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John Merlino

2011-Apr-19 20:59 UTC

do a select from another table within a model

Hey all,

This right here:

  scope :index_blog, {
    :select => "blog_posts.*",
    :joins => "INNER JOIN categories ON category.id
blog_posts.category_id",
    :conditions =>"blog_posts.enabled = 1"
  }

returns this:

Mysql2::Error: Not unique table/alias: ''categories'': SELECT
blog_posts.*
FROM `categories` INNER JOIN categories ON category.id blog_posts.category_id
WHERE (blog_posts.enabled = 1)

But I am not trying to select blog_posts.* from categories. I am trying
to select blog_posts.* from blog_posts. However, because I do this
within the category model, it fills in categories. And I don''t know how
to select from blog posts from category model. I''m also curious if
there
is a better way to do this?

Thanks for response.

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Colin Law

2011-Apr-19 21:06 UTC

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Re: do a select from another table within a model

On 19 April 2011 21:59, John Merlino
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:> Hey all,
>
> This right here:
>
>  scope :index_blog, {
>    :select => "blog_posts.*",
>    :joins => "INNER JOIN categories ON category.id >
blog_posts.category_id",
>    :conditions =>"blog_posts.enabled = 1"
>  }
>
> returns this:
>
> Mysql2::Error: Not unique table/alias: ''categories'':
SELECT blog_posts.*
> FROM `categories` INNER JOIN categories ON category.id >
blog_posts.category_id WHERE (blog_posts.enabled = 1)
>
> But I am not trying to select blog_posts.* from categories. I am trying
> to select blog_posts.* from blog_posts. However, because I do this
> within the category model, it fills in categories. And I don''t
know how
> to select from blog posts from category model. I''m also curious if
there
> is a better way to do this?
Unless I misunderstand something can''t you just say
category.blog_posts with :conditions specified for enabled = 1?

Colin

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Frederick Cheung

2011-Apr-19 21:11 UTC

head link

Re: do a select from another table within a model

On Apr 19, 9:59 pm, John Merlino
<li...-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:> Hey all,
>
> This right here:
>
>   scope :index_blog, {
>     :select => "blog_posts.*",
>     :joins => "INNER JOIN categories ON category.id >
blog_posts.category_id",
>     :conditions =>"blog_posts.enabled = 1"
>   }
>
> returns this:
>
> Mysql2::Error: Not unique table/alias: ''categories'':
SELECT blog_posts.*
> FROM `categories` INNER JOIN categories ON category.id >
blog_posts.category_id WHERE (blog_posts.enabled = 1)
>
> But I am not trying to select blog_posts.* from categories. I am trying
> to select blog_posts.* from blog_posts. However, because I do this
> within the category model, it fills in categories. And I don''t
know how
> to select from blog posts from category model. I''m also curious if
there
> is a better way to do this?
>
Why are you trying to define a scope on blog posts in the categories
model? Even if you fix the query, rails will still try and create
instances of Category rather than instances of BlogPost

Fred> Thanks for response.
>
> --
> Posted viahttp://www.ruby-forum.com/.
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Kendall Gifford

2011-Apr-19 21:12 UTC

head link

Re: do a select from another table within a model

On Tuesday, April 19, 2011 2:59:57 PM UTC-6, Ruby-Forum.com User
wrote:>
> Hey all,
>
> This right here:
>
>   scope :index_blog, {
>     :select => "blog_posts.*",
>     :joins => "INNER JOIN categories ON category.id >
blog_posts.category_id",
>     :conditions =>"blog_posts.enabled = 1"
>   }
>First of all, "this right here" is in what model/file? I''m
gonna guess from
your error it is in your Category model in category.rb? 
> returns this:
>
> Mysql2::Error: Not unique table/alias: ''categories'':
SELECT blog_posts.*
> FROM `categories` INNER JOIN categories ON category.id >
blog_posts.category_id WHERE (blog_posts.enabled = 1)
> 
Another side problem: "ON category.id..." is your table named
categories or
category?
 
> But I am not trying to select blog_posts.* from categories. I am trying
> to select blog_posts.* from blog_posts. However, because I do this
> within the category model, it fills in categories.
>Ahh, so we are in the Category model. This explains why the "FROM 
categories" part exists. Even though you''re looking for
blog_posts, don''t
worry about this.

Try:

  scope :index_blog, {
    :select => "blog_posts.*",
    :joins => "INNER JOIN blog_posts ON categories.id = 
blog_posts.category_id",
    :conditions =>"blog_posts.enabled = 1"
  }
> I''m also curious if there
> is a better way to do this?
>That depends on what you''re trying to do.

