Jim Burgess
2011-Jan-14 15:39 UTC
Why won''t write_attribute(:price, value*100) work in the console?
Hi, I''m confused as to why this code example (from a book) won''t work. They want to store a price in cents, but be able to set it and query it in Euros. To this end they are overwriting the getter and setter methods. In my model: class Product < ActiveRecord::Base def price Product.read_attribute(:price)/100.0 end def price=(value) Product.write_attribute(:price, value*100) end end In the console: r = Product.new => #<Product id: nil, name: nil, price: nil, enabled: true, created_at: nil, updated_at: nil> r.price = 10 NoMethodError: undefined method `write_attribute'' for #<Class:0x6182658> There is no mention of a typo in the book''s errata, write_attribute doesn''t appear to have been removed from rails, so I''m guessing something changed with rails which makes this not work. I did some googling and saw that shorthand for read/write_attribute() is self[] I tried the following and it worked great: class Product < ActiveRecord::Base def price self[:price]/100.0 end def price=(value) self[:price] = value*100 end end r = Product.new => #<Product id: nil, name: nil, price: nil, enabled: true, created_at: nil, updated_at: nil> r.price = 10 => 10 Could anyone tell me why the first example produces a NoMethodError and the second one works just fine? Thanks very much. -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Frederick Cheung
2011-Jan-14 15:43 UTC
Re: Why won''t write_attribute(:price, value*100) work in the console?
On Jan 14, 3:39 pm, Jim Burgess <li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org> wrote:> Could anyone tell me why the first example produces a NoMethodError and > the second one works just fine? >because read/write_attribute are instance methods, but you''re trying to call them on Product (ie a class). self.read_attribute (or just read_attribute) should work fine Fred> Thanks very much. > > -- > Posted viahttp://www.ruby-forum.com/.-- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Jim Burgess
2011-Jan-14 16:16 UTC
Re: Why won''t write_attribute(:price, value*100) work in the console?
Cheers Fred, That was actually embarrassingly obvious. Thanks for your help. -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.