Simple association question

Rails
1

I have two models, Donor and Contribution, and have has_many and
belongs_to set respectively.

My question is regarding creation of associated objects. I’ll let the
code speak:

me = Donor.find(1)
contribution = me.contributions.create do |e|
e.amount = 164.00
e.category = Category.find(1)
end

I thought this was valid, but it doesn’t work properly - it appears to
create a new Contribution, but does not associate it with the Donor
(me). So, I tried this (using the build method):

contribution = me.contributions.build do |e|
e.amount = 164.00
e.category = Category.find(1)
e.save
end

This appears to have associated the object, but the contribution has no
values for the amount or category. Finally, I tried this (using the new
method):

contribution = me.contributions.new do |e|
e.donor = me
e.amount = 164.00
e.category = Category.find(1)
e.save
end

This does work, but I thought I could skip having to set the
association manually (shouldn’t the donor be inferred through the chain
me.contributions?)

Any help on this would be greatly appreciated - I’d just like to know if
I am assuming too much about the associations.

2

I don’t think create() accepts a block. I would do:

me = Donor.find(1)
me.contributions.create( { :amount => 164.00, :category =>
Category.find(1) } )

3

You could also do:

my_contrib = Contribution.new
my_contrib.amount - 164.00
my_contrib.category = Category.find(1)

me = Donor.find(1)
me.contributions << my_contrib