I''m trying to find an elegant solution to a data model problem and was wondering if some of you good people could help. I''m setting up a simple book-loan tracking system, where an office has many people and people have many books. i.e.: office --> (has many) people --> (has many) books while office.people returns a list of people belonging to an office and people.books returns a list of books belonging to a person, is there a function such as office.books that would return all of the books belonging to all of the people in the office? Thanks, -Neal -- Posted via http://www.ruby-forum.com/.
I don''t think thats build in, but you could very easily define a method in office (books). Neal wrote:>I''m trying to find an elegant solution to a data model problem and was >wondering if some of you good people could help. I''m setting up a >simple book-loan tracking system, where an office has many people and >people have many books. i.e.: > >office --> (has many) people --> (has many) books > >while office.people returns a list of people belonging to an office and >people.books returns a list of books belonging to a person, is there a >function such as office.books that would return all of the books >belonging to all of the people in the office? > >Thanks, >-Neal > > >
Neal wrote:> I''m trying to find an elegant solution to a data model problem and was > wondering if some of you good people could help. I''m setting up a > simple book-loan tracking system, where an office has many people and > people have many books. i.e.: > > office --> (has many) people --> (has many) books > > while office.people returns a list of people belonging to an office and > people.books returns a list of books belonging to a person, is there a > function such as office.books that would return all of the books > belonging to all of the people in the office? > > Thanks, > -NealThis may not be the most eligant solution but I would add a method to your ''book'' model similar to this: def self.find_all_by_office_id(office_id) book_collections = Person.find_all_by_office_id(office_id).collect { |p| p.books } book_collections.flatten! end In a controller I would then use: books_by_office = Book.find_all_by_office_id(office.id) Hope this helps a bit. -- Posted via http://www.ruby-forum.com/.
Juraci Krohling Costa wrote:> def books > Book.find(:all, :conditions=>["person_id IN (?)", > people.collect{|person| person.id}.join(", ")] ) ## not tested > endThat function works great! Thanks! How exactly is it joining the tables, though??? Thanks -- Posted via http://www.ruby-forum.com/.
def books
Book.find(:all, :conditions=>["person_id IN (?)",
people.collect{|person| person.id}.join(", ")] ) ## not tested
end
Neal wrote:
>I''m trying to find an elegant solution to a data model problem and
was
>wondering if some of you good people could help. I''m setting up a
>simple book-loan tracking system, where an office has many people and
>people have many books. i.e.:
>
>office --> (has many) people --> (has many) books
>
>while office.people returns a list of people belonging to an office and
>people.books returns a list of books belonging to a person, is there a
>function such as office.books that would return all of the books
>belonging to all of the people in the office?
>
>Thanks,
>-Neal
>
>
>
Neal <nlober-LjrMLQOZ86MlJZD/S0VCNg@public.gmane.org> wrote:> Juraci Krohling Costa wrote: >> def books >> Book.find(:all, :conditions=>["person_id IN (?)", >> people.collect{|person| person.id}.join(", ")] ) ## not tested >> end > > That function works great! Thanks! > > How exactly is it joining the tables, though???The "join" message is not an SQL join operation. It is a collection method that joins all the items in a collection into a string, separated by in this case a comma. What that code does is fetches all the books that belong to any person in that office by filtering on the person_id value of the book, where the people collection equals office.people. There is of course a way to do that all in SQL - you''ll have to decide which approach is better for your uses. -- Posted via http://www.ruby-forum.com/.
Er.. its not joining... You cannot use :include in two level''s in
ActiveRecord, but, I think the last thing you want to do w/ this method
is something like this: office.books.people.books :-)
If you really need to join books w/ people in this method, uses this:
def books
Book.find(:all, :include=>:person, :conditions=>["person_id IN
(?)", people.collect{|person| person.id}.join(", ")] ) ## you
told me this works =D
end
Neal <nlober-LjrMLQOZ86MlJZD/S0VCNg@public.gmane.org> wrote:
>Juraci Krohling Costa wrote:
>
>
>>def books
>> Book.find(:all, :conditions=>["person_id IN (?)",
>>people.collect{|person| person.id}.join(", ")] ) ## not tested
>>end
>>
>>
>
>That function works great! Thanks!
>
>How exactly is it joining the tables, though???
>
>Thanks
>
>
>
On 12/12/05, Juraci Krohling Costa <juca-+BZ7G6WzYWuZuzBka8ofvg@public.gmane.org> wrote:> def books > Book.find(:all, :conditions=>["person_id IN (?)", > people.collect{|person| person.id}.join(", ")] ) ## not tested > end >I''m trying to use this method but I have a problem. This inserts everything like a string example .... IN (''1,3'') Is there any way to avoid rails to add those quotes? Thanks, Santiago
On 12/13/05, Santiago Erquicia <santiago.erquicia-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> On 12/12/05, Juraci Krohling Costa <juca-+BZ7G6WzYWuZuzBka8ofvg@public.gmane.org> wrote: > > def books > > Book.find(:all, :conditions=>["person_id IN (?)", > > people.collect{|person| person.id}.join(", ")] ) ## not tested > > end > > > > > I''m trying to use this method but I have a problem. This inserts > everything like a string example .... IN (''1,3'') > > Is there any way to avoid rails to add those quotes? > > Thanks, > Santiago >OK, I solved this by myself. Book.find(:all, :conditions=>"person_id IN #{people.collect{|person| person.id}.join('', '')}") Santiago