Messed-up habtm relationship

Rails
#1

Hi,

I have a many-to-many relationship between dishes and ingredients

class Dish < ActiveRecord::Base
has_and_belongs_to_many :ingredients
end

class Ingredient < ActiveRecord::Base
has_and_belongs_to_many :dishes
end

I have a join table dishes_ingredients

now when i access my_dish.ingredients, i get a list of what looks like
Ingredient objects, but the but they don’t have the right attributes:

#<Ingredient:0x29d3544 @readonly=true, @attributes={“name”=>“Chicken”,
“ingredient_id”=>“36”, “dish_id”=>“1”, “id”=>“1”}>

The join table’s columns ‘dish_id’ and ‘ingredient_id’ show up, and the
id is the id of the row in the join table, not the one of the ingredient
(Chicken).

I noticed this because the following was false where it should have been
true:

my_dish.ingredients.include?(chicken)

Ingo

#2

I think you may have confused what include? does.

The description (Ruby doc) is:

Returns true if any member of enum equals obj. Equality is tested using
==.

When testing your Ingredient objects for equality, unless you have
specifically overridden == in your model, what’s being compared to
‘Chicken’
is actually an object of type Ingredient.

Consider:

my_dish.ingredients.find{|ingredient| ingredient.name == ‘Chicken’}

I’m pretty sure there’s a better way to do this, but find is always
reliable.

Hope this helps.

Keynan P. wrote:

class Ingredient < ActiveRecord::Base

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#3

I found what the problem was: I had accidentally given the
dishes_ingredients join table an ‘ID’ column, and this was messing
things up.

Thanks for all your help!

Ingo

#4

Thanks, Ross!

Actually, in my example the variable ‘chicken’ is thought to contain a
‘Ingredient’ object. So I should have written:

my_dish = Dish.find(:first)
chicken = Ingredient.find_by_name(“Chicken”)
my_dish.ingredients.include?(chicken)

That should work, or? But it doesn’t!

Ingo

Steve R. wrote:

I think you may have confused what include? does.

The description (Ruby doc) is:

Returns true if any member of enum equals obj. Equality is tested using
==.

When testing your Ingredient objects for equality, unless you have
specifically overridden == in your model, what’s being compared to
‘Chicken’
is actually an object of type Ingredient.

Consider:

my_dish.ingredients.find{|ingredient| ingredient.name == ‘Chicken’}

I’m pretty sure there’s a better way to do this, but find is always
reliable.

Hope this helps.

Keynan P. wrote:

class Ingredient < ActiveRecord::Base

–
Posted via http://www.ruby-forum.com/.

–
View this message in context:
http://www.nabble.com/-Rails--messed-up-habtm-relationship-tf2627404.html#a7332184
Sent from the RubyOnRails Users mailing list archive at Nabble.com.