-i searched through the news group but couldn’t find the answer for my
problem.
example:
----------- classes ----------
class Car < ActiveRecord::Base
has_one :colour
def after_create()
colour = Colour.new
colour.name = ‘colour1’
colour.save
end
end
class Chair < ActiveRecord::Base
has_one :colour
end
class Colour < ActiveRecord::Base
end
-------------- tables ---------
create table cars(id int PRIMARY KEY NOT NULL AUTO_INCREMENT,name
varchar(50),colour_id int NOT NULL, primary key(id));
create table chairs(id int PRIMARY KEY NOT NULL AUTO_INCREMENT,name
varchar(50),colour_id int NOT NULL);
create table colours(id int PRIMARY KEY NOT NULL AUTO_INCREMENT,name
varchar(50));
- i consider it a many to one relation because diferent types of items
are refering to one type (Car and Chair both have colour).
- i wrote the models as above i create a Car object, i save it but
alwayes my colour_id in the database remains 0.
I would appreciate if your could give me a hint.
Hi
I’m absolutely not an expert in this, but I would have expected:
class Colour < ActiveRecord::Base
belongs_to :chair
belongs_to :car
end
I think that with a has_one relation, you require a belongs_to on the
other side of the relation.
Darren
P. Pantouffe wrote:
-i searched through the news group but couldn’t find the answer for my
problem.
example:
----------- classes ----------
class Car < ActiveRecord::Base
has_one :colour
def after_create()
colour = Colour.new
colour.name = ‘colour1’
colour.save
end
end
class Chair < ActiveRecord::Base
has_one :colour
end
class Colour < ActiveRecord::Base
end
-------------- tables ---------
create table cars(id int PRIMARY KEY NOT NULL AUTO_INCREMENT,name
varchar(50),colour_id int NOT NULL, primary key(id));
create table chairs(id int PRIMARY KEY NOT NULL AUTO_INCREMENT,name
varchar(50),colour_id int NOT NULL);
create table colours(id int PRIMARY KEY NOT NULL AUTO_INCREMENT,name
varchar(50));
- i consider it a many to one relation because diferent types of items
are refering to one type (Car and Chair both have colour).
- i wrote the models as above i create a Car object, i save it but
alwayes my colour_id in the database remains 0.
I would appreciate if your could give me a hint.
Hi
In addition to this, isn’t the relation you require in both cases a
has_many, i.e. both chairs and cars have many colours, and a colour
belongs to a chair or a car?
Darren
P. Pantouffe wrote:
Hi and tkns for the reply
i’ve tried with:
class Colour < ActiveRecord::Base
belongs_to :chair
belongs_to :car
end
and modified after_create
def after_create()
colour = Colour.new
colour.name = ‘colour1’
colour.save
save() # <- this one
end
my colour_id still remains 0.
- i’m beginner in both databases and ruby. I interpret a has_many
relation as a parent_id colour for the colours table and i don’t think
this is correct.
There’s something wrong in what i’m doing but I don’t know what. 
ALthough the english doesn’t always read well, the belongs_to goes where
the foreign key is.
In your case, thats Car or CHair. So
Car belongs_to Color, Color has_many Cars
Chair belongs_to COlor, Color has_many Chairs
As I said you would say a “Car belongs to a colour” in english, but
thats how you say it in rails 
A.
Hi and tkns for the reply
i’ve tried with:
class Colour < ActiveRecord::Base
belongs_to :chair
belongs_to :car
end
and modified after_create
def after_create()
colour = Colour.new
colour.name = ‘colour1’
colour.save
save() # <- this one
end
my colour_id still remains 0.
- i’m beginner in both databases and ruby. I interpret a has_many
relation as a parent_id colour for the colours table and i don’t think
this is correct.
There’s something wrong in what i’m doing but I don’t know what.
Alan F. wrote:
ALthough the english doesn’t always read well, the belongs_to goes where
the foreign key is.
In your case, thats Car or CHair. So
Car belongs_to Color, Color has_many Cars
Chair belongs_to COlor, Color has_many Chairs
As I said you would say a “Car belongs to a colour” in english, but
thats how you say it in rails
A.
Sorry, that should have been “you wouldn’t say…in english”, and
there probably shouldn’t be quite so many capital letters.
Alan
P. Pantouffe wrote:
Hi and tkns for the reply
i’ve tried with:
class Colour < ActiveRecord::Base
belongs_to :chair
belongs_to :car
end
and modified after_create
def after_create()
colour = Colour.new
colour.name = ‘colour1’
colour.save
save() # <- this one
end
my colour_id still remains 0.
- i’m beginner in both databases and ruby. I interpret a has_many
relation as a parent_id colour for the colours table and i don’t think
this is correct.
There’s something wrong in what i’m doing but I don’t know what.
I take it you mean the colour_id of your new Car remains unchanged?
This is what I would expect to happen given the code above, although it
will create an entry in the colour table. What you haven’t done is tie
the two records together.
RoR does a lot of nice things for you, like make associations appear as
if they are in the original model. What does this mean? When your
creating a new Car, try:
new_car = Car.new
new_car.colour = Colour.find_or_create_by_name “colour 1”
new_car.save
(I am no expert either, but I figure hanging out here and trying to
solve problems I will learn)
Hi, thank u for anserwing me.
Indeed it works when i say car belongs to color (David must hove some
reason for switching it.) and putting the color creation code in a way
askegg wrote.
- it don’t understand why my code in the after_create() method did not
work, the API says that ,after_create() is called after Base.save on
new objects that haven’t been saved yet (no record exists)", in the
code:
def after_create()
colour = Colour.new
colour.name = ‘colour1’
…
end
colour is the Atribute, isn’t it?
P. Pantouffe wrote:
Hi, thank u for anserwing me.
Indeed it works when i say car belongs to color (David must hove some
reason for switching it.) and putting the color creation code in a way
askegg wrote.
- it don’t understand why my code in the after_create() method did not
work, the API says that ,after_create() is called after Base.save on
new objects that haven’t been saved yet (no record exists)", in the
code:
def after_create()
colour = Colour.new
colour.name = ‘colour1’
…
end
colour is the Atribute, isn’t it?
Then that would need to be @colour. You just created a brand new
temporary variable.
A.
- it don’t understand why my code in the after_create() method did not
work, the API says that ,after_create() is called after Base.save on
new objects that haven’t been saved yet (no record exists)", in the
code:
A record doesn’t have an ID until it’s be saved.
So if you save the child before the parent, the parent_id column
(colour_id) will be zero by default.
Alan F. wrote:
def after_create()
colour = Colour.new
colour.name = ‘colour1’
…
end
colour is the Atribute, isn’t it?
Then that would need to be @colour. You just created a brand new
temporary variable.
@colour = Colour.create(…) would do the trick. But the other way is
better
A.
thank u all for the info.
Best wishes!
P. Pantouffe wrote:
colour is the Atribute, isn’t it?
The code is called after the record is created, but the current code
creates a new entry in the colour table, but does not tie it to the Car
record.
Strictly speaking, their is no “colour” attribute on the Car object -
there is only an association to a Colour object, so you need to pass a
Colour object not a string.
class Car < ActiveRecord::Base
belongs_to :colour
def after_create()
self.colour = Colour.find_or_create_by_name(‘colour 1’)
self.save
end
end