# Default Data Templates

**URL:** <https://www.ruby-forum.com/t/default-data-templates/140023>\
**Category:** Rails\
**Created:** [June 10, 2008, 5:42am UTC](https://www.ruby-forum.com/t/default-data-templates/140023 "2008-06-10T05:42:36Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![glenviewjeff](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/a587f6/32.png) [@glenviewjeff](https://www.ruby-forum.com/u/glenviewjeff)\
**Post date:** [June 10, 2008, 5:42am UTC](https://www.ruby-forum.com/t/default-data-templates/140023/1 "2008-06-10T05:42:36Z")

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In my database, I have a lot of duplicated data between entries. For  
example, I might have a database of foods where Meats is the parent  
object and Cheeseburger is one of its children.

o=Food.New  
o.name = “Meats”  
o.text = “This food is really unhealthy…lots of text”  
o.category = “Meats”  
o.save

p=Food.New  
p.parent = o.id  
p.name = “Cheeseburger”  
p.save

If unpopulated, I’d like the parent’s data to be accessed. I  
implemented this inside the model on an attribute-by-attribute basis,  
but this seems to stink of bad design, since every time I add a new  
field, I have to write duplicate code that checks if the attribute is  
empty.

Any ideas would be greatly appreciated.

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**Author:** ![glenviewjeff](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/a587f6/32.png) [@glenviewjeff](https://www.ruby-forum.com/u/glenviewjeff)\
**Post date:** [June 10, 2008, 12:38pm UTC](https://www.ruby-forum.com/t/default-data-templates/140023/2 "2008-06-10T12:38:28Z")

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On 10 Jun 2008, at 04:41, glenviewjeff wrote:

> p=Food.New  
> p.parent = o.id  
> p.name = “Cheeseburger”  
> p.save

> If unpopulated, I’d like the parent’s data to be accessed. I  
> implemented this inside the model on an attribute-by-attribute basis,  
> but this seems to stink of bad design, since every time I add a new  
> field, I have to write duplicate code that checks if the attribute is  
> empty.

you could do something like

class \<\< self  
def attr\_parent \*names  
names.each do |name|  
define\_method name do  
self.read\_attribute(name) || parent.send(name)  
end  
end  
end  
end

then you can stick  
attr\_parent :name, :text, … in your model (try and pick a better  
name than me) and it will call the parent object if the attribute is  
nil (if you also want this to happen on a empty string just change the  
conditions. You could also stick this in a module and extend  
ActiveRecord::Base with it, and then all ActiveRecord subclasses will  
be able to use it

Fred

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<div class="post-metadata">

**Author:** ![glenviewjeff](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/a587f6/32.png) [@glenviewjeff](https://www.ruby-forum.com/u/glenviewjeff)\
**Post date:** [June 14, 2008, 9:38pm UTC](https://www.ruby-forum.com/t/default-data-templates/140023/3 "2008-06-14T21:38:23Z")

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Thank you very much Fred. It took me some time to learn Ruby’s OO  
implementation well enough to understand your post, but I was  
successful.

For anyone with similar problems, I’ve pasted my code below.  
Incidentally, my code smells bad again, in that I am explicitly  
testing for specific classes (i.e., string or not,) and I would think  
this would be better handled by extending the class for each data type  
(string, etc.) Any thoughts?

Thanks,  
Jeff

class FoodItem \< ActiveRecord::Base  
class \<\< self  
def attr\_parent \*names  
names.each do |name|  
define\_method name do  
self.read\_attribute( name )  
if self.read\_attribute( name ).is\_a? String  
if self.read\_attribute( name ).empty? && !  
self.DuplicateOf.nil?  
FoodItem.find(self.DuplicateOf).send(name)  
else  
self.read\_attribute( name )  
end  
else  
self.read\_attribute(name) ||  
FoodItem.find(self.DuplicateOf).send(name)  
end  
end  
end  
end  
end

```
attr_parent :FoodType, :FoodPrice

```

end

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<div class="post-metadata">

**Author:** ![glenviewjeff](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/a587f6/32.png) [@glenviewjeff](https://www.ruby-forum.com/u/glenviewjeff)\
**Post date:** [June 14, 2008, 9:57pm UTC](https://www.ruby-forum.com/t/default-data-templates/140023/4 "2008-06-14T21:57:58Z")

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On 14 Jun 2008, at 20:37, glenviewjeff wrote:

> 

I’m not entirely sure what you’re doing there, but it sounds like you  
could simplify it to

if self.read\_attribute( name ).blank?  
FoodItem.find(self.DuplicateOf).send(name)  
else  
self.read\_attribute( name )  
end  
(blank? returns true for nil, an empty string, an empty array etc…

You might also want to use an association (so that the find is cached  
rather than hitting the database each time. It’s also ruby convention  
that method names be underscored, not camelcased (which is used for  
constants, eg class names), as it is it makes your code look very odd.

Fred