On Sunday, February 4, 2018 at 6:25:46 PM UTC-5, Walter Lee Davis wrote:
>
> Even more interesting (to me, anyway) is what happens if you create (but
> don't save) any of these objects:
>
> 2.4.2 :006 > p = Person.new name: 'Walter'
> => #<Person id: nil, name: "Walter", created_at: nil, updated_at: nil>
> 2.4.2 :007 > c = Picture.new file: 'some file'
> => #<Picture id: nil, file: "some file", created_at: nil, updated_at:
> nil>
> 2.4.2 :008 > p.pictures << c
> => #<ActiveRecord::Associations::CollectionProxy [#<Picture id: nil,
> file: "some file", created_at: nil, updated_at: nil>]>
> 2.4.2 :009 > p.save
> (1.9ms) begin transaction
> SQL (23.1ms) INSERT INTO "people" ("name", "created_at", "updated_at")
> VALUES (?, ?, ?) [["name", "Walter"], ["created_at", "2018-02-04
> 23:23:15.342294"], ["updated_at", "2018-02-04 23:23:15.342294"]]
> SQL (0.3ms) INSERT INTO "pictures" ("file", "created_at", "updated_at")
> VALUES (?, ?, ?) [["file", "some file"], ["created_at", "2018-02-04
> 23:23:15.374862"], ["updated_at", "2018-02-04 23:23:15.374862"]]
> SQL (0.4ms) INSERT INTO "person_pictures" ("person_id", "picture_id",
> "created_at", "updated_at") VALUES (?, ?, ?, ?) [["person_id", 2],
> ["picture_id", 2], ["created_at", "2018-02-04 23:23:15.376805"],
> ["updated_at", "2018-02-04 23:23:15.376805"]]
> (1.3ms) commit transaction
> => true
> 2.4.2 :010 >
>
> When you save one of them, all three are saved in order to preserve the
> entire set of relationships.
>
> Walter
>
> > On Feb 4, 2018, at 4:54 PM, Walter Lee Davis <wa...@wdstudio.com
> <javascript:>> wrote:
> >
> > I can't duplicate this finding here. Here's the console log:
> >
> > 2.4.2 :001 > p = Person.new name: 'Walter'
> > => #<Person id: nil, name: "Walter", created_at: nil, updated_at: nil>
> > 2.4.2 :002 > p.save
> > (0.2ms) begin transaction
> > SQL (2.8ms) INSERT INTO "people" ("name", "created_at", "updated_at")
> VALUES (?, ?, ?) [["name", "Walter"], ["created_at", "2018-02-04
> 21:47:31.000973"], ["updated_at", "2018-02-04 21:47:31.000973"]]
> > (1.3ms) commit transaction
> > => true
> > 2.4.2 :003 > c = Picture.new file: 'some file'
> > => #<Picture id: nil, file: "some file", created_at: nil, updated_at:
> nil>
> > 2.4.2 :004 > c.save
> > (0.2ms) begin transaction
> > SQL (2.2ms) INSERT INTO "pictures" ("file", "created_at",
> "updated_at") VALUES (?, ?, ?) [["file", "some file"], ["created_at",
> "2018-02-04 21:47:54.717609"], ["updated_at", "2018-02-04
> 21:47:54.717609"]]
> > (1.4ms) commit transaction
> > => true
> > 2.4.2 :005 > p.pictures << c
> > (0.1ms) begin transaction
> > SQL (0.6ms) INSERT INTO "person_pictures" ("person_id", "picture_id",
> "created_at", "updated_at") VALUES (?, ?, ?, ?) [["person_id", 1],
> ["picture_id", 1], ["created_at", "2018-02-04 21:47:58.847298"],
> ["updated_at", "2018-02-04 21:47:58.847298"]]
> > (1.1ms) commit transaction
> > Picture Load (0.4ms) SELECT "pictures".* FROM "pictures" INNER JOIN
> "person_pictures" ON "pictures"."id" = "person_pictures"."picture_id" WHERE
> "person_pictures"."person_id" = ? LIMIT ? [["person_id", 1], ["LIMIT",
> 11]]
> > => #<ActiveRecord::Associations::CollectionProxy [#<Picture id: 1, file:
> "some file", created_at: "2018-02-04 21:47:54", updated_at: "2018-02-04
> 21:47:54">]>
> > 2.4.2 :006 >
> >
> > Here's the models:
> >
> > class Picture < ApplicationRecord
> > has_many :person_pictures
> > has_many :people, through: :person_pictures
> > end
> >
> > class Person < ApplicationRecord
> > has_many :person_pictures
> > has_many :pictures, through: :person_pictures
> > end
> >
> > class PersonPicture < ApplicationRecord
> > belongs_to :person
> > belongs_to :picture
> > end
> >
> > Whatever is happening on your app is not clear, but you can see that
> after you save the person and the picture, when you add that saved picture
> to the saved person's 'pictures' collection, the only record that gets
> created is a person_picture. Now if either the person or the picture was in
> the "new" state, that is to say, not saved yet, then I could imagine that
> it would be saved by ActiveRecord first in order to allow the
> person_picture record to be saved. Both IDs have to be known before the
> join object can be saved.
> >
> > Walter
> >
> >> On Feb 4, 2018, at 2:30 PM, fugee ohu <fuge...@gmail.com <javascript:>>
> wrote:
> >>
> >> In a has_many_through association where both records exist how do I
> create a new association
> >> In this case Person has_many_pictures through person_picture and I'm
> trying to add an existing picture to an existing person like this:
> >> @person.pictures << @picture
> >> But this creates a new picture instead of adding the association
> >>
> >>
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Since I'm not creating a new picture, only adding existing pictures to a
person I put an update action in the people controller but it tries to
create a new picture and fails with validation :name can't be blank
def add_pictures_update
if (params[:person][:person_id])
@person=Person.find(params[:person][:person_id])
@pictures = Picture.find(params[:person][:picture_ids])
@person.pictures << @pictures
respond_to do |format|
if @person.update
format.html { redirect_to
pictures_path(person_id: params[:picture][:person_id]), notice: 'Person
picture updated.' }
format.json { render :show, status: :created,
location: @picture }
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