Question about saving

Hi,

I have a couple of classes, defined in simplified form as follows:

class Item < ActiveRecord::Base
  has_many :item_properties, :dependent => :delete_all
end

class ItemProperty < ActiveRecord::Base
  belongs_to :item
  before_save :clean_up
end

When creating a new instance of Item, things work fine - I create an
Item object, add some ItemProperty objects to it:

item.item_properties << ItemProperty.new(...)

and save it at the end by calling item.save. Part of validation is
done in 'item', because ItemProperty objects themselves do not have
enough information to perform full validation (for example, to make
sure certain ItemProperties do not co-exist in the same Item object).
When creating, this works fine, because if validation fails, the item
isn't created.

When updating, however - and I understand this is by design - things
don't work well. If I update an Item object by adding another
ItemProperty:

item.item_properties << ItemProperty.new(...)

ItemProperty is immediately saved into the database, even without
a .save. Note that the contents of Item.item_properties can vary
between updates - meaning, changing the ItemProperty object itself,
instead of rebuilding the list of ItemProperty objects is not an
option.

To make a long story short, when updating an existing object, I need
to be able to add as many ItemProperty objects as necessary, and I
would like no child objects to be saved, until item.save is called -
because I need the validation in Item to intercept any potential
issues. Is it possible to delay saving when adding objects to a
has_many association, until .save is called (like when creating a new
object)? If not, what are my options?

I appreciate any help. Thanks

I achieved the needed result by using collection.build, and using a
before_update callback to delete all rows from item_properties with
matching item_id. Still, it feels like a hack, and if anyone has a
better suggestion, I'd appreciate some feedback. Thanks

Hi,

I have a couple of classes, defined in simplified form as follows:

class Item < ActiveRecord::Base
has_many :item_properties, :dependent => :delete_all
end

class ItemProperty < ActiveRecord::Base
belongs_to :item
before_save :clean_up
end

When creating a new instance of Item, things work fine - I create an
Item object, add some ItemProperty objects to it:

item.item_properties << ItemProperty.new(...)

and save it at the end by calling item.save. Part of validation is
done in 'item', because ItemProperty objects themselves do not have
enough information to perform full validation (for example, to make
sure certain ItemProperties do not co-exist in the same Item object).
When creating, this works fine, because if validation fails, the item
isn't created.

Is it not possible to put the validation currently done in Item into
ItemProperty? You say that the ItemProperty object does not have the
information, but it does have access to its parent Item so you may be
able to access this and fail the validation if appropriate. This
would prevent the save.

When updating, however - and I understand this is by design - things
don't work well. If I update an Item object by adding another
ItemProperty:

item.item_properties << ItemProperty.new(...)

ItemProperty is immediately saved into the database, even without
a .save. Note that the contents of Item.item_properties can vary
between updates - meaning, changing the ItemProperty object itself,
instead of rebuilding the list of ItemProperty objects is not an
option.

I don't understand this point.

Colin