how to 'delete' an object from an association collection in-memory only

rubyonrails-talk
1

Hi,

My Rails app offers opportunities to try out models on a 'what-if' basis, where dependent associations can be modified to obtain alternative results for the parent. Is there a way to delete/destroy the member of a collection so that I can play around with the accordingly modified parent in memory, without actually committing the destruction of the collection member to the data store? Based on my read of the docs, there is no 'delete' counterpart to 'collection.build' for association members.

Thanks for any comment,

Lille

2

If I understand you correctly you only need to remove the association's array element. That will not delete the underlying DB record if there is one.

3

Lille wrote in post #965224:

Hi,

My Rails app offers opportunities to try out models on a 'what-if' basis, where dependent associations can be modified to obtain alternative results for the parent. Is there a way to delete/destroy the member of a collection so that I can play around with the accordingly modified parent in memory, without actually committing the destruction of the collection member to the data store? Based on my read of the docs, there is no 'delete' counterpart to 'collection.build' for association members.

If it were my app, I think I'd do this differently: start a transaction for the "what if" stuff, then either roll it back or commit it when done.

Thanks for any comment,

Lille

Best,

4

Hi,

I'm not sure why you are worried about touching the data store. collection.build doesn't save the new object so there is nothing in the db that could be deleted. If all you want to do is revert collection.build just remove that element of the association array (as pepe pointed out).

comment = @post.comments.build @post.comments.delete(comment)

or

@post.comments.build @post.comments.delete(@post.comments.last)

Hope this helps!

Simon