Select distinct records from an Array

rubyonrails-talk
1

Hello there, Project is about a personal trainers directory. I would like to create a listing (filter) of available physical exercices to browse the directory by physical exercice.

My Models are :

class PersonalTrainer < User   belongs_to :physical_exercice end

class PhysicalExercice < ActiveRecord::Base   has_many :personal_trainers end

2

I manage to get it the way I wanted using :

@personal_trainers_physical_exercices = PersonalTrainer.find(:all, :select => 'DISTINCT physical_exercice_id')

3

Hugues Brunelle wrote:

I manage to get it the way I wanted using :

@personal_trainers_physical_exercices = PersonalTrainer.find(:all, :select => 'DISTINCT physical_exercice_id')

Why not PhysicalExercice.find :all ?

BTW, note that the English spelling is "exercise".

Best,

4

Hugues Brunelle wrote:

Project is about a personal trainers directory. I would like to create a listing (filter) of available physical exercices to browse the directory by physical exercice.

class PersonalTrainer < User   belongs_to :physical_exercice end

class PhysicalExercice < ActiveRecord::Base   has_many :personal_trainers end

I have a feeling that what you're really going to want here is a many-to-many association rather than a one-to-many.

I get this feeling because of how your current associations read: "Personal trainer belongs to a physical exercice." While technically accurate as far as Rails relationships go. I would not say that a person belongs to an exercice. This makes me think these two are not so directly associated.

So I would then consider this: "A physical exercice may have many personal trainers. Each personal trainer can instruct in many physical exercices through qualification."

class PersonalTrainer < User   has_many :qualifications   has_many :physical_exercices, :through => :qualifications end

class PhysicalExercice < ActiveRecord::Base   has_many :qualifications   has_many :personal_trainers, :through => :qualifications end

class Qualification < ActiveRecord::Base   belongs_to :personal_trainer   belongs_to :physical_exercice end

Now PhysicalExcercice.all will return a unique list of exercices regardless of how many personal trainers are qualified to instruct in the exercise. The new Qualification model will track which trainers are qualified on which exercices.

personal_trainer = PersonalTrainer.first personal_trainer.physical_exercices     * Athlétisme (100m)     * Badminton     * Boxe     * Conditionnement physique

physical_exercice = PhysicalExercice.first physical_exercice.personal_trainers     * Bill     * Steve     * Frank

Note: I'm only guessing at your needs, but I have a feeling that this is really what you're intending.

5

Why not PhysicalExercice.find :all ?

Because some PhysicalExercise don't have any PersonalTrainer offering it as a main speciality. Since I want to filter by PhysicalExercise, I want to be sure that it doen't return a nil value.

BTW, note that the English spelling is "exercise".

You're right about Exercise, thanks for pointing that out. Will make the correction.

Hugues

6

Robert Walker wrote:

Hugues Brunelle wrote:

Project is about a personal trainers directory. I would like to create a listing (filter) of available physical exercices to browse the directory by physical exercice.

class PersonalTrainer < User   belongs_to :physical_exercice end

class PhysicalExercice < ActiveRecord::Base   has_many :personal_trainers end

I have a feeling that what you're really going to want here is a many-to-many association rather than a one-to-many.

I get this feeling because of how your current associations read: "Personal trainer belongs to a physical exercice." While technically accurate as far as Rails relationships go. I would not say that a person belongs to an exercice. This makes me think these two are not so directly associated.

So I would then consider this: "A physical exercice may have many personal trainers. Each personal trainer can instruct in many physical exercices through qualification."

class PersonalTrainer < User   has_many :qualifications   has_many :physical_exercices, :through => :qualifications end

class PhysicalExercice < ActiveRecord::Base   has_many :qualifications   has_many :personal_trainers, :through => :qualifications end

class Qualification < ActiveRecord::Base   belongs_to :personal_trainer   belongs_to :physical_exercice end

Now PhysicalExcercice.all will return a unique list of exercices regardless of how many personal trainers are qualified to instruct in the exercise. The new Qualification model will track which trainers are qualified on which exercices.

personal_trainer = PersonalTrainer.first personal_trainer.physical_exercices     * Athlétisme (100m)     * Badminton     * Boxe     * Conditionnement physique

physical_exercice = PhysicalExercice.first physical_exercice.personal_trainers     * Bill     * Steve     * Frank

Note: I'm only guessing at your needs, but I have a feeling that this is really what you're intending.

First of all thank you for your time.

The many-to-many association is one task I need to do soon. The original concept was to categorize each PersonalTrainer with ONE PhysicalExercise to avoid PersonalTrainers to select all PhysicalExercise. I will make a main (ONE) and a secondary (MANY) PhysicalExercise for PersonalTrainer.

Soon I will try what you suggest.

Thanks again and I might write to you again.

Regards,

Hugues

7

Hugues Brunelle wrote:

Why not PhysicalExercice.find :all ?

Because some PhysicalExercise don't have any PersonalTrainer offering it as a main speciality. Since I want to filter by PhysicalExercise, I want to be sure that it doen't return a nil value.

PhysicalExercice.find :all, :conditions => "personal_trainer_id IS NOT NULL"

8

PhysicalExercice.find :all, :conditions => "personal_trainer_id IS NOT NULL"

Actually I do not have a personal_trainer_id but as soon as I make an upgrade for the many-to-many association, I'll be able to try it.

Thx a lot for your help :slight_smile: