Dave Sims
2010-Jan-28 17:52 UTC
What is the purpose of :conditions on a belongs_to association?
Say I have the following association with an attached condition:
belongs_to :admin_user,
:class_name => ''User'',
:foreign_key => :admin_user_id,
:conditions=> ''users.admin=TRUE'' # or any variation
with hash or
array, {:admin => true}, etc.
The API
states<http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#M001835>that
the :conditions option on belongs_to will:
Specify the conditions that the associated object must meet in order to
be> included as a WHERE SQL fragment, such as authorized = 1.
>
But the output shows no WHERE clause on the select, and in any case I would
expect that conditions like this on a belongs_to would prevent persisting
that relationship to begin with, on the INSERT not the SELECT. This option
seems to have no effect on a belongs_to association, unless I''m missing
something. The option makes sense on a has_many, I just don''t see how
it
applies to belongs_to.
I''ve posted this on
stackoverflow<http://stackoverflow.com/questions/2156514/what-is-the-purpose-of-conditions-on-a-belongs-to-association>as
well, just fyi.
Thanks,
Dave
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Robert Walker
2010-Jan-28 20:00 UTC
Re: What is the purpose of :conditions on a belongs_to asso
Dave Sims wrote:> But the output shows no WHERE clause on the select, and in any case I > would > expect that conditions like this on a belongs_to would prevent > persisting > that relationship to begin with, on the INSERT not the SELECT. This > option > seems to have no effect on a belongs_to association, unless I''m missing > something. The option makes sense on a has_many, I just don''t see how it > applies to belongs_to.Take this contrived example: Department has_many :people end Person belongs_to :department, :conditions => { :name => "Development" } end person # assume this exists person.department.name => "Development" department # assume this exists department.name => "Marketing" person.department = department person.save person.reload person.department => nil SELECT * FROM "departments" WHERE ("departments"."id" = 1 AND ("departments"."name" = ''Development'')) -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Dave Sims
2010-Jan-28 21:40 UTC
Re: Re: What is the purpose of :conditions on a belongs_to asso
Upon further inspection I do see that the condition will restrict the * retrieval* of items (and even then only after they are reloaded), but not the persistence. I can assign an invalid object (invalid according to the condition) and that reference is persisted to the database upon save. The invalid attribute will be available on that object in memory until the object is reloaded. On Thu, Jan 28, 2010 at 2:00 PM, Robert Walker <lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org> wrote:> Dave Sims wrote: > > But the output shows no WHERE clause on the select, and in any case I > > would > > expect that conditions like this on a belongs_to would prevent > > persisting > > that relationship to begin with, on the INSERT not the SELECT. This > > option > > seems to have no effect on a belongs_to association, unless I''m missing > > something. The option makes sense on a has_many, I just don''t see how it > > applies to belongs_to. > > Take this contrived example: > > Department > has_many :people > end > > Person > belongs_to :department, :conditions => { :name => "Development" } > end > > person # assume this exists > person.department.name > => "Development" > department # assume this exists > department.name > => "Marketing" > person.department = department > person.save > person.reload > person.department > => nil > > SELECT * FROM "departments" WHERE ("departments"."id" = 1 AND > ("departments"."name" = ''Development'')) > -- > Posted via http://www.ruby-forum.com/. > > -- > You received this message because you are subscribed to the Google Groups > "Ruby on Rails: Talk" group. > To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org > To unsubscribe from this group, send email to > rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org<rubyonrails-talk%2Bunsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org> > . > For more options, visit this group at > http://groups.google.com/group/rubyonrails-talk?hl=en. > >-- And all the Knave e’er wanted was his rug As spoken of, which tied the room together. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Chris Drappier
2010-Jan-28 21:47 UTC
Re: Re: What is the purpose of :conditions on a belongs_to asso
read the documentation on this. it explains it pretty thoroughly. On Thu, Jan 28, 2010 at 3:40 PM, Dave Sims <davsims-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> Upon further inspection I do see that the condition will restrict the * > retrieval* of items (and even then only after they are reloaded), but not > the persistence. I can assign an invalid object (invalid according to the > condition) and that reference is persisted to the database upon save. The > invalid attribute will be available on that object in memory until the > object is reloaded. > > On Thu, Jan 28, 2010 at 2:00 PM, Robert Walker <lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>wrote: > >> Dave Sims wrote: >> > But the output shows no WHERE clause on the select, and in any case I >> > would >> > expect that conditions like this on a belongs_to would prevent >> > persisting >> > that relationship to begin with, on the INSERT not the SELECT. This >> > option >> > seems to have no effect on a belongs_to association, unless I''m missing >> > something. The option makes sense on a has_many, I just don''t see how it >> > applies to belongs_to. >> >> Take this contrived example: >> >> Department >> has_many :people >> end >> >> Person >> belongs_to :department, :conditions => { :name => "Development" } >> end >> >> person # assume this exists >> person.department.name >> => "Development" >> department # assume this exists >> department.name >> => "Marketing" >> person.department = department >> person.save >> person.reload >> person.department >> => nil >> >> SELECT * FROM "departments" WHERE ("departments"."id" = 1 AND >> ("departments"."name" = ''Development'')) >> -- >> Posted via http://www.ruby-forum.com/. