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Yan Oleg

2008-Nov-21 07:46 UTC

Distinct selection

I have the following code:

members.select {|m| m.role.assignable?}.collect {|m| m.role}.sort

There are two tables: "roles" and "members". One role record
may have
many foreign member records.

But in this case I get many same roles, I want to apply "distinct"
operation to make roles unique in results. How can I do this?
-- 
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Yan Oleg

2008-Nov-21 13:59 UTC

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Re: Distinct selection

Yan Oleg wrote:> I have the following code:
> 
> members.select {|m| m.role.assignable?}.collect {|m| m.role}.sort
> 
> There are two tables: "roles" and "members". One role
record may have
> many foreign member records.
> 
> But in this case I get many same roles, I want to apply
"distinct"
> operation to make roles unique in results. How can I do this?
Please help me!
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James Mitchell

2008-Nov-21 14:13 UTC

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Re: Distinct selection

What exactly are you trying to do?

From reading what you wrote, it sounds like you want a list of roles
that have not already been assigned.  Is that right?

--
James Mitchell



On Fri, Nov 21, 2008 at 8:59 AM, Yan Oleg
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:>
> Yan Oleg wrote:
>> I have the following code:
>>
>> members.select {|m| m.role.assignable?}.collect {|m| m.role}.sort
>>
>> There are two tables: "roles" and "members". One
role record may have
>> many foreign member records.
>>
>> But in this case I get many same roles, I want to apply
"distinct"
>> operation to make roles unique in results. How can I do this?
>
> Please help me!
> --
> Posted via http://www.ruby-forum.com/.
>
> >
>
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Yan Oleg

2008-Nov-21 14:51 UTC

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Re: Distinct selection

James Mitchell wrote:> What exactly are you trying to do?
> 
> From reading what you wrote, it sounds like you want a list of roles
> that have not already been assigned.  Is that right?
> 
> --
> James Mitchell
> 
> 
> 
> On Fri, Nov 21, 2008 at 8:59 AM, Yan Oleg
NO, it isn''t right.

If I use this code:

members.select {|m| m.role.assignable?}.collect {|m| m.role}.sort

...I get several roles with the same ID and NAME, but I want to get 
unique ones, like using DISTINCT operation in SQL statements (SELECT 
DISTINCT name FROM roles.....)

But unfortunately I can get the list from table "members", where
records
may have several same role names:

Manager
Tester
Manager
Manager
Manager
Tester
Developer
Developer
Tester
Developer
Tester
Developer
Developer
Developer

But I have to get this list:

Manager
Tester
Developer
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James Mitchell

2008-Nov-21 18:25 UTC

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Re: Distinct selection

Ok, maybe we misunderstood each other.

If you want a list of roles, why would you go through the members
table to get it?  You can just do Roles.find(:all).map(&:name)

I''m not sure what you doing with "assignable?".  It seems to
be
important to you, but you have not explained what it is supposed to
return.

What does it do?  Does it return:
  a) members who do not have a role and are therefore able to be
assigned a role ?
  b) some awkward pass-through delegation to roles that aren''t assigned
yet ?


--
James Mitchell



On Fri, Nov 21, 2008 at 9:51 AM, Yan Oleg
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:>
> James Mitchell wrote:
>> What exactly are you trying to do?
>>
>> From reading what you wrote, it sounds like you want a list of roles
>> that have not already been assigned.  Is that right?
>>
>> --
>> James Mitchell
>>
>>
>>
>> On Fri, Nov 21, 2008 at 8:59 AM, Yan Oleg
>
> NO, it isn''t right.
>
> If I use this code:
>
> members.select {|m| m.role.assignable?}.collect {|m| m.role}.sort
>
> ...I get several roles with the same ID and NAME, but I want to get
> unique ones, like using DISTINCT operation in SQL statements (SELECT
> DISTINCT name FROM roles.....)
>
> But unfortunately I can get the list from table "members", where
records
> may have several same role names:
>
> Manager
> Tester
> Manager
> Manager
> Manager
> Tester
> Developer
> Developer
> Tester
> Developer
> Tester
> Developer
> Developer
> Developer
>
> But I have to get this list:
>
> Manager
> Tester
> Developer
> --
> Posted via http://www.ruby-forum.com/.
>
> >
>
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Harold

2008-Nov-21 21:53 UTC

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Re: Distinct selection

Agreed with James that we don''t have much info on what you are trying
to achieve. Why can''t you just query the roles table directly?

Anyways, you can always uniq the array:
http://www.ruby-doc.org/core/classes/Array.html#M002237




On Nov 21, 1:25 pm, "James Mitchell"
<jmitc...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> Ok, maybe we misunderstood each other.
>
> If you want a list of roles, why would you go through the members
> table to get it?  You can just do Roles.find(:all).map(&:name)
>
> I''m not sure what you doing with "assignable?".  It
seems to be
> important to you, but you have not explained what it is supposed to
> return.
>
> What does it do?  Does it return:
>   a) members who do not have a role and are therefore able to be
> assigned a role ?
>   b) some awkward pass-through delegation to roles that aren''t
assigned yet ?
>
> --
> James Mitchell
>
> On Fri, Nov 21, 2008 at 9:51 AM, Yan Oleg
>
> <rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote:
>
> > James Mitchell wrote:
> >> What exactly are you trying to do?
>
> >> From reading what you wrote, it sounds like you want a list of
roles
> >> that have not already been assigned.  Is that right?
>
> >> --
> >> James Mitchell
>
> >> On Fri, Nov 21, 2008 at 8:59 AM, Yan Oleg
>
> > NO, it isn''t right.
>
> > If I use this code:
>
> > members.select {|m| m.role.assignable?}.collect {|m| m.role}.sort
>
> > ...I get several roles with the same ID and NAME, but I want to get
> > unique ones, like using DISTINCT operation in SQL statements (SELECT
> > DISTINCT name FROM roles.....)
>
> > But unfortunately I can get the list from table "members",
where records
> > may have several same role names:
>
> > Manager
> > Tester
> > Manager
> > Manager
> > Manager
> > Tester
> > Developer
> > Developer
> > Tester
> > Developer
> > Tester
> > Developer
> > Developer
> > Developer
>
> > But I have to get this list:
>
> > Manager
> > Tester
> > Developer
> > --
> > Posted viahttp://www.ruby-forum.com/.--~--~---------~--~----~------------~-------~--~----~
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Yan Oleg

2008-Nov-25 10:39 UTC

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Re: Distinct selection

"assignable?" is just a filter to select roles that have attribute 
"assignable" set to true.

Regarding roles... I want to select not all roles, but roles that are 
members of project. And also I cannot change database structure. So I 
have the following entities relations:

Roles <- Members -> Projects
          |
         \ /
         Users


Unfortunately I don''t know how to select (using RoR) unique roles that 
regard only defined project.

In SQL it looks like:

SELECT Roles.id, Roles.name
FROM Roles, Members
WHERE Members.project_id=5
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Yan Oleg

2008-Nov-25 13:14 UTC

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Re: Distinct selection

Thanks to Harold. I used uniq method and it worksfine!! :)
Thank you!
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Rails - Nov 2008 - Distinct selection

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