How can I save a unique string by incrementing it in rails? - mysql

Question

How can I save a unique string to my database and if the value exists increment it.
The behaviour I'm after is similar to when you save a file e.g. foo.txt, foo1.txt
I do NOT want to return a 'not unique value' error message.
class Person < ActiveRecord::Base
attr_accessible :name
end
Person.create(:name => 'Dave') # => 'Dave'
Person.create(:name => 'Dave') # => 'Dave1'
Person.create(:name => 'Dave') # => 'Dave2'
I'm using ruby, rails and mysql

Answer 1

you don't need to set validation uniqueness to your model . You can use something like this:
class Person < ActiveRecord::Base
attr_accessible :name
before_create :check_and_increment
private
def check_and_increment
if Person.exists? name: self.name
similar_persons = get_all_with_same_name self.name
next_num = similar_persons.max_by{|m| m.scan(/\d+/)}.scan(/\d+/).first.nil? ? 1 : similar_persons.max_by{|m| m.scan(/\d+/)}.scan(/\d+/).first.to_i + 1
self.name = "#{self.name}#{next_num}"
else
true
end
end
def get_all_with_same_name name
where("name LIKE ?", 'name%')
end
end
This is simple idea for your problem. Need to be carefull with persons like Anna and Annastasia, for example . These persons has different names but their names are overlap.
Hope this will help you .

Answer 2

I could not find any rails or mysql features to do this so I created the follow 3 methods and
def unique_name(name)
if Person.exists?(:name => name)
generate_unique_name(name)
else
name
end
end
def similar_names(name)
Person.where("name LIKE ?", "#{name}%").pluck(:name)
end
def generate_unique_name(name)
number = similar_names(name).map{ |a| a.scan(/\d+$/).max.to_i }.compact.max.to_i + 1
"#{name} #{number}"
end
...
Person.create(:name => unique_name('Dave'))