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Ruby on Rails: Talk" group. >> To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org >> To unsubscribe from this group, send email to >> rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org<rubyonrails-talk%2Bunsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org> >> . >> For more options, visit this group at >> http://groups.google.com/group/rubyonrails-talk?hl=en. >> >> > > > -- > And all the Knave e’er wanted was his rug > As spoken of, which tied the room together. > > > -- > You received this message because you are subscribed to the Google Groups > "Ruby on Rails: Talk" group. > To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org > To unsubscribe from this group, send email to > rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org<rubyonrails-talk%2Bunsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org> > . > For more options, visit this group at > http://groups.google.com/group/rubyonrails-talk?hl=en. >-- Chris Drappier Software Developer Analytical Mechanics Associates, INC. Office : 256-830-4811 x114 Cell : 256-665-2832 -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Dave Sims
2010-Jan-29 01:32 UTC
Re: Re: What is the purpose of :conditions on a belongs_to asso
If you know of documentation in addition to the api docs linked from my original post which might be helpful, feel free to include a link. On Thu, Jan 28, 2010 at 3:47 PM, Chris Drappier <chris.drappier-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>wrote:> read the documentation on this. it explains it pretty thoroughly. > > On Thu, Jan 28, 2010 at 3:40 PM, Dave Sims <davsims-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote: > >> Upon further inspection I do see that the condition will restrict the * >> retrieval* of items (and even then only after they are reloaded), but not >> the persistence. I can assign an invalid object (invalid according to the >> condition) and that reference is persisted to the database upon save. The >> invalid attribute will be available on that object in memory until the >> object is reloaded. >> >> On Thu, Jan 28, 2010 at 2:00 PM, Robert Walker <lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>wrote: >> >>> Dave Sims wrote: >>> > But the output shows no WHERE clause on the select, and in any case I >>> > would >>> > expect that conditions like this on a belongs_to would prevent >>> > persisting >>> > that relationship to begin with, on the INSERT not the SELECT. This >>> > option >>> > seems to have no effect on a belongs_to association, unless I''m missing >>> > something. The option makes sense on a has_many, I just don''t see how >>> it >>> > applies to belongs_to. >>> >>> Take this contrived example: >>> >>> Department >>> has_many :people >>> end >>> >>> Person >>> belongs_to :department, :conditions => { :name => "Development" } >>> end >>> >>> person # assume this exists >>> person.department.name >>> => "Development" >>> department # assume this exists >>> department.name >>> => "Marketing" >>> person.department = department >>> person.save >>> person.reload >>> person.department >>> => nil >>> >>> SELECT * FROM "departments" WHERE ("departments"."id" = 1 AND >>> ("departments"."name" = ''Development'')) >>> -- >>> Posted via http://www.ruby-forum.com/. >>> >>> -- >>> You received this message because you are subscribed to the Google Groups >>> "Ruby on Rails: Talk" group. >>> To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org >>> To unsubscribe from this group, send email to >>> rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org<rubyonrails-talk%2Bunsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org> >>> . >>> For more options, visit this group at >>> http://groups.google.com/group/rubyonrails-talk?hl=en. >>> >>> >> >> >> -- >> And all the Knave e’er wanted was his rug >> As spoken of, which tied the room together. >> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Ruby on Rails: Talk" group. >> To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org >> To unsubscribe from this group, send email to >> rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org<rubyonrails-talk%2Bunsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org> >> . >> For more options, visit this group at >> http://groups.google.com/group/rubyonrails-talk?hl=en. >> > > > > -- > Chris Drappier > Software Developer > Analytical Mechanics Associates, INC. > Office : 256-830-4811 x114 > Cell : 256-665-2832 > > -- > You received this message because you are subscribed to the Google Groups > "Ruby on Rails: Talk" group. > To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org > To unsubscribe from this group, send email to > rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org<rubyonrails-talk%2Bunsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org> > . > For more options, visit this group at > http://groups.google.com/group/rubyonrails-talk?hl=en. >-- And all the Knave e’er wanted was his rug As spoken of, which tied the room together. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Robert Walker
2010-Jan-29 14:36 UTC
Re: Re: What is the purpose of :conditions on a belongs_to
Dave Sims wrote:> If you know of documentation in addition to the api docs linked from my > original post which might be helpful, feel free to include a link.As mentioned, the API doc actually does explain this relatively clearly in this statement: :conditions Specify the conditions that the associated object must meet in order to be included as a WHERE SQL fragment, such as authorized = 1. The :conditions option applies to the associated object as a WHERE SQL fragment. There is no mention of any validation, or referential integrity. Rather it is a "filter" on the association. It simply determines whether or not the referenced object is returned. If you need validation of the association, then use validation. ActiveRecord provides reasonably extensive validation support. That, along with database referential integrity, is the right place for ensuring validity. -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.