# Trying to use find my model but I get an error

**URL:** <https://www.ruby-forum.com/t/trying-to-use-find-my-model-but-i-get-an-error/141466>\
**Category:** Rails\
**Created:** [June 26, 2008, 4:37am UTC](https://www.ruby-forum.com/t/trying-to-use-find-my-model-but-i-get-an-error/141466 "2008-06-26T04:37:02Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![DavidPaquet](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/a587f6/32.png) [@DavidPaquet](https://www.ruby-forum.com/u/DavidPaquet)\
**Post date:** [June 26, 2008, 4:37am UTC](https://www.ruby-forum.com/t/trying-to-use-find-my-model-but-i-get-an-error/141466/1 "2008-06-26T04:37:02Z")

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Hello everyone,

I’m pretty sure that my problem is easy but I’ve been fiddling with  
this for an hour and I cannot see why it’s not working

So in my model I defined this method :

def self.previous  
find(:first, :conditions =\> [“time  
\< ?”,self.time,self.stop\_id], :order =\> “time DESC”)  
end

So I tried my code in the console

and when I do p.previous I get : NoMethodError: undefined method  
`find’ for #Passage:0x2100b24

(p is valid instance of Passage)

Do anyone have an idea ?

Thanks!

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**Author:** ![DavidPaquet](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/a587f6/32.png) [@DavidPaquet](https://www.ruby-forum.com/u/DavidPaquet)\
**Post date:** [June 26, 2008, 5:31am UTC](https://www.ruby-forum.com/t/trying-to-use-find-my-model-but-i-get-an-error/141466/2 "2008-06-26T05:31:58Z")

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On Jun 25, 2008, at 7:36 PM, DavidPaquet wrote:

> \< ?",self.time,self.stop\_id], :order =\> “time DESC”)

You’ve declared the method ‘previous’ to be a _class_ method (via the  
“self.”). But then you call it on an _instance_ of that class.

Change the method to this:

def previous  
class.find(…)  
end

Also, youre conditions specify two arguments, but only one ‘?’ to  
substitute in a value. And you’ll want to remove the “self.” from  
those arguments as well.

-philip

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<div class="post-metadata">

**Author:** ![DavidPaquet](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/a587f6/32.png) [@DavidPaquet](https://www.ruby-forum.com/u/DavidPaquet)\
**Post date:** [June 26, 2008, 6:53am UTC](https://www.ruby-forum.com/t/trying-to-use-find-my-model-but-i-get-an-error/141466/3 "2008-06-26T06:53:17Z")

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Yeah sorry my fault I posted an old version and didnt look.

What I did is that I created a module called PassageFinder instead

module PassageFinder

def previous  
find(:first, :conditions =\> [“time \< ?”,Time.now], :order =\> “time  
DESC”)  
end

def next  
find(:first, :conditions =\> [“time \> ?”,Time.now], :order =\> “time  
ASC”)  
end

end

and I extended my relation with it so now I can do  
parent.passages.next and it’s work 🙂

Thanks tho!

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<div class="post-metadata">

**Author:** ![DavidPaquet](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/a587f6/32.png) [@DavidPaquet](https://www.ruby-forum.com/u/DavidPaquet)\
**Post date:** [June 26, 2008, 11:33pm UTC](https://www.ruby-forum.com/t/trying-to-use-find-my-model-but-i-get-an-error/141466/4 "2008-06-26T23:33:22Z")

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Well yes, I started from an example which I didn’t really understand  
at first and I tried to “fix it”.

You are right that I what I wanted was an instance method but I don’t  
remember why it was not working yesterday. But after a some digging,  
I found that named scope are exactly what I was looking for. They  
also take in consideration my associations

So my final solution is :

named\_scope :previous, lambda { |limit| { :conditions =\> [‘time  
\< ?",Time.now’], :limit =\> limit } }

So now I can do bus\_stop.previous.3 and I get the previous 3 passages.

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<div class="post-metadata">

**Author:** ![DavidPaquet](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/a587f6/32.png) [@DavidPaquet](https://www.ruby-forum.com/u/DavidPaquet)\
**Post date:** [June 26, 2008, 9:35am UTC](https://www.ruby-forum.com/t/trying-to-use-find-my-model-but-i-get-an-error/141466/5 "2008-06-26T09:35:57Z")

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Hi David,

Looks like you’ve defined a class method, but are trying to call it from  
an instance of that class. You’d need to call it like: Passage.previous.  
Also, if time and stop\_id are unique per instance, you’ll run into  
problems there as well. Not sure what you’re trying to accomplish, but  
it looks as though you could just make it an instance method (ie: remove  
the “self” from def self.previous).

Hope that helps.

Matt