CODEWITHSUNDEEP
design-patternsdao
Quarktum
Quarktum

Reputation: 709

What returns a DAO?

Lets suppose that I have two classes Foo and Bar with each respective DAO.

Lets say that a foo has many bars.

So the method that returns the bars of a foo where should it go?

class FooDAO
  def bars_from_foo(foo)
    # return the bars of that foo
  end
end

class BarDAO
  def bars_from_foo(foo)
    # returns the bars of that foo
  end
end

My doubt is, does FooDAO only return foo objects? Or does FooDAO only include the methods that a foo will need?

In my opinion, I choose the first one: FooDAO only returns foo objects. Because, the method could be used from another class, that has nothing in common with the other DAO. I can't think in an example right now.

I would like to read some opinions from experts.

Upvotes: 0

Views: 36

Answers (1)

ruakh
ruakh

Reputation: 183514

There are two approaches:

  • The fact that a foo has many bars can actually be modeled in your Foo class: foo.get_bars() would return the bars. FooDAO would then be responsible for making sure that this works properly, either by fetching the bars at instantiation time or by using lazy-loading.
  • The fact that a bar has a corresponding foo can be viewed as a search criterion for bar. BarDAO would then have a find_bars_by_foo_id(foo_id) or find_bars_by_foo(foo). (This is pretty similar to your second possibility; the key is to think about it the right way.) Alternatively, it would have a find_bars(criteria), where criteria can have settings such as the foo_id to use.

Which approach is most appropriate will depend on the semantics of the two classes and of the relationship between them.

Upvotes: 1

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