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In some part of my code I ended writing the following: [ruby] self.count_processed ||= 0 self.count_processed += 1 [/ruby] where self is some ActiveRecord model, and count_processed is an attribute of that model (and stored in the database). What am i trying to achieve (if it is not blatantly obvious):

  • if count_processed is not initialised, make it zero
  • increment count_processed Imho this code is clear and readable, but I had the feeling it could be more concise/prettier. So I asked that question on our campfire, to see if we could come up with something shorter. Very nice to be working in a team where you can just throw up questions like these and a very useful, educational discussion unfolds. In short we came up with the following solutions.

Solution 1: to_i

[ruby] self.count_processed = self.count_processed.to_i + 1 [/ruby] Nifty! Isn't it? Use to_i because it will handle the nil correctly. But for me this looked wrong. If I would return to this code after a few weeks, months, I would wonder why I did this way, and not just wrote self.count_processed += 1. So while the code is correct, the intent of the code is not clear.

Solution 2: concise!

[ruby] self.count_processed = (self.count_processed || 0) + 1 [/ruby] This is very beautiful, and the intent is also very clear. If it is not initialised, use the zero, else just use the value and add 1. Awesome.

Solution 3: change the getter

And alternative solution would be to overwrite the getter, like this [ruby] def count_processed self[:count_processed] ||= 0 end [/ruby] Note the notation we used: we use self[:count_processed] because this will fetch the value from the database column. If this was a normal getter, we would write @count_processed (but that does not work for an ActiveRecord model). After redefining the getter, we can just write: [ruby] self.count_processed += 1 [/ruby] While this will work always, does it express its intent more clearly or not? Actually you no longer have to worry about the initialisation, because it is handled, and we can focus on what we really want: increment the counter. I opted for this solution.

What about you?

Which version do you prefer? Do you have any alternative suggestions?

rspec testing using macros

[ruby wraplines="false"] STATUS_EXPECTED_TRANSLATIONS = [[inp1, outp1], ... ] it "should translate received statuses" do STATUS_EXPECTED_TRANSLATIONS.each do |tr| controller.send('translate_status_to_envelope_status', tr[0]).should == tr[1] end end [/ruby] While this is short and DRY, a problem arises when one of the values in my look-up table does not behave as expected anymore. The complete test will fail, without having any clue which value caused it to fail. That is not good! But luckily, in rspec there exists the option to use macros. It is a kind of templates for tests. Using macros i could write this much cleaner, and generate my test-clauses on the fly. [ruby wraplines="false"] STATUS_EXPECTED_TRANSLATIONS.each do |tr| it "should translate #tr[0]} to success" do controller.send('translate_status_to_envelope_status', tr[0]).should == tr[1] end end [/ruby] Now if a test fails, i know which i value need to check, because i will get an appropriate error-message.

refactoring ruby code

Most of my ruby/rails development is against a legacy Oracle database. One of the things we needed to fix, was a user-table with not enough fields. Because the user table was shared with another application, we were not able to alter the table. So we added another table, user_params, containing possibly extra parameters for each user. Now it would be nice if each of those possible parameters would behave like a real attribute. So, first implementation: [ruby] class User < ActiveRecord::Base set_primary_key "user_name" set_table_name "stca_user" set_sequence_name "autogenerated" # do not use a sequence at insert! validates_presence_of :user_name validates_presence_of :password # define some virtual attributes for attributes defined in the UserParam table def group_name UserParam.get_param_value(self.user_name, 'UserGroup') end def group_name=(value) UserParam.set_param_value(self.user_name, 'UserGroup', value) end def title UserParam.get_param_value(self.user_name, 'UserTitle') end def title=(value) UserParam.set_param_value(self.user_name, 'UserTitle', value) end def language UserParam.get_param_value(self.user_name, 'UserLanguage') end def language=(value) UserParam.set_param_value(self.user_name, 'UserLanguage', value) end def full_name UserParam.get_param_value(self.user_name, 'UserFullName') end def full_name=(value) UserParam.set_param_value(self.user_name, 'UserFullName', value) end def email UserParam.get_param_value(self.user_name, 'UserEmail') end def email=(value) UserParam.set_param_value(self.user_name, 'UserEmail', value) end # ... snipped away more code end [/ruby] Obviously, this code is not DRY. At lot of repetition, like the stuff i hate about C# or java properties. This could be done better, let's just generate the methods: [ruby] class User < ActiveRecord::Base set_primary_key "user_name" set_table_name "stca_user" set_sequence_name "autogenerated" # do not use a sequence at insert! validates_presence_of :user_name validates_presence_of :password # define some virtual attributes for attributes defined in the UserParam table instance_eval do [['group_name', 'UserGroup'], ['title', 'UserTitle'], ['language','UserLanguage'], ['full_name', 'UserFullName'], ['email', 'UserEmail']].each do |arr| define_method arr[0].to_sym do UserParam.send('get_param_value', self.user_name, arr[1]) end define_method "#{arr[0]}=" do |value| UserParam.send("set_param_value", self.user_name, arr[1], value) end end end end [/ruby] This looks nice. One disadvantage might be that this is not very readable. At first glance it is no longer clear which attributes are available. But with models that is always the case. A few things can still be improved. Every get and set is a query against the database. We might want to improve upon that, and cache results. Also saving the virtual fields is now done when they are being set, but at that time the parent "User" might still not be saved. So this still calls for a better solution. But this does show why i like ruby so much. It makes me feel powerful :)