Rails - Dec 2005 - myObject.send(column.name) from Agile Development book

I''m studying the Agile Development with Rails book.  In the chapter
that
first sets up the depot application (page 68), there is this bit of code
from a view:

<% for product in @products %>
  <tr>
  <% for column in Product.content_columns %>
    <td><%=h product.send(column.name) %></td>
  <% end %>
 etc...

I am trying to absorb both Ruby and rails as fast as I can.  So I am
searching both the Ruby API and the Rails API for methods that I don''t
know.  When I lookup "send" in the rails API, I don''t find
anything.  When I
look it up in the Ruby API, it says that the form is obj.send(symbol
[,args...]).  Well, there is no symbol in use here.  So I am confused about
the "send".

Then, I can''t find a method "name" anywhere.  Unlike
"human_name", it is not
listed as one of the methods of a Column in active record. At least I
can''t
find it.

I know what this code accomplishes, but I wish I understood it better.

Can anyone point me in the right direction?
Thanks,
Shelby


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I suggest that you use script/console and irb to find stuff that isn''t
in the
docs.

First go to the directory of your rails app, and do the following:

fg@moo:/opt/www/mart$ script/console
Loading development environment.
>> Product.columns[1].name
=> "product_category_id"
>> Product.columns[2].name
=> "reference"
>> Product.columns[2].name.class
=> String
>> Product.columns[2].methods.sort
=> ["==", "===", "=~", "__id__",
"__send__", "`", "b64encode", "blank?",
"class", "clone", "dclone", "decode64",
"decode_b", "default", "display",
"dup", "encode64", "eql?", "equal?",
"extend", "freeze", "frozen?", "hash",
"human_name", "id", "inspect",
"instance_eval", "instance_of?",
"instance_variable_get", "instance_variable_set",
"instance_variables",
"is_a?", "kind_of?", "klass", "limit",
"load", "method", "methods", "name",
"nil?", "null", "number?", "object_id",
"primary", "primary=",
"private_methods", "protected_methods",
"public_methods",
"remove_subclasses_of", "require", "require_gem",
"require_gem_with_options",
"require_library_or_gem", "respond_to?",
"returning", "send",
"silence_stderr", "silence_warnings",
"singleton_methods", "subclasses_of",
"suppress", "taguri", "taguri=",
"taint", "tainted?", "text?", "to_a",
"to_s", "to_yaml", "to_yaml_properties",
"to_yaml_style", "type",
"type_cast", "type_cast_code", "untaint"]

So there''s a ''name'' method which gives you the name
of the column.

fg@moo:/opt/www/mart$ irb
irb(main):001:0> 5.send(:+, 4)
=> 9
irb(main):002:0> 5.send("+", 4)
=> 9

5 is an object, that has a method "+" and accept another object to add
it.
Looks like ''send'' method accepts either a symbol like :+ or a
string "+" to
name the method.

Good luck,

Francois

On Tuesday 27 December 2005 11:22, Shelby Westman wrote:
> I''m studying the Agile Development with Rails book.  In the
chapter that
> first sets up the depot application (page 68), there is this bit of code
> from a view:
>
> <% for product in @products %>
>   <tr>
>   <% for column in Product.content_columns %>
>     <td><%=h product.send(column.name) %></td>
>   <% end %>
>  etc...
>
> I am trying to absorb both Ruby and rails as fast as I can.  So I am
> searching both the Ruby API and the Rails API for methods that I
don''t
> know.  When I lookup "send" in the rails API, I don''t
find anything.  When
> I look it up in the Ruby API, it says that the form is obj.send(symbol
> [,args...]).  Well, there is no symbol in use here.  So I am confused about
> the "send".
>
> Then, I can''t find a method "name" anywhere.  Unlike
"human_name", it is
> not listed as one of the methods of a Column in active record. At least I
> can''t find it.
>
> I know what this code accomplishes, but I wish I understood it better.
>
> Can anyone point me in the right direction?
> Thanks,
> Shelby

You found the right send method.  The first argument to send is the  
name of the method that you''d like to invoke, followed by any  
arguments needed by the method.

http://www.ruby-doc.org/core/classes/Object.html#M001048

Regarding name, it is an attribute of Column, as is default, limit, etc.

http://api.rubyonrails.com/classes/ActiveRecord/ConnectionAdapters/ 
Column.html

In the case of the depot app, that would be product.
On Dec 26, 2005, at 10:22 PM, Shelby Westman wrote:
> I''m studying the Agile Development with Rails book.  In the
chapter
> that first sets up the depot application (page 68), there is this  
> bit of code from a view:
>
> <% for product in @products %>
>   <tr>
>   <% for column in Product.content_columns %>
>     <td><%=h product.send(column.name) %></td>
>   <% end %>
>  etc...
>
> I am trying to absorb both Ruby and rails as fast as I can.  So I  
> am searching both the Ruby API and the Rails API for methods that I  
> don''t know.  When I lookup "send" in the rails API, I
don''t find
> anything.  When I look it up in the Ruby API, it says that the form  
> is obj.send(symbol [,args...]).  Well, there is no symbol in use  
> here.  So I am confused about the "send".
>
> Then, I can''t find a method "name" anywhere.  Unlike
"human_name",
> it is not listed as one of the methods of a Column in active  
> record. At least I can''t find it.
>
> I know what this code accomplishes, but I wish I understood it better.
>
> Can anyone point me in the right direction?
> Thanks,
> Shelby
>
>
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails


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Disregard the last sentence below.  It was extraneous.

I had started to say "in the case of the depot app the names of the  
methods would be product.title, product.description, etc.


On Dec 27, 2005, at 12:01 AM, Steven Smith wrote:
> You found the right send method.  The first argument to send is the  
> name of the method that you''d like to invoke, followed by any  
> arguments needed by the method.
>
> http://www.ruby-doc.org/core/classes/Object.html#M001048
>
> Regarding name, it is an attribute of Column, as is default, limit,  
> etc.
>
> http://api.rubyonrails.com/classes/ActiveRecord/ConnectionAdapters/ 
> Column.html
>
> In the case of the depot app, that would be product.
> On Dec 26, 2005, at 10:22 PM, Shelby Westman wrote:
>
>> I''m studying the Agile Development with Rails book.  In the  
>> chapter that first sets up the depot application (page 68), there  
>> is this bit of code from a view:
>>
>> <% for product in @products %>
>>   <tr>
>>   <% for column in Product.content_columns %>
>>     <td><%=h product.send(column.name) %></td>
>>   <% end %>
>>  etc...
>>
>> I am trying to absorb both Ruby and rails as fast as I can.  So I  
>> am searching both the Ruby API and the Rails API for methods that  
>> I don''t know.  When I lookup "send" in the rails
API, I don''t find
>> anything.  When I look it up in the Ruby API, it says that the  
>> form is obj.send(symbol [,args...]).  Well, there is no symbol in  
>> use here.  So I am confused about the "send".
>>
>> Then, I can''t find a method "name" anywhere.  Unlike
"human_name",
>> it is not listed as one of the methods of a Column in active  
>> record. At least I can''t find it.
>>
>> I know what this code accomplishes, but I wish I understood it  
>> better.
>>
>> Can anyone point me in the right direction?
>> Thanks,
>> Shelby
>>
>>
>> _______________________________________________
>> Rails mailing list
>> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
>> http://lists.rubyonrails.org/mailman/listinfo/rails
>
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails


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