Active record question

rubyonrails-talk
1

I’m not quite sure how to get at this data using Actrive record… I’m trying to get all the appointments made for a particular project. I’m using four models, Projects, Tasks, Resources and Appointments.

The SQL gets me what I’m looking for but how do I do it using Active Record?

Select a.* from appointments a join resources r on r.id = a.resource_id join tasks t on t.id = r.task_id join projects p on p.id = t.project_id Where project_id = 1;

I can get all the Resources for a project using this but can not get the appointments. I could loop through the resources getting all the appointments and tracking them, but that doesn’t seem like the right way to do it. I could also use find_by_sql, but again, that does’t seem right.

class Project < ActiveRecord::Base has_many :tasks belongs_to :customer has_many :resources, :through => :tasks

Any help would be greatly appreciated.

2

Mark Studebaker wrote:

I'm not quite sure how to get at this data using Actrive record.. I'm trying to get all the appointments made for a particular project. I'm using four models, Projects, Tasks, Resources and Appointments.

The SQL gets me what I'm looking for but how do I do it using Active Record?

Select a.* from appointments a join resources r on r.id = a.resource_id join tasks t on t.id = r.task_id join projects p on p.id = t.project_id Where project_id = 1;

Why is project joined in, if project_id comes from tasks?

And why is resources joined in? for its data? It does not participate in the links, right?

I can get all the Resources for a project using this but can not get the appointments. I could loop through the resources getting all the appointmen ts and tracking them, but that doesn't seem like the right way to do it. I could also use find_by_sql, but again, that does't seem right.

class Project < ActiveRecord::Base   has_many :tasks   belongs_to :customer   has_many :resources, :through => :tasks

   Appointment.find( :all, :include => :tasks,                          :conditions => { :'tasks.project_id' => 1} )

In summary, provide enough :has_many => :through to get to the keying table, then put it into your :include and :conditions.

Warning: :include will eager-load, which might slow you down with irrelevant data.

Alternately...

  Task.find_all_by_project_id(1).map(&:appointments).uniq

(-:

3

In a situation like this :joins might be more appropriate - it will write the joins but won't do any of the stuff :include would

Fred

4

In a situation like this :joins might be more appropriate - it will write the joins but won't do any of the stuff :include would

Can you :joins => :leaf_records ? Or do you got to write all the raw SQL?

5

In a situation like this :joins might be more appropriate - it will write the joins but won't do any of the stuff :include would

Can you :joins => :leaf_records ? Or do you got to write all the raw
SQL?

You can either pass raw sql or options in exactly the same format as
include takes them (eg :joins => [{:foo => {:bar =>
[:baz, :bam]}}, :bim])

Fred