Rails and Databases

Rails
1

Hello,

I am new to RoR and have several questions.

  1. I have an existing DB and I want to develop an application that uses
    this
    existing DB. How do I import this DB into my application. What I mean
    is, I
    dont want to generate new models using rails, I want to use the existing
    DB.

  2. My DB contains tables named abc_profile, abc_friends and
    abc_register.
    One profile can have many friends and one profile can have one register.
    What I have done is, I used the generate model script to generate the 3
    models, and in the AbcProfile class, I wrote has_many :abc_friends and
    also
    wrote has_one :abc_register. In the AbcFriends class I wrote belongs_to
    :abc_profile, and in the AbcRegister class I also wrote belongs_to
    :abc_profile. Then I made a profile controller (generate controller
    Profile)
    and wrote in it @result = AbcProfile.find(:all).

In the app/views/profile/index.rhtml file, I wrote <% @result.each do
|res|
%>, but this line is giving an error. The error is

NoMethodError in Profile#index

Showing profile/index.rhtml where line #1 raised:

You have a nil object when you didn’t expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.each

Extracted source (around line #1):

1: <% @result.each do |res| %>
2:


3:
4:

Please help me with this error, and also guide me if I have done
anything
wrong in the above mentioned code. Also tell me about the table names
and
about the underscore in the table names, I mean do I write has_many
:abc_profile, or do I write has_many :AbcProfile.

Any help will be highly appreciated

Please reply to the email address [email protected]

–
Regards

Haris G.
2

Hello,

Am Montag, 31. Dezember 2007 schrieb Haris G.:

Hello,

I am new to RoR and have several questions.

  1. I have an existing DB and I want to develop an application that uses
    this existing DB. How do I import this DB into my application. What I mean
    is, I dont want to generate new models using rails, I want to use the
    existing DB.

If not set somewhere, models are more or less generated on the fly from
your
tables.

  1. My DB contains tables named abc_profile, abc_friends and abc_register.
    One profile can have many friends and one profile can have one register.
    What I have done is, I used the generate model script to generate the 3
    models, and in the AbcProfile class, I wrote has_many :abc_friends and also
    wrote has_one :abc_register. In the AbcFriends class I wrote belongs_to

If not set elsehwere, table-names ought to be plural. Have you set this
according to your needs?

:abc_profile, and in the AbcRegister class I also wrote belongs_to
:abc_profile. Then I made a profile controller (generate controller
: Profile)

and wrote in it @result = AbcProfile.find(:all).

In the app/views/profile/index.rhtml file, I wrote <% @result.each do |res|
%>, but this line is giving an error. The error is

NoMethodError in Profile#index

Seems your controller’s index-Method is not found - it’s hard to say
what went
wrong, if you don’t show your controller completely (pastie.caboo.se is
your
friend)

3:


4:

@results is nil (in Java Terms null) 'cause it hasn’t been definied,
'cause
your controller wasn’t executed.

Keep smiling
yanosz

3

thanx for your instant reply. Lemme send the code to you

I have only one controller file named “profile_controller.rb”, and it
contains

class ProfileController < ApplicationController
@result = MhpProfile.find(:all)
end

I have 3 Models

“mhp_friends.rb”, “mhp_profile.rb”, “mhp_register.rb”

class MhpFriends < ActiveRecord::Base
belongs_to :MhpProfile
def self.table_name() “mhp_friends” end
end

class MhpProfile < ActiveRecord::Base
has_many :MhpFriends
has_one :MhpRegister
def self.table_name() “mhp_profile” end
end

class MhpRegister < ActiveRecord::Base
belongs_to :MhpProfile
def self.table_name() “mhp_register” end
end

I hope this helps. I have only one view under
app/views/profile/index.rhtml,
and the first line it has is

<% @result.each do |res| %>

which gives an error.

Please help

On Dec 31, 2007 5:30 PM, Jan L. [email protected]
wrote:

mean

What I have done is, I used the generate model script to generate the 3

wrong, if you don’t show your controller completely (pastie.caboo.se is

yanosz

–
Regards

Haris G.

4

On Mon, 31 Dec 2007 16:42:53 +0500, Haris G. wrote:

  1. I have an existing DB and I want to develop an application that uses
    this existing DB. How do I import this DB into my application. What I
    mean is, I dont want to generate new models using rails, I want to use
    the existing DB.

here’s an example db which has been created by RoR:

thufir@arrakis ~/Desktop/strawr/db $
thufir@arrakis ~/Desktop/strawr/db $ sqlite3 development.sqlite3
SQLite version 3.4.1
Enter “.help” for instructions
sqlite> .schema
CREATE TABLE colors (“id” INTEGER PRIMARY KEY NOT NULL, “feed_id”
integer
DEFAULT NULL, “tag_id” integer DEFAULT NULL, “color” varchar(255)
DEFAULT
NULL);
CREATE TABLE feeds (“id” INTEGER PRIMARY KEY NOT NULL, “feed” varchar
(255) DEFAULT NULL);
CREATE TABLE schema_info (version integer);
CREATE TABLE tags (“id” INTEGER PRIMARY KEY NOT NULL, “tag” varchar(255)
DEFAULT NULL);
sqlite> .quit
thufir@arrakis ~/Desktop/strawr/db $

What does your schema look like? Probably you need to look into a
getting RoR to work with a legacy db, which is a hassle (at least for
me).

I don’t advise it until you’ve written at least one RoR app from the
ground up.

-Thufir

5

Thanx a lot Jan and Thufir for your help. But now Im getting another
error
(and a weird one too). The page doesnt display anything, but the server
console says

ERROR Errno::ENOBUFS: An operation on a socket could not be performed
because the system lacked sufficient buffer space or because a queue was
full.

Any insight into this error ??

On Dec 31, 2007 9:42 PM, Thufir [email protected] wrote:

here’s an example db which has been created by RoR:
(255) DEFAULT NULL);

I don’t advise it until you’ve written at least one RoR app from the
ground up.

-Thufir

–
Regards

Haris G.

6

Hello,

Am Dienstag, 1. Januar 2008 schrieb Haris G.:

Thanx a lot Jan and Thufir for your help. But now Im getting another error
(and a weird one too). The page doesnt display anything, but the server
console says

ERROR Errno::ENOBUFS: An operation on a socket could not be performed
because the system lacked sufficient buffer space or because a queue was
full.

Looks like the server has some trouble accessing your DB or processing
results.
Is your database queried?
Did you modify config/database.yml according to your needs?

Keep smiling
yanosz

7

Hello,

Am Montag, 31. Dezember 2007 schrieb Haris G.:

thanx for your instant reply. Lemme send the code to you

I have only one controller file named “profile_controller.rb”, and it
contains

class ProfileController < ApplicationController
@result = MhpProfile.find(:all)
end

ah, here we go:

controllers need methods for the actions they provide:
Here:

class ProfileController < ApplicationController
def index
@result = MhpProfile.find(:all)
end
end

I guess you should get yourself some kind of docs (books, howtos, etc)

Keep smiling
yanosz