# Spot the error (I can't, I'm new)

**URL:** <https://www.ruby-forum.com/t/spot-the-error-i-cant-im-new/57798>\
**Category:** Rails\
**Created:** [April 14, 2006, 8:22am UTC](https://www.ruby-forum.com/t/spot-the-error-i-cant-im-new/57798 "2006-04-14T08:22:16Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![B\_Gates](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/ea5d25/32.png) [@B\_Gates](https://www.ruby-forum.com/u/B_Gates)\
**Post date:** [April 14, 2006, 8:22am UTC](https://www.ruby-forum.com/t/spot-the-error-i-cant-im-new/57798/1 "2006-04-14T08:22:16Z")

</div>

I have a form that I want to use to update multiple  
objects. In the controller,  
@grades = Grade.find(params[:grade].keys)  
@grades.each\_with\_index do |grade, i|  
grