Printing nested data to screen

rubyonrails-talk
1

I have a table called people_skills linked to a people table by a FK named people_id. Trying to get the people_skills fields printed on a "Show" screen has never given me what I wanted (the field value) without resorting to a helper which forms an input box. The people table's values are printed but the results of the people_skills are either non-existent or strange (e.g. #<ActiveRecord::Relation: 0x1d12778>). This is the controller code (people_controller.rb):

def show     @person = Person.find(params[:id])

    @people_skill = PeopleSkill.select('skill').where(":people_id = @person.id")     show_skill = @people_skill.build.skill     yrs_exp = @people_skill.build.years_of_experience

    respond_to do |format|       format.html # show.html.erb       format.xml { render :xml => @person, :xml => @peopleskill }     end   end

and this is the show.html.erb:

<p>   <b>Skill</b>   <%= @people_skill.build.skill %>   <%= PeopleSkill.where("people_id = @person.id")%> </p>

which produced the strange #<ActiveRecord... output above. Other guesses have either given me errors or no output at all, so please tell me the right way to do this.              Barney

2

Barney <bsperlin@...> writes:

<p>   <b>Skill</b>   <%= @people_skill.build.skill %>   <%= PeopleSkill.where("people_id = @person.id")%> </p>

which produced the strange #<ActiveRecord... output above. Other guesses have either given me errors or no output at all, so please tell me the right way to do this.              Barney

PeopleSkill.where("people_id = @person.id") will return an ActiveRecord relation object, rather that execute the query againstg the database. Try: PeopleSkill.where("people_id = @person.id").find

3

Thanks Andrew, but I couldn't make the 'find' work on the 'PeopleSkill.where...' line. When I used 'find' on the @people_skill line it came very close (since in the controller, listed above, people_skill was already choosing the field 'skill'), so when I used: <%= @people_skill.find(@person.id) and skipped the next line listed above, the SQLException was SQLite3::SQLException: near ".": syntax error: SELECT skill FROM "people_skills" WHERE "people_skills"."id" = 23 AND (:people_id = @person.id) LIMIT 1 which is VERY close to what I want, except that I want "people_skills"."people_id"=23, not "people_skill"."id"=23. I know that 'find' always looks for the 'id' so I've got to get a different variation. What changes should I make?      Thanks again,             Barney

4

Barney <bsperlin@...> writes:

Thanks Andrew, but I couldn't make the 'find' work on the 'PeopleSkill.where...' line. When I used 'find' on the @people_skill line it came very close (since in the controller, listed above, people_skill was already choosing the field 'skill'), so when I used: <%= @people_skill.find(@person.id) and skipped the next line listed above, the SQLException was SQLite3::SQLException: near ".": syntax error: SELECT skill FROM "people_skills" WHERE "people_skills"."id" = 23 AND (:people_id = @person.id) LIMIT 1 which is VERY close to what I want, except that I want "people_skills"."people_id"=23, not "people_skill"."id"=23. I know that 'find' always looks for the 'id' so I've got to get a different variation. What changes should I make?      Thanks again,             Barney

What if we flip the logic?

Assuming your models look something like:

Person < ActiveRecord::Base   has_and_belongs_to_many :skills end

Skill < ActiveRecord::Base   has_and_belongs_to_many :people end

With the appropriate PeopleSkills join table in the database.

Then:

@person = Person.find(params[:id]) @people_skill = @person.skills

Or more easily:

def show     @person = Person.find(params[:id]) end

and the view becomes:

<p>   <b>Skills</b>   <%= @people.skills > </p>

or similar.

5

The original code didn’t work because Barney was generating an ActiveRecord Relation. The .find almost worked, except he wanted to embed Ruby code in a SQL statement. This should do it:

PeopleSkill.where(“people_id = #{@person.id}”).find

In the future, I think something like Andrew’s suggestion would be a lot more readable and maintainable–I.E. using ActiveRecord to convert your database information into objects, and looking for your information among the objects instead of at the database level.

6

Hi Andrew,      Currently "show" works from the listings page but "new" and "edit" don't. The current people_controller is:

def show     @person = Person.find(params[:id])

    @people_skills = PeopleSkill.all

    @people_skill = PeopleSkill.select('skill').where("{person_id => @person.id}")

    respond_to do |format|       format.html # show.html.erb       format.xml { render :xml => @person, :xml => @peopleskill }     end   end

and the people_skills_controller.rb#show is:

def show     @people_skill = PeopleSkill.find(params[:id])

    respond_to do |format|       format.html # show.html.erb       format.xml { render :xml => @people_skill }     end   end

The people_controller.rb#edit, which doesn't work, is:

def edit     @person = Person.find(params[:id])

    @people_skills = PeopleSkill.all

    @people_skill = PeopleSkill.select('skill').where("{person_id => @person.id}")

    respond_to do |format|       format.html # show.html.erb       format.xml { render :xml => @person, :xml => @peopleskill }     end   end

and the people_skills_controller.rb#edit is:

def edit     @people_skill = PeopleSkill.select("skill").where("{person_id => @person.id}") #find(params[:person_id])

    respond_to do |format|       format.html # show.html.erb       format.xml { render :xml => @people_skill }     end   end

and these give an error in the \people_skills\_form.html.erb at the first line:

%= form_for(@people_skill) do |f| %>   <% if @people_skill.errors.any? %>

which is: undefined method `model_name' for ActiveRecord::Relation:Class and if I cut one @people_skill out of a controller I get: undefined method `model_name' for NilClass:Class

and I take these both to mean that @people_skill doesn't exist. Could the 2 @people_skill instances be colliding? Or the second shadowing the first?

