I can’t even find documentation on how to use the do_block on an
association. I’d like to know why it doesn’t work what I am trying to
do. Any help appreciated.
has_many :children, dependent: :destroy, -> { order ‘id asc’ } do
This line looks wrong to me. You have a lambda arrow (-> with it’s block
{ … } and immediately trying to open another block with do. Written a
slightly different way it might look something like:
has_many :children, dependent: :destroy, -> do order ‘id asc’ end do
It’s interesting, because this line:
has_many :children, -> { order ‘id asc’ } do
works fine (except at destroying associated records, of course), so it
seems it’s not a problem with two blocks, right?
Here’s an example that maybe shows what you’re trying to do:
has_many :tracks, -> { order “position” }, dependent: :destroy
In this case it appear to me the lambda function is in the “scope”
argument with options following and no block.
I don’t understand what you mean with this, did you miss the “do” at the
end of the line. Anyways, I tried the order I think you are suggesting:
has_many :children, -> { order ‘id asc’ }, dependent: :destroy do
with no luck. So it seems that I have to choose between having 2 out of
the 3 things I need.
has_many :children, dependent: :destroy, -> { order ‘id asc’ } do
but this raises an error:
SyntaxError in ParentsController#index
has_many :children, dependent: :destroy, -> { order ‘id asc’ } do
This line looks wrong to me. You have a lambda arrow (-> with it’s block
{ … } and immediately trying to open another block with do. Written a
slightly different way it might look something like:
has_many :children, dependent: :destroy, -> do order ‘id asc’ end do
Here’s an example that maybe shows what you’re trying to do:
has_many :tracks, -> { order “position” }, dependent: :destroy
In this case it appear to me the lambda function is in the “scope”
argument with options following and no block.
In general if you have a “do” you need an “end”, although sometimes ruby
interprets the end of your block for you. (but generally it is good
practice to always end a “do” with an “end”)
Your discrepancy (and confusion) has to do with the way has_many is
receiving arguments.
In Rails 4, the second parameter is scope (in rails 3, the second
parameter was options)
has_many :children, dependent: :destroy, → { order ‘id asc’ } do
thanks for your answer. The link you provided was useful.
In general if you have a “do” you need an “end”,
It does have an end, I left it out of the reply because it is in the
first post. The complete statement I’d like to have would be:
has_many :children, → { order ‘id asc’ }, dependent: :destroy do
def persisted
collect { |a| a if a.persisted? }
end
end
What I’m trying to do is briefly mentioned in the page you referenced
(has_many (ActiveRecord::Associations::ClassMethods) - APIdock)
but there is no link to further documentation or examples. I just would
need to add the scope to the example, from:
has_many :children, :dependent => :destroy do
def at(time)
proxy_owner.children.find_with_deleted :all, :conditions => [
“created_at <= :time AND (deleted_at > :time OR deleted_at IS
NULL)”, { :time => time }
]
end
end
to
has_many :children, → { order “posted_on” }, :dependent => :destroy do
(rest of the code)
but this is not covered in THAiSi’s note. I think this is very useful,
and should be easier to find documentation.
