Rails - Mar 2006 - deleting from hash question

I''m a ruby newbie and have what is probably a relatively simple problem
I''m trying to solve. Say that I created a hash:

TASKS = {
    "homework" => "Do Your Homework",
    "chores" => "Your Have Chores",
    "exercise" => "Don''t Forget to Exercise"
  }

and then I had an Assignment model with:

def self.find_assignments(person)
    find(:all, :conditions => ["person_id = ?", person .id])
end

Which I called in the controller like so:

@current_assignments = Assignment.find_assignments(@person)

So, @current_assignments works fine. Now, the problem. I want to display 
the tasks which have NOT yet been assigned (so that they can be assigned 
if desired). In the assignments table, I have a column called
''tasks''
which correlates with the keys in the TASKS hash. So I just want to 
remove any key=>value pairs from TASKS that match with the
''tasks''
column in @current_assignment and then loop through the resulting new 
hash in the view.

I''m at a loss as how best to do this. It must be something so simple 
it''s eluding me. Any suggestions?

-- 
Posted via http://www.ruby-forum.com/.

Sorry, perhaps I just didn''t provide enough specific info. Trying
again:

Since this is a multi-user system, there is no way to query the database 
for unassigned tasks. I''m only inserting lines in the assignments table
when they currently exist for a particular person. If a "task" is not 
assigned, then there is no entry for that task and person combo. So, all 
I really have to go by is the static hash list of TASKS, which is a 
complete list of all available tasks in the system which could 
potentially be assigned to a person. And I need to compare the hash from 
the database of "currently assigned" tasks to my static one of
"all
available" so that I can remove them and be left with a list of 
"currently unassigned tasks".

I want to have a method in the assignments model with 
self.find_unassigned(person), but since I can''t query the result, I
need
to figure out how to compare my hash against the already existing 
self.find_assignments() method. It''s the comparing of the two (very 
different) hashes that is perplexing me. I have this:


TASKS = {
    "homework" => "Do Your Homework",
    "chores" => "Your Have Chores",
    "exercise" => "Don''t Forget to Exercise"
  }.freeze


and I have something like this that rail''s "find" gives me on
the
assignments table:

db_result = {
  "123" => {"id" => "123",
"person_id" => "11", "task" =>
"homework"},
  "456" => {"id" => "456",
"person_id" => "11", "task" =>
"chores"},
  "789" => {"id" => "789",
"person_id" => "11", "task" =>
"exercise"},
}

So, using some elegant ruby code that I can''t seem to find, I need to 
dig down into the db result hash, looping through and comparing it to my 
static hash, and then remove the key=>value pairs from my static hash in 
the instances where has_value? matches.

Suggestions?

-- 
Posted via http://www.ruby-forum.com/.

On Mar 17, 2006, at 3:11 AM, Ryan Williams wrote:
> TASKS = {
>     "homework" => "Do Your Homework",
>     "chores" => "Your Have Chores",
>     "exercise" => "Don''t Forget to
Exercise"
>   }

Here this should be what you want:

ezra-zygmuntowiczs-computer:~/sub ez$ irb
irb(main):001:0> TASKS = {
irb(main):002:1*     "homework" => "Do Your Homework",
irb(main):003:1*     "chores" => "Your Have Chores",
irb(main):004:1*     "exercise" => "Don''t Forget to
Exercise"
irb(main):005:1>   }
=> {"chores"=>"Your Have Chores",
"homework"=>"Do Your Homework",
"exercise"=>"Don''t Forget to Exercise"}
irb(main):006:0> TASKS.delete "chores"
=> "Your Have Chores"
irb(main):007:0> TASKS
=> {"homework"=>"Do Your Homework",
"exercise"=>"Don''t Forget to
Exercise"}


Cheers-
-Ezra
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On 3/17/06, Ryan Williams <ryan@jimmyether.com>
wrote:
> Sorry, perhaps I just didn''t provide enough specific info. Trying
again:
>
> Since this is a multi-user system, there is no way to query the database
> for unassigned tasks. I''m only inserting lines in the assignments
table
> when they currently exist for a particular person. If a "task" is
not
> assigned, then there is no entry for that task and person combo. So, all
> I really have to go by is the static hash list of TASKS, which is a
> complete list of all available tasks in the system which could
> potentially be assigned to a person. And I need to compare the hash from
> the database of "currently assigned" tasks to my static one of
"all
> available" so that I can remove them and be left with a list of
> "currently unassigned tasks".
>
> I want to have a method in the assignments model with
> self.find_unassigned(person), but since I can''t query the result,
I need
> to figure out how to compare my hash against the already existing
> self.find_assignments() method. It''s the comparing of the two
(very
> different) hashes that is perplexing me. I have this:
>
>
> TASKS = {
>     "homework" => "Do Your Homework",
>     "chores" => "Your Have Chores",
>     "exercise" => "Don''t Forget to
Exercise"
>   }.freeze
>
>
> and I have something like this that rail''s "find" gives
me on the
> assignments table:
>
> db_result = {
>   "123" => {"id" => "123",
"person_id" => "11", "task" =>
"homework"},
>   "456" => {"id" => "456",
"person_id" => "11", "task" =>
"chores"},
>   "789" => {"id" => "789",
"person_id" => "11", "task" =>
"exercise"},
> }
>
> So, using some elegant ruby code that I can''t seem to find, I need
to
> dig down into the db result hash, looping through and comparing it to my
> static hash, and then remove the key=>value pairs from my static hash in
> the instances where has_value? matches.
>
> Suggestions?
Haven''t tested, but maybe something like this?

db_result.each {|row| TASKS.delete(row[''task''])}

Justin

> Haven''t tested, but maybe something like this?
> 
> db_result.each {|row| TASKS.delete(row[''task''])}
That didn''t quite work, but thanks! The answer ended up being to creat 
the following method in my Attachment model:

  def self.get_unassigned(assigned)
    TASKS.reject do |name, desc|
    assigned.any? { |assign| assign.task == name }
    end
  end

where "assigned" is my @current_assignments hash passed by the 
controller.

(credit to James Edward Gray II for the answer)

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