# Find\_by\_parent\_id

**URL:** <https://www.ruby-forum.com/t/find-by-parent-id/107300>\
**Category:** Rails\
**Created:** [June 20, 2007, 10:08am UTC](https://www.ruby-forum.com/t/find-by-parent-id/107300 "2007-06-20T10:08:45Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![huang\_zhimin](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/54ee81/32.png) [@huang\_zhimin](https://www.ruby-forum.com/u/huang_zhimin)\
**Post date:** [June 20, 2007, 10:08am UTC](https://www.ruby-forum.com/t/find-by-parent-id/107300/1 "2007-06-20T10:08:45Z")

</div>

I guess it will return all the objects whose parent\_id is assigned. But  
I  
get only an object.

I have to do like these

```
@parent_id = params[:parent_id]
if @parent_id.nil?
  conditions = ["parent_id is null"]
else
  conditions = ["parent_id = ?", @parent_id]
end
@categories = Category.find(:all, :conditions => conditions)

```

But I expected that can be done like this  
@categories = Category.find\_by\_parent\_id(params[:parent\_id]) #  
only  
one object

Does anybody have good idea?

–

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---

<div class="post-metadata">

**Author:** ![huang\_zhimin](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/54ee81/32.png) [@huang\_zhimin](https://www.ruby-forum.com/u/huang_zhimin)\
**Post date:** [June 20, 2007, 10:55am UTC](https://www.ruby-forum.com/t/find-by-parent-id/107300/2 "2007-06-20T10:55:53Z")

</div>

huang zhimin wrote:

> ```
> end
> @categories = Category.find(:all, :conditions => conditions)
> 
> ```
> 
> But I expected that can be done like this  
> @categories = Category.find\_by\_parent\_id(params[:parent\_id]) #  
> only one object
> 
> Does anybody have good idea?

Perhaps you’re looking for find\_all\_by\_parent\_id?

–  
Cheers,

- Jacob A.

---

<div class="post-metadata">

**Author:** ![huang\_zhimin](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/54ee81/32.png) [@huang\_zhimin](https://www.ruby-forum.com/u/huang_zhimin)\
**Post date:** [June 20, 2007, 12:26pm UTC](https://www.ruby-forum.com/t/find-by-parent-id/107300/3 "2007-06-20T12:26:07Z")

</div>

Thanks

On 6/20/07, Jacob A. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> > ```
> > conditions = ["parent_id is null"]
> > 
> > ```
> 
> Perhaps you’re looking for find\_all\_by\_parent\_id?
> 
> –  
> Cheers,
> 
> - Jacob A.
> 
> >

–

> **[CodeLineStatistics](https://sourceforge.net/projects/mycodeline/)**
>
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