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[ardder]

No description provided.

[jwo]

Sorry about missing this! I'm on it this morning.

[jwo]

Later we use this method (add) as:

puts "[#{movie.title}] is already on your list!" unless movie_list.add(movie)

This means this method is responsible for two things:

1. keeping the movies unique (prevent dupes)
2. telling you if the movie was a dupe

There are exceptions to this rule, but I think Command/Query separation is a good one to follow. More: http://martinfowler.com/bliki/CommandQuerySeparation.html & http://tony.pitluga.com/2011/08/04/command-query-separation-in-ruby.html

In this specific case, I might add a "contains?" method

if movie_list.contains? movie
  puts "[#{movie.title}] is already on your list!"
else
  movie_list.add movie
end

thoughts? what do you think?

[ardder]

Thanks for the links about Command/Query separation!

The idea of MovieList#add is actually derived from ActiveRecord::Base#save. I want to use the return value (true/false) to let the user know if he adds the movie successfully or not.

After reading the links, I think that separating the two idea is a better and cleaner design. But inside the MovieList#add, I still want to check if the argument is duplicated or not. Because I believe that MovieList#add should have the responsibility to protect the internal data from messed up by the user.

When I try to implement the new method, how to handle bad argument comes into question. Should I just neglect it or throw an exception? Which one will you choose? Or, maybe you have a better idea? 😄

[jwo]

sure, I can buy that -- if you want MovieList#add to not:

1. not add the item if it exists
2. tell the program something bad happened if someone tried to add a dupe:

in MovieList#add I would raise an exception if it is contained when you try to add it.

[jwo]

Most excellent job! especially with the tests! Go you!