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John Merlino

2011-Apr-19 21:55 UTC

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Re: do a select from another table within a model

Actually, all i wanted to do initially was this:

def filter_scoper(scoper)
    logger.info "The current class is #{self.class}" 
#CategoriesController

    if params.has_key? :filter
      send :"#{params[:filter]}_filter_scoper", scoper
    elsif self.class.respond_to?(:blog_filter_scoper)
      send :"blog_filter_scoper"
    else
      scoper #call index_scoper
    end
  end

Basically if the controller responds to blog_filter_scoper, then I want 
to pass blog_filter_scoper as the model:

  def blog_filter_scoper
    BlogPost
  end

However, for some reason despite the fact that self.class outputs 
CategoriesController and when I load the categories page, it does not 
respond to the blog_filter_scoper method even though I defined 
blog_filter_scoper method within the categories controller.

I don''t know why this is happening.

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John Merlino

2011-Apr-19 22:16 UTC

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Re: do a select from another table within a model

ok I must never forget that in haml it works like this:

- @resources.each do |r|
  %h1= r.title
  %p= r.body


not this:

= @resources.each do |r|
  %h1- r.title
  %p- r.body

Otherwise, you will get an ActiveRecord array as an object.

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Kendall Gifford

2011-Apr-19 22:38 UTC

head link

Re: do a select from another table within a model

On Tuesday, April 19, 2011 3:55:52 PM UTC-6, Ruby-Forum.com User
wrote:>
> Actually, all i wanted to do initially was this:
>
> def filter_scoper(scoper)
>     logger.info "The current class is #{self.class}" 
> #CategoriesController
>
>     if params.has_key? :filter
>       send :"#{params[:filter]}_filter_scoper", scoper
>     elsif self.class.respond_to?(:blog_filter_scoper)
>Do you mean: elsif self.respond_to?(:blog_filter_scoper)
Note the lack of ".class" after self.
 
>       send :"blog_filter_scoper"
>     else
>       scoper #call index_scoper
>     end
>   end
>
> Basically if the controller responds to blog_filter_scoper, then I want 
> to pass blog_filter_scoper as the model:
>
>   def blog_filter_scoper
>     BlogPost
>   end
>Yeah, looks like you''re wanting to call an instance method as I pointed
out
above.
 
> However, for some reason despite the fact that self.class outputs 
> CategoriesController and when I load the categories page, it does not 
> respond to the blog_filter_scoper method even though I defined 
> blog_filter_scoper method within the categories controller.
>
I don''t know why this is happening.>
It would appear to me that your immediate problem is the line of code I 
pointed out above.

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John Merlino

2011-Apr-19 23:12 UTC

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Re: do a select from another table within a model

> It would appear to me that your immediate problem is the line of code I
> pointed out above.

Yeah I got it now. Basically:

if self.class.respond_to?

will only respond to class methods of the class, not instance methods 
and since attr_accessor returns instance methods, that if will return 
false. So basically what I had to do was:

    elsif self.class.method_defined? :blog_filter_scoper

And that worked above. And then within my categories controller:

  def blog_filter_scoper
    BlogPost.for_posts 1
  end


That will call the blogpost named scope and pass the argument 1 so now 
depending on which controller is invoked, we can pass different 
arguments to for_posts to determine which posts to display.

The only thing I don''t like now about this is that I am passing an 
integer 1. I''d rather do something like Category[:news].id - where
rails
will search the categories table with news value and then pull the id of 
that value which could be 1. I think that''s better than hardcoding 1 
right there. I guess that''s the next thing I need to figure out.

Thanks for all responses.

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Frederick Cheung

2011-Apr-20 07:26 UTC

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Re: Re: do a select from another table within a model

On 20 Apr 2011, at 00:12, John Merlino
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org> wrote:
>> It would appear to me that your immediate problem is the line of code I
>> pointed out above.
> 
> 
> Yeah I got it now. Basically:
> 
> if self.class.respond_to?
> 
> will only respond to class methods of the class, not instance methods 
> and since attr_accessor returns instance methods, that if will return 
> false. So basically what I had to do was:
> It''s simpler than that. blah.respond_to?(:foo) returns true if ruby
believes you can do blah.foo, so in particular self.class.respond_to?(:blah)
checks (in your case) whether CategoriesController.blah can be called whereas
self.respond_to?(:blah) checks whether self.blah would work.

method_defined? is a slightly more circuitous route to this and won''t
always work in a world like rails where methods are often created on the fly
from method_missing

Fred

>    elsif self.class.method_defined? :blog_filter_scoper
> 
> And that worked above. And then within my categories controller:
> 
>  def blog_filter_scoper
>    BlogPost.for_posts 1
>  end
> 
> 
> That will call the blogpost named scope and pass the argument 1 so now 
> depending on which controller is invoked, we can pass different 
> arguments to for_posts to determine which posts to display.
> 
> The only thing I don''t like now about this is that I am passing an
> integer 1. I''d rather do something like Category[:news].id - where
rails
> will search the categories table with news value and then pull the id of 
> that value which could be 1. I think that''s better than hardcoding
1
> right there. I guess that''s the next thing I need to figure out.
> 
> Thanks for all responses.
> 
> -- 
> Posted via http://www.ruby-forum.com/.
> 
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