# :include?

**URL:** <https://www.ruby-forum.com/t/include/130281>\
**Category:** Rails\
**Created:** [February 27, 2008, 2:13am UTC](https://www.ruby-forum.com/t/include/130281 "2008-02-27T02:13:49Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![confundido](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/90ced4/32.png) [@confundido](https://www.ruby-forum.com/u/confundido)\
**Post date:** [February 27, 2008, 2:13am UTC](https://www.ruby-forum.com/t/include/130281/1 "2008-02-27T02:13:49Z")

</div>

I’d like some adviceif possile

i have 2 models Location and Listing Location has many Listings Listing  
belongs to location. Using teh acts\_as\_geocodable plugin i have  
geocoded the Location model.

this allows me to do a find like so

location = Location.find(:all, :origin =\> postal\_code, :order =\>  
“distance asc”)

i would like to include the child objects in the result so i can show  
listings sorted by distance.

i posted at [railsforum.com](http://railsforum.com) and Duplex suggested using :include as  
follows :-

location = Location.find :all, :origin =\> postal\_code,  
:order =\> “distance asc”,  
:include =\> :listings #eager-loading for  
performance  
:conditions =\> “state = ‘published’”

i get mysql error when i try that pasted here to save space  
[http://pastie.caboo.se/157933](http://pastie.caboo.se/157933)

This is my first project so I’m not sure but i think maybe its unable to  
do the :include because distance is a generated field or maybe it’s  
because using :origin already is a type of JOIN query. any ideas? I’m  
thinking maybe the way round this is to find a way to do the sql query  
directly and bypass rails?

any suggestions welcome  
cheers  
Rigagoogoo

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**Author:** ![confundido](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/90ced4/32.png) [@confundido](https://www.ruby-forum.com/u/confundido)\
**Post date:** [February 27, 2008, 2:34am UTC](https://www.ruby-forum.com/t/include/130281/2 "2008-02-27T02:34:04Z")

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Hi Nathan,

The generated SQL does not contain a “distance” field yet you are  
trying to order based on that field (:order =\> “distance asc”). Does  
your Location model have this field? If not, then I would suggest you  
remove the :order option and then try again. I don’t understand why  
this didn’t fail in your first example without the :include option  
though ☹

Regards,  
Jabbslad

On Feb 27, 1:13 am, Nathan S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)

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**Author:** ![confundido](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/90ced4/32.png) [@confundido](https://www.ruby-forum.com/u/confundido)\
**Post date:** [February 27, 2008, 4:48am UTC](https://www.ruby-forum.com/t/include/130281/3 "2008-02-27T04:48:18Z")

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Hi Jabbslad

thanks for such a quick response 🙂

Location model doesn’t have distance field, it should be generated  
by the inclusion of :origin in the find method indeed if i do the  
following

location = Location.find :all, :origin =\> “some\_postcode”, :order =\>  
“distance asc”

it works fine and translates into an SQL query that gets mysql to  
determine the distance between the Locations longitude and latitude  
and the long/lat of the provided postcode - heres the SQL it creates  
[http://pastie.caboo.se/157973](http://pastie.caboo.se/157973)

it fails when i try to combine it with :include. so given :include  
doesn’t play ball with extended find acts\_as\_geocodable provides how  
do i get to the endpoint i need

given Location has many Listings display Listings in order of  
distance from users postcode my options as i see it are:-

1. Iterate through the results and create a new array but that hits  
the database for each location.

location= Location.find :all, :origin =\> “some\_postcode”, :order =\>  
“distance asc”

1. maybe better to use  
locations= Location.find :all, :origin =\> “some\_postcode”, :order =\>  
“distance asc”  
listings = Listing.find :all  
and some ruby to combine them into one array?

2. Use the locations result to build a new sql query?

3. fix the problem with :origin and include - probably not beginner  
territory 😉

frankly I don’t know how to do any of the above so all of those  
options are daunting 🙂 so any advice or examples would be great.

cheers  
Rigagoogoo

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**Author:** ![confundido](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/90ced4/32.png) [@confundido](https://www.ruby-forum.com/u/confundido)\
**Post date:** [February 27, 2008, 6:31am UTC](https://www.ruby-forum.com/t/include/130281/4 "2008-02-27T06:31:24Z")

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On 27 Feb 2008, at 03:47, nathan sharkey wrote:

> “distance asc”
> 
> it works fine and translates into an SQL query that gets mysql to  
> determine the distance between the Locations longitude and latitude  
> and the long/lat of the provided postcode - heres the SQL it creates  
> [Parked at Loopia](http://pastie.caboo.se/157973)

I imagine that origin’s magic uses the :select option to include that  
extra computed column. Unfortunately eager loading overwrites  
that :select with its own and so that’s not going o play ball.  
Personally I’d go with a varian on 2:

locations= Location.find :all, :origin =\> “some\_postcode”, :order =\>  
“distance asc”  
all\_listings = Listing.find :all, :conditions =\> [‘location\_id in  
(?)’, locations] #pre rails 2 i think that needs to be changed to  
locations.map(&:id)

listings\_hash = all\_listings.inject({}) do |memo, listing|  
listings\_for\_location = (memo[listing.location\_id] ||= [])  
listings\_for\_location \<\< listing  
memo  
end

listings\_hash is now a hash with all your listings, so if you want to  
know all the listings for location[2], then you just do  
locations[listings[2].id]

or cut out the middle man and do

location\_map = {}  
locations.each do |location|  
location.listings.loaded  
location\_map[location.id] = location  
end

all\_listings.each do |listing|  
parent = location\_map[listing.location\_id]  
association\_proxy = parent.listings  
association\_proxy.loaded  
association\_proxy.target.push(listing)  
end

which sets up the association magic so that you can just do  
location.listings

Fred

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**Author:** ![confundido](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/90ced4/32.png) [@confundido](https://www.ruby-forum.com/u/confundido)\
**Post date:** [February 27, 2008, 1:55pm UTC](https://www.ruby-forum.com/t/include/130281/5 "2008-02-27T13:55:52Z")

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Hi fred thanks for the examples they’ve opened my eyes to the .include  
() method after some playing with your exaple by using p to print out  
the variables as i ent in console I think I understand it and will  
probably be able to cobble together what i need using it but the  
second example throws me with .loaded i’ve googled it but come up  
with nothing? i’ve searched a rails project using textmate and not  
found it as a method and searched the ruby docs. can you advise what  
it does?

cheers  
Nathan

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<div class="post-metadata">

**Author:** ![confundido](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/90ced4/32.png) [@confundido](https://www.ruby-forum.com/u/confundido)\
**Post date:** [February 27, 2008, 2:07pm UTC](https://www.ruby-forum.com/t/include/130281/6 "2008-02-27T14:07:41Z")

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On 27 Feb 2008, at 12:54, nathan sharkey wrote:

> Hi fred thanks for the examples they’ve opened my eyes to the .include  
> () method after some playing with your exaple by using p to print out  
> the variables as i ent in console I think I understand it and will  
> probably be able to cobble together what i need using it but the  
> second example throws me with .loaded i’ve googled it but come up  
> with nothing? i’ve searched a rails project using textmate and not  
> found it as a method and searched the ruby docs. can you advise what  
> it does?

The key bit of information here is that location.listings isn’t an  
array (even though it looks like one). It’s an association proxy.  
That’s why you can do things like location.listings.find and so on.  
When you try and do something to the association proxy that requires  
the actual elements (eg if you try to access location.listings.first)  
then the listings are actually loaded. What we’re doing here is  
prefetching all the listings and stuffing them into where the  
association proxy stores the actual array (target). The call to loaded  
means that the proxy will think that it has already loaded the array.  
This sort of stuff isn’t really documented much, but you can work it  
out for yourself by reading the relevant bits of the rails source  
(associations.rb, association\_proxy.rb etc…)

Fred

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**Author:** ![confundido](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/90ced4/32.png) [@confundido](https://www.ruby-forum.com/u/confundido)\
**Post date:** [February 27, 2008, 4:29pm UTC](https://www.ruby-forum.com/t/include/130281/7 "2008-02-27T16:29:20Z")

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Thanks Fred for the explanation i think i understand the intention  
just not the how yet. i have only just learn’t the meaning of  
include and inject methods. 🙂

i think i am spending too much time worrying about calls to my sql  
there is no point spending days trying to understand this for my  
first app. It could be years before i got enough traffic to it for  
it to really make a difference. All I want is to create a view with  
all Listings ordered by reletive distance from users postcode. The  
method can be tuned at a later date if it ever needs to be I’ve  
already spent 2 days trying to understand…

so what’s easiest (not necessarily best) way for me to do this?

using acts\_as\_geocodable I can get relative distance to postcode in  
the three following ways

locations = Locations.find(:all, :origin =\> postcode, :order =\>  
“distance”)  
locations[0].distance

location = Location.find(0, :origin =\> postcode)  
location.distance

\*\*\*\*\*\*the above .distance method is only available for the result set  
not for the model in general also it can’t be combined with an  
include \*\*\*\*\*\*\*

Listing.find(1).location.distance\_to postcode

ignoring how many sql queries are required how do i create a view  
that works?

so something like :-

listings = Listing.find\_all\_by\_state(“published”) # returns all my  
published listings  
for each listing in listings do  
puts listing.name &" “& listing.intro &” “&  
listing.location.distance\_to(“postcode”) &” "& "link to"listing.url  
end

but ordered by distance and usable in a view not just the console???

thanks again  
Nathan