Any further help would be appreciated and I know you've put more into this than you need to!                 Barney

7

Hi Eric,

Well, I couldn't make the objects work:

@people_skill = @person.skill

wasn't accepted. I'll keep trying and any suggestions are appreciated.        Barney

8

Barney <bsperlin@...> writes:

The people_controller.rb#edit, which doesn't work, is:

def edit     @person = Person.find(params[:id])

    @people_skills = PeopleSkill.all

    @people_skill = PeopleSkill.select('skill').where("{person_id => @person.id}")

    respond_to do |format|       format.html # show.html.erb       format.xml { render :xml => @person, :xml => @peopleskill }     end   end

and the people_skills_controller.rb#edit is:

def edit     @people_skill = PeopleSkill.select("skill").where("{person_id => @person.id}") #find(params[:person_id])

    respond_to do |format|       format.html # show.html.erb       format.xml { render :xml => @people_skill }     end   end

and these give an error in the \people_skills\_form.html.erb at the first line:

%= form_for(@people_skill) do |f| %>   <% if @people_skill.errors.any? %>

which is: undefined method `model_name' for ActiveRecord::Relation:Class and if I cut one @people_skill out of a controller I get: undefined method `model_name' for NilClass:Class

and I take these both to mean that @people_skill doesn't exist. Could the 2 @people_skill instances be colliding? Or the second shadowing the first?

Any further help would be appreciated and I know you've put more into this than you need to!                 Barney

Again, the controller is returning a *relation*, rather than the actual results. Try changing:

@people_skill = PeopleSkill.select('skill').where("{person_id => @person.id}")

to

@people_skill = PeopleSkill.select('skill').where("{person_id => @person.id}").all

Essentially this tells rails you are finished building the query and are prepared for results - it will trigger a query against database.

I still can't help feeling you are experiencing these issues because you are starting to swim upstream against the rails conventions. When things seem difficult, there is usually some ruby voodoo missing. Knowing how to work ruby and rails magic involves learning all the spells.

If you are still having difficulty, please post you model logic as well - especially the relationships between the objects (belongs_to, has_many, etc)

9

I still can't help feeling you are experiencing these issues because you are starting to swim upstream against the rails conventions.

One of the unspoken conventions being violated is putting Queries in the Controller - :frowning:

If you are still having difficulty, please post you model logic as well - especially the relationships between the objects (belongs_to, has_many, etc)

This is a really good suggestion. Spending time expressing the logic and what your purpose is will increase the quality of help that you get - and likely reduce frustration.

10

Hi Andrew and Curtis,      I've been away for 3 days but have come back to the problem above.         As things have continued to be difficult I have backed off keeping things well normalized and have crunched the people_skills table, with its 3 fields of: skill, competency and years of experience, into the people table. This still leaves another table, employee_infos, in a one-one relationship with people which is still not printing on the same screen as people. Here are the models in question:

class Person < ActiveRecord::Base   default_scope :order => 'last_name'   has_one :EmployeeInfo   has_one :CandidateInfo   has_one :EmploymentHistory

  validates :first_name, :presence => true   validates :last_name, :presence => true   validates :email, :presence => true end

class EmployeeInfo < ActiveRecord::Base   belongs_to :person end

The people_controller.rb#index, where I want to see the proper data, is:

def index     @people = Person.all     @employee_infos = EmployeeInfo.all

    respond_to do |format|       format.html # index.html.erb       format.xml { render :xml => @people }     end   end

And a relevant section of index.html.erb is: <%= @people.each do |person| %>   <tr> ...     <td><%= person.zip_code %></td>     <td><%= person.skill_set %></td>     <td><%= WHAT GOES HERE TO BE ABLE TO PRINT THE "position" FIELD OF THE employee_infos TABLE? WHAT CHANGES SHOULD BE MADE TO THE ABOVE?

     A second point was made about not having SQL statements in the controller (which I have done) so what is the alternative? What pages can I go to to see some examples of the right way?      Thanks again,           Barney

11

Barney <bsperlin@...> writes:

And a relevant section of index.html.erb is: <%= @people.each do |person| %>   <tr> ...     <td><%= person.zip_code %></td>     <td><%= person.skill_set %></td>     <td><%= WHAT GOES HERE TO BE ABLE TO PRINT THE "position" FIELD OF THE employee_infos TABLE? WHAT CHANGES SHOULD BE MADE TO THE ABOVE?

If I am reading this right:

<td><%= person.employee_info.position %></td>

Note: this will trigger a database query to match the record in employee_info with the person's ID. Your @employee_infos variable is not being touched.
You really want eager load:

@people = Person.all.include(:employee_info)

     A second point was made about not having SQL statements in the controller (which I have done) so what is the alternative? What pages can I go to to see some examples of the right way?

The seminal blog post was this http://weblog.jamisbuck.org/2006/10/18/skinny- controller-fat-model