# Anyone know how to copy rows?

**URL:** <https://www.ruby-forum.com/t/anyone-know-how-to-copy-rows/58486>\
**Category:** Rails\
**Created:** [April 22, 2006, 2:38am UTC](https://www.ruby-forum.com/t/anyone-know-how-to-copy-rows/58486 "2006-04-22T02:38:15Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![sprsquish](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/d9b06d/32.png) [@sprsquish](https://www.ruby-forum.com/u/sprsquish)\
**Post date:** [April 22, 2006, 2:38am UTC](https://www.ruby-forum.com/t/anyone-know-how-to-copy-rows/58486/1 "2006-04-22T02:38:15Z")

</div>

Hey all,

I’m trying to write something that allows one to copy several rows from  
a table and create new rows based on those rows. This will be used to  
intentionally duplicate rows. Did I mention that I was having little  
luck? I’m from a PHP world, but I’ve been getting really into Rails  
lately.

Here’s what I’ve got(assume an event has\_many wastes):

def wastePrepopulate  
@wastes = Waste.find\_all  
@wastes.each do |waste|  
Event.find(params[:id]).wastes.create(params[:waste])  
end  
flash[:notice] = ‘The records have been prepopulated.’  
redirect\_to :action =\> “showwastes”, :id =\>params[:id]  
end

If I feed parameters to it using a form, it will create new records with  
those parameters, but I can’t get it to use the data from  
@wastes=Waste.find\_all.

I’m ultimately trying to set up a way to create records based on  
existing data. Any help would be GREATLY appreciated.

Cheers,  
Monkey

---

<div class="post-metadata">

**Author:** ![sprsquish](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/d9b06d/32.png) [@sprsquish](https://www.ruby-forum.com/u/sprsquish)\
**Post date:** [April 22, 2006, 3:03am UTC](https://www.ruby-forum.com/t/anyone-know-how-to-copy-rows/58486/2 "2006-04-22T03:03:05Z")

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jeff stevens wrote:

> Hey all,
> 
> I’m trying to write something that allows one to copy several rows from  
> a table and create new rows based on those rows. This will be used to  
> intentionally duplicate rows. Did I mention that I was having little  
> luck? I’m from a PHP world, but I’ve been getting really into Rails  
> lately.
> 
> Here’s what I’ve got(assume an event has\_many wastes):
> 
> def wastePrepopulate  
> @wastes = Waste.find\_all  
> @wastes.each do |waste|  
> Event.find(params[:id]).wastes.create(params[:waste])  
> end  
> flash[:notice] = ‘The records have been prepopulated.’  
> redirect\_to :action =\> “showwastes”, :id =\>params[:id]  
> end
> 
> If I feed parameters to it using a form, it will create new records with  
> those parameters, but I can’t get it to use the data from  
> @wastes=Waste.find\_all.
> 
> I’m ultimately trying to set up a way to create records based on  
> existing data. Any help would be GREATLY appreciated.
> 
> Cheers,  
> Monkey

Something like this should work

@event = Event.find(params[:id])  
@wastes = Waste.find\_all  
@wastes.each do |waste|  
data = waste.attributes.reject do |key, value|  
key == :id ||  
key == :event\_id  
end  
@event.wastes.create(data)  
end

First, you don’t to do “Event.find(params[:id])” in a loop since the  
result will be the same every time, so sense adding that DB strain.

Second, active record objects have an “attributes” method that dumps  
their data to a hash. We take that hash and reject the keys we don’t  
want duplicated, in this case the id, since the new rows should have new  
ids, and event\_id, since we want the new wastes to be associated with  
the event we are calling create on.

---

<div class="post-metadata">

**Author:** ![sprsquish](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/d9b06d/32.png) [@sprsquish](https://www.ruby-forum.com/u/sprsquish)\
**Post date:** [April 23, 2006, 4:05am UTC](https://www.ruby-forum.com/t/anyone-know-how-to-copy-rows/58486/3 "2006-04-23T04:05:19Z")

</div>

Is there something here I’m missing? Why not use ActiveRecord’s .clone  
method? From [api.rubyonrails.org](http://api.rubyonrails.org):

“Returns a clone of the record that hasnâ??t been assigned an id yet and  
is treated as a new record. Note that this is a “shallow” clone: it  
copies the objectâ??s attributes only, not its associations. The extent of  
a “deep” clone is application-specific and is therefore left to the  
application to implement according to its need.”

So, if you wanted to copy every row of a table, you could call clone on  
every row and save those returned copies.

---

<div class="post-metadata">

**Author:** ![sprsquish](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/d9b06d/32.png) [@sprsquish](https://www.ruby-forum.com/u/sprsquish)\
**Post date:** [April 23, 2006, 8:10pm UTC](https://www.ruby-forum.com/t/anyone-know-how-to-copy-rows/58486/4 "2006-04-23T20:10:44Z")

</div>

Bryan D. wrote:

> Is there something here I’m missing? Why not use ActiveRecord’s .clone  
> method? From [api.rubyonrails.org](http://api.rubyonrails.org):
> 
> “Returns a clone of the record that hasnâ??t been assigned an id yet and  
> is treated as a new record. Note that this is a “shallow” clone: it  
> copies the objectâ??s attributes only, not its associations. The extent of  
> a “deep” clone is application-specific and is therefore left to the  
> application to implement according to its need.”
> 
> So, if you wanted to copy every row of a table, you could call clone on  
> every row and save those returned copies.

Heh, didn’t AR had that.

so you can probably rewrire my code as:

@event = Event.find(params[:id])  
@wastes = Waste.find\_all  
@wastes.each do |waste|  
new\_waste = waste.clone  
new\_waste.event = @event  
new\_waste.save  
end

As for learning, everything I know is from [http://api.rubyonrails.com/](http://api.rubyonrails.com/)  
[http://www.rubycentral.com/ref/](http://www.rubycentral.com/ref/) and the Agile Web D. book.

---

<div class="post-metadata">

**Author:** ![sprsquish](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/d9b06d/32.png) [@sprsquish](https://www.ruby-forum.com/u/sprsquish)\
**Post date:** [April 23, 2006, 3:52am UTC](https://www.ruby-forum.com/t/anyone-know-how-to-copy-rows/58486/5 "2006-04-23T03:52:04Z")

</div>

Alex W. wrote:

> jeff stevens wrote:
> 
> > Hey all,
> > 
> > I’m trying to write something that allows one to copy several rows from  
> > a table and create new rows based on those rows. This will be used to  
> > intentionally duplicate rows. Did I mention that I was having little  
> > luck? I’m from a PHP world, but I’ve been getting really into Rails  
> > lately.
> > 
> > Here’s what I’ve got(assume an event has\_many wastes):
> > 
> > def wastePrepopulate  
> > @wastes = Waste.find\_all  
> > @wastes.each do |waste|  
> > Event.find(params[:id]).wastes.create(params[:waste])  
> > end  
> > flash[:notice] = ‘The records have been prepopulated.’  
> > redirect\_to :action =\> “showwastes”, :id =\>params[:id]  
> > end
> > 
> > If I feed parameters to it using a form, it will create new records with  
> > those parameters, but I can’t get it to use the data from  
> > @wastes=Waste.find\_all.
> > 
> > I’m ultimately trying to set up a way to create records based on  
> > existing data. Any help would be GREATLY appreciated.
> > 
> > Cheers,  
> > Monkey
> 
> Something like this should work
> 
> @event = Event.find(params[:id])  
> @wastes = Waste.find\_all  
> @wastes.each do |waste|  
> data = waste.attributes.reject do |key, value|  
> key == :id ||  
> key == :event\_id  
> end  
> @event.wastes.create(data)  
> end
> 
> First, you don’t to do “Event.find(params[:id])” in a loop since the  
> result will be the same every time, so sense adding that DB strain.
> 
> Second, active record objects have an “attributes” method that dumps  
> their data to a hash. We take that hash and reject the keys we don’t  
> want duplicated, in this case the id, since the new rows should have new  
> ids, and event\_id, since we want the new wastes to be associated with  
> the event we are calling create on.

He shoots…he scores!  
You are a gentleman and a scholar! It worked perfectly.

As for “Event.find(params[:id])” being part of the loop; that was just  
an embarrassing oversight. Your point is clear and well taken.

As for your approach; I wasn’t sure if rails would overwrite the ids  
automatically or not. Rejecting attributes makes perfect sense.

Where can I find some good reference. I’ve gone through some tutorials  
and bought the Agile Rails book, but that isn’t cutting it. Any ideas?  
Is there an up to date Active directory reference? For instance:

data = waste.attributes.reject do |key, value|  
key == :id ||  
key == :event\_id  
end

It’s simple, clean and straight forward, but I can’t find any place to  
find that kind of usage. I would not have come up with “reject”, but I  
should be able to. What did you read to get to where you are? I’m  
usually a spounge, but I need some water to soak up. 😉

Thanks a bunch for your previous reply, it was just what the doctor  
ordered!

Cheers,  
Monkey