Single Table Inheritance implementation

rubyonrails-talk
1

I want to change the "type" field for a table but am getting an error: read_creatures.rb:19: undefined local variable or method `green_dragon'

I've tried both "green_dragon" and the class name "GreenDragon" with both giving (different) errors :frowning:

thufir@arrakis ~/Desktop/dwemthys $ thufir@arrakis ~/Desktop/dwemthys $ ruby make_creatures.rb -- create_table(:creatures)   SQL (0.023529) CREATE TABLE creatures ("id" INTEGER PRIMARY KEY NOT NULL, "type" varchar(255) DEFAULT NULL, "life" integer DEFAULT NULL, "strength" integer DEFAULT NULL, "charisma" integer DEFAULT NULL, "weapon" integer DEFAULT NULL)    -> 0.1483s #<Dragon:0xb7747f54 @new_record=true, @attributes={"strength"=>0, "type"=>"Dragon", "charisma"=>0, "weapon"=>0, "life"=>0}>   SQL (0.000930) INSERT INTO creatures ("strength", "type", "charisma", "life", "weapon") VALUES(0, 'Dragon', 0, 0, 0) #<Dragon:0xb773e2ec @new_record=true, @attributes={"strength"=>0, "type"=>"Dragon", "charisma"=>0, "weapon"=>0, "life"=>0}>   SQL (0.000742) INSERT INTO creatures ("strength", "type", "charisma", "life", "weapon") VALUES(0, 'Dragon', 0, 0, 0) #<Dragon:0xb773bb8c @new_record=true, @attributes={"strength"=>0, "type"=>"Dragon", "charisma"=>0, "weapon"=>0, "life"=>0}>   SQL (0.000735) INSERT INTO creatures ("strength", "type", "charisma", "life", "weapon") VALUES(0, 'Dragon', 0, 0, 0) #<Dragon:0xb77394b8 @new_record=true, @attributes={"strength"=>0, "type"=>"Dragon", "charisma"=>0, "weapon"=>0, "life"=>0}>   SQL (0.001781) INSERT INTO creatures ("strength", "type", "charisma", "life", "weapon") VALUES(0, 'Dragon', 0, 0, 0) #<Dragon:0xb7734440 @new_record=true, @attributes={"strength"=>0, "type"=>"Dragon", "charisma"=>0, "weapon"=>0, "life"=>0}>   SQL (0.000739) INSERT INTO creatures ("strength", "type", "charisma", "life", "weapon") VALUES(0, 'Dragon', 0, 0, 0) thufir@arrakis ~/Desktop/dwemthys $ thufir@arrakis ~/Desktop/dwemthys $ ruby read_creatures.rb   Creature Load (0.006906) SELECT * FROM creatures   Dragon Update (0.001537) UPDATE creatures SET "charisma" = 0, "strength" = 0, "weapon" = 0, "life" = 0, "type" = 'Dragon' WHERE "id" = 1   Dragon Update (0.000748) UPDATE creatures SET "charisma" = 0, "strength" = 0, "weapon" = 0, "life" = 0, "type" = 'Dragon' WHERE "id" = 2   Dragon Update (0.000731) UPDATE creatures SET "charisma" = 0, "strength" = 0, "weapon" = 0, "life" = 0, "type" = 'Dragon' WHERE "id" = 3 read_creatures.rb:19: undefined local variable or method `green_dragon' for main:Object (NameError)         from read_creatures.rb:17:in `each'         from read_creatures.rb:17 thufir@arrakis ~/Desktop/dwemthys $ thufir@arrakis ~/Desktop/dwemthys $ cat read_creatures.rb require 'fileutils' require 'active_record' require 'creature' require 'dragon' require 'green_dragon'

ActiveRecord::Base.logger = Logger.new(STDERR) ActiveRecord::Base.colorize_logging = true

ActiveRecord::Base.establish_connection(     :adapter => "sqlite3",     :dbfile => "dwemthys.db" )

index = 0 Creature.find(:all).each { |creature|         if (index > 2) then                 creature.type = green_dragon                 creature.weapon = 1000         end         creature.save         index = index+1 }

Creature.find(:all).each { |creature|         puts creature.inspect } thufir@arrakis ~/Desktop/dwemthys $

thanks,

Thufir

2

Ohhh, it's a string. So, the following worked:

thufir@arrakis ~/Desktop/dwemthys $ thufir@arrakis ~/Desktop/dwemthys $ cat read_creatures.rb require 'fileutils' require 'active_record' require 'creature' require 'dragon' require 'green_dragon'

ActiveRecord::Base.logger = Logger.new(STDERR) ActiveRecord::Base.colorize_logging = true

ActiveRecord::Base.establish_connection(     :adapter => "sqlite3",     :dbfile => "dwemthys.db" )

index = 0 Creature.find(:all).each { |creature|         if (index > 2) then                 creature.type = "GreenDragon" #MUST be a string!                 creature.weapon = 1000         end         creature.save         index = index+1 }

Creature.find(:all).each { |creature|         puts creature.inspect } thufir@arrakis ~/Desktop/dwemthys $

thanks,

Thufir