activerecord.rb

require 'active_record'

ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Base.establish_connection(
    :adapter  => "postgresql",
    :host     => 'localhost',
    :username => 'murat',
    :password => '',
    :database => 'lighthouse_2015_05',
    :encoding => 'utf8',
)

class Contact < ActiveRecord::Base

    validates :email, format: { with: /[\w]+@[\w]+\.[\w]+/, message: "Please enter a valid email" }

end

contacts = Contact.all
# puts contacts

murat = Contact.new(name: "Murat", email: "[email protected]", phone: "778 858 8449")
# murat.save

murat.email = "INVALID"
if murat.save
    puts "success"
else
    puts murat.errors.full_messages.inspect
end



# someone = Contact.find(2)
# someone.destroy

#children = Contact.where("age < ?", 12)
#children.each do |child|
#    puts child.name, child.age
# end

orm.rb

require 'pg'

CONN = PG::Connection.new({
    host: 'localhost',
    user: 'murat',
    password: '',
    dbname: 'lighthouse_2015_05'
})



class Orm

    def initialize(attributes)

        attributes.each do |key, value|
            instance_key = "@#{key}"

            # set the value of the instance var
            instance_variable_set(instance_key, value)

            # generate getter & setter
            self.class.__send__(:attr_accessor, key)
        end
    end

    def get_attributes
        vars = []
        instance_variables.each do |item|
            if item != :@id
                vars << item[1..-1]
            end
        end
        vars
    end

    def get_key_value_strings
        get_attributes.map do |key|
            value = instance_variable_get("@#{key}")
            "#{key} = '#{value}'"
        end
    end

    def self.table_name
        "#{self.to_s.downcase}s"
    end

    def save
        if @id
            key_value_list = get_key_value_strings.join(", ")
            @id = @id.to_i
            sql = "UPDATE #{self.class.table_name} SET #{key_value_list} WHERE id=#{@id}"
            puts sql
            CONN.exec(sql)

        else
            puts "creating"
        end

    end

    def self.find(id)
        results = CONN.exec_params("SELECT * FROM #{self.table_name} WHERE id=$1", [id])
        if results.ntuples > 0
            attributes = results[0]
        else
            return nil
        end

        self.new(attributes)
    end

    def destroy
    end

    def test
        @table
    end
end

class Contact < Orm
end

class Message < Orm
end

contact = Contact.find(1)

# SQL Injection!!! careful.
contact.name = "Tarum'; DROP TABLE contacts; -- "
contact.save