Rails and Databases

rubyonrails-talk
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: <table width="100%" border="0" cellspacing="0" cellpadding="0">
3: <tr>
4: <td valign="top">

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 harisgulzar@gmail.com

2

Hello,

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.

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

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)

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: <table width="100%" border="0" cellspacing="0" cellpadding="0"> 3: <tr> 4: <td valign="top">

@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

4

Hello,

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

5

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

.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);

.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

6

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 ??

7

Hello,