Here is something I found in version 1 of the Agile Web Dev book page 203. If account is an active record and balance is a field, then you can access the field as either account[:balance] = 5 account.balance = 5 The first method is deprecated the book says. However using that method seems like a good way to abstract your fields. You can have: fld = :balance account[fld] = 5 That way suppose you where tyrying to write a sort of framework that operated on various records. None of the records all had the same field names. It seems you might want to access fields in that manner for some such circumstance. Suppose for instance that you had some kind of framework that did special things to the data on various fields based on the nameing convention of each field name. You might want to go iterate through each field in a record and modify it's data based on the name of the field. When you get the record initially, you don't know what all the fields are in the record as you are looking at the record in a more abstract way. It seems like at one point I had tried to do something like that but had some problems, perhaps because either it was not well supported in ActiveRecord or at the time I was not fully aware of what was available, but it was a while ago and I am not sure I remember all the details.
on 2007-01-08 15:26
on 2007-01-08 15:41
surf wrote: > account[:balance] = 5 > account.balance = 5 > > The first method is deprecated the book says. However using that method > seems like a good way to abstract your fields. You can have: > > fld = :balance > account[fld] = 5 This is probably the best way to do that: field = :balance account.send(field) if account.respond_to?(field) The send method calls the "field" method, repsond_to? checks to see if the object can respond to the "field" method. Dan M.
on 2007-01-08 16:22
I forget exactly, but I think I had a module as shown below. I used write_attribute and read_attribute, but I wanted the accessable outside of the record directly which they where not so I used this module and then included that in my record as shown below. I had tried some other ways to access the fields besides the usual way, but they didn't work well. I had started to work on this dateing website idea and it all evolved into this framework and it started to get too pie in the sky. It was really a learning project for Rails. However the problem I have now is trying to explain to potential employers what I did and why I did it that way. I have it all on my lap top but it's not done and I don't have the motivation anymore to mess with it much. I did do some work on another site that's online, but it was a small project. I got laid off from a job where I was doing alot of maintainence programming so I started to work with Rails and needed a complex project to help me learn. I went hog wild with ideas and creativiity for awhile, now I am just trying to find a job. module SqlInterface def write_fld(a,v) write_attribute(a,v) end def read_fld(a) read_attribute(a) end # various other.. end require 'sql_interface' class Profile < ActiveRecord::Base include SqlInterface
on 2007-01-08 17:50
I wonder what happens when you have a field called "class" or any other name that is already a method on a base object. -John
on 2007-01-08 18:02
I think you would access it as a symbol that is: myRec[:class]
on 2007-01-08 18:42
When using inheritance in ActiveRecord to automatically assign a Object's model type, you need a :type field in your table. This lets Rails create inheritance based on that field, and essentially creates a new class. You run into a problem when Rials wants :type to define a class, but class is a Ruby key word. My solution is to create a attr_reader and attr_writer to get and set my Object's type app/models/objects.rb def object_class self[:type] end def object_class=(classin) self[:type] = classin.to_s end Then you can call self.object_class = "MyClass" and "MyClass" is stored in the :type field, and uses a hierchal structure of differnet, but similar Object types in one table.