_id,  
:system\_id

end

The controller creates an empty instance variable the first time the  
page is  
called, else it tries to populate it with the values of params from the  
form.

class ResultsController \< ApplicationController

def index  
list  
render :action =\> ‘list’  
end

def list  
if request.get?  
@search = Search.new  
else  
@search = Search.new(params[:search])  
end  
end

end

The form on the results/index page which populates the form posts back  
to  
itself and is also very simple

\<%= start\_form\_tag %\>

Major Build Name\<%= select :search, :major\_build\_id, [["Select", ""]]+@major\_builds %\>

Minor Build Name\<%= select :search, :minor\_build\_id, [["Select", ""]]+@minor\_builds %\>

Environment\<%= select :search, :environment\_id, [["Select", ""]]+@environments %\>

System\<%= select :search, :system\_id, [["Select", ""]]+@systems %\>

\<%= submit\_tag 'Update Results' %\>

\<%= end\_form\_tag %\>

The first time I call the page (using the GET request) is fine, but if I  
use  
the form to post any data I get an error.

ArgumentError in Results#index

wrong number of arguments (1 for 0)

RAILS\_ROOT: ./script/…/config/…  
Application Trace \<#\> | Framework Trace \<#\> | Full Trace \<#\>

#{RAILS\_ROOT}/app/controllers/results\_controller.rb:13:in `initialize' #{RAILS_ROOT}/app/controllers/results_controller.rb:13:in`new’  
#{RAILS\_ROOT}/app/controllers/results\_controller.rb:13:in `list' #{RAILS_ROOT}/app/controllers/results_controller.rb:4:in`index’  
-e:3:in `load’  
-e:3

c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action\_controller/base.rb:853:in  
`send' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/base.rb:853:in`perform\_action\_without\_filters’  
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action\_controller/filters.rb:332:in  
`perform_action_without_benchmark' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/benchmarking.rb:69:in`perform\_action\_without\_rescue’  
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action\_controller/benchmarking.rb:69:in  
`measure' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/benchmarking.rb:69:in`perform\_action\_without\_rescue’  
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action\_controller/rescue.rb:82:in  
`perform_action' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/base.rb:369:in`send’  
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action\_controller/base.rb:369:in  
`process_without_session_management_support' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/session_management.rb:116:in`process’  
c:/ruby/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/dispatcher.rb:38:in  
`dispatch' c:/ruby/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/webrick_server.rb:117:in`handle\_dispatch’  
c:/ruby/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/webrick\_server.rb:83:in  
`service' c:/ruby/lib/ruby/1.8/webrick/httpserver.rb:104:in`service’  
c:/ruby/lib/ruby/1.8/webrick/httpserver.rb:65:in `run' c:/ruby/lib/ruby/1.8/webrick/server.rb:155:in`start\_thread’  
c:/ruby/lib/ruby/1.8/webrick/server.rb:144:in `start' c:/ruby/lib/ruby/1.8/webrick/server.rb:144:in`start\_thread’  
c:/ruby/lib/ruby/1.8/webrick/server.rb:94:in `start' c:/ruby/lib/ruby/1.8/webrick/server.rb:89:in`each’  
c:/ruby/lib/ruby/1.8/webrick/server.rb:89:in `start' c:/ruby/lib/ruby/1.8/webrick/server.rb:79:in`start’  
c:/ruby/lib/ruby/1.8/webrick/server.rb:79:in `start' c:/ruby/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/webrick_server.rb:69:in`dispatch’  
c:/ruby/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/commands/servers/webrick.rb:59  
c:/ruby/lib/ruby/site\_ruby/1.8/rubygems/custom\_require.rb:18:in  
`require__' c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:18:in`require’  
c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.2.5/lib/active\_support/dependencies.rb:214:in  
`require' c:/ruby/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/commands/server.rb:28 c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:18:in`require\_\_’  
c:/ruby/lib/ruby/site\_ruby/1.8/rubygems/custom\_require.rb:18:in  
`require' c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.2.5/lib/active_support/dependencies.rb:214:in`require’  
./script/server:3

#{RAILS\_ROOT}/app/controllers/results\_controller.rb:13:in `initialize' #{RAILS_ROOT}/app/controllers/results_controller.rb:13:in`new’  
#{RAILS\_ROOT}/app/controllers/results\_controller.rb:13:in `list' #{RAILS_ROOT}/app/controllers/results_controller.rb:4:in`index’  
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action\_controller/base.rb:853:in  
`send' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/base.rb:853:in`perform\_action\_without\_filters’  
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action\_controller/filters.rb:332:in  
`perform_action_without_benchmark' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/benchmarking.rb:69:in`perform\_action\_without\_rescue’  
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action\_controller/benchmarking.rb:69:in  
`measure' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/benchmarking.rb:69:in`perform\_action\_without\_rescue’  
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action\_controller/rescue.rb:82:in  
`perform_action' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/base.rb:369:in`send’  
c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action\_controller/base.rb:369:in  
`process_without_session_management_support' c:/ruby/lib/ruby/gems/1.8/gems/actionpack-1.11.2/lib/action_controller/session_management.rb:116:in`process’  
c:/ruby/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/dispatcher.rb:38:in  
`dispatch' c:/ruby/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/webrick_server.rb:117:in`handle\_dispatch’  
c:/ruby/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/webrick\_server.rb:83:in  
`service' c:/ruby/lib/ruby/1.8/webrick/httpserver.rb:104:in`service’  
c:/ruby/lib/ruby/1.8/webrick/httpserver.rb:65:in `run' c:/ruby/lib/ruby/1.8/webrick/server.rb:155:in`start\_thread’  
c:/ruby/lib/ruby/1.8/webrick/server.rb:144:in `start' c:/ruby/lib/ruby/1.8/webrick/server.rb:144:in`start\_thread’  
c:/ruby/lib/ruby/1.8/webrick/server.rb:94:in `start' c:/ruby/lib/ruby/1.8/webrick/server.rb:89:in`each’  
c:/ruby/lib/ruby/1.8/webrick/server.rb:89:in `start' c:/ruby/lib/ruby/1.8/webrick/server.rb:79:in`start’  
c:/ruby/lib/ruby/1.8/webrick/server.rb:79:in `start' c:/ruby/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/webrick_server.rb:69:in`dispatch’  
c:/ruby/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/commands/servers/webrick.rb:59  
c:/ruby/lib/ruby/site\_ruby/1.8/rubygems/custom\_require.rb:18:in  
`require__' c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:18:in`require’  
c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.2.5/lib/active\_support/dependencies.rb:214:in  
`require' c:/ruby/lib/ruby/gems/1.8/gems/rails-1.0.0/lib/commands/server.rb:28 c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:18:in`require\_\_’  
c:/ruby/lib/ruby/site\_ruby/1.8/rubygems/custom\_require.rb:18:in  
`require' c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.2.5/lib/active_support/dependencies.rb:214:in`require’  
./script/server:3  
-e:3:in `load’  
-e:3

Request

_Parameters_: {“search”=\>{“minor\_build\_id”=\>"", “major\_build\_id”=\>"",  
“system\_id”=\>“1”, “environment\_id”=\>""}, “commit”=\>“Update Results”}

However I’ve found that if I update the “list” action in the results  
controller to this longer and uglier version, it works.

def list  
@search = Search.new  
if request.post?  
@search.major\_build\_id = params[:search][“major\_build\_id”].to\_i()  
@search.minor\_build\_id = params[:search][“minor\_build\_id”].to\_i()  
@search.environment\_id = params[:search][“environment\_id”].to\_i()  
@search.system\_id = params[:search][“system\_id”].to\_i()  
end  
end

This seems a bit long winded and I’m sure there is a simpler and more  
elegant way. Is there something I’m missing?

thanks

Iain

---

<div class="post-metadata">

**Author:** ![Iain\_Rose](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/7cd45c/32.png) [@Iain\_Rose](https://www.ruby-forum.com/u/Iain_Rose)\
**Post date:** [February 11, 2006, 2:46am UTC](https://www.ruby-forum.com/t/creating-new-object-using-params-posted-from-form/65700/2 "2006-02-11T02:46:35Z")

</div>

Hi –

On Fri, 10 Feb 2006, Iain Rose wrote:

> else  
> @search = Search.new(params[:search])

What you’ve done is equivalent to:

class C  
end

c = C.new(“arg”) # wrong # of arguments: 1 for 0

You’d need to write an initialize method – for example

class C  
def initialize(\*x) # optional argument x  
# do whatever here  
end  
end

Similarly, in your Search class, you would need to define initialize,  
probably to handle an optional argument (since it looks like you want  
to be able to call it with or without).

> ```
> @search.minor_build_id = params[:search]["minor_build_id"].to_i()
> @search.environment_id = params[:search]["environment_id"].to_i()
> @search.system_id = params[:search]["system_id"].to_i()
> 
> ```
> 
> end  
> end
> 
> This seems a bit long winded and I’m sure there is a simpler and more  
> elegant way. Is there something I’m missing?

If you do something like this in the Search class:

class Search  
attr\_accessor :major\_build\_id, :minor\_build\_id,  
:environment\_id, :system\_id

```
 def initialize(*search_hash)
   if search_hash
     search_hash.each do |key,value|
       send("#{key}=", value) # This calls the appropriate
                               # writer method, matching the key
     end
   end
 end

```

end

then you could do:

@search = Search.new(params[:search])

and/or

@search = Search.new

in the controller, depending on conditions, etc.

(It seems a bit anomalous to have this Search class among the models,  
but that’s another matter 🙂

David

–  
David A. Black (removed\_email\_address@domain.invalid)  
Ruby Power and Light ([http://www.rubypowerandlight.com](http://www.rubypowerandlight.com))

“Ruby for Rails” chapters now available  
from Manning Early Access Program! [Ruby for Rails](http://www.manning.com/books/black)

---

<div class="post-metadata">

**Author:** ![Iain\_Rose](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/7cd45c/32.png) [@Iain\_Rose](https://www.ruby-forum.com/u/Iain_Rose)\
**Post date:** [February 11, 2006, 6:31am UTC](https://www.ruby-forum.com/t/creating-new-object-using-params-posted-from-form/65700/3 "2006-02-11T06:31:11Z")

</div>

Thanks for the advice.

Can I ask why you don’t need to do this when using models that exist in  
the  
db. For example, when I use the scaffold generator to create a model  
called  
Search in a controller called Results, I get this in the controller …

class ResultsController \< ApplicationController  
…  
def create  
@search = Search.new(params[:search])  
if @search.save  
flash[:notice] = ‘Search was successfully created.’  
redirect\_to :action =\> ‘list’  
else  
render :action =\> ‘new’  
end  
end

I’m not intending to use scaffolding throughout my app but it proves it  
can  
work out of the box (sometimes). The class definition of the Search  
model  
doesn’t have an initialize method. Does it just inherit something  
simliar to  
your suggestion from it’s super class?

Also, as this is my first attempt at a Rails app (I’m branching out on  
my  
own after working through the agile book), can you explain what you mean  
by  
…

It seems a bit anomalous to have this Search class among the models

I’d like to start on the right tracks and not get into bad habits.

Thanks again for the advice.

Iain

---

<div class="post-metadata">

**Author:** ![Iain\_Rose](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/7cd45c/32.png) [@Iain\_Rose](https://www.ruby-forum.com/u/Iain_Rose)\
**Post date:** [February 11, 2006, 10:32pm UTC](https://www.ruby-forum.com/t/creating-new-object-using-params-posted-from-form/65700/4 "2006-02-11T22:32:53Z")

</div>

David is right. The scaffolding code is like that because it expects  
Search to be an ActiveRecord subclass. It’s ActiveRecord that  
provides the ability to call new with a hash. If you’re not  
subclassing ActiveRecord, you need to implement that yourself.

Cheers,

Pete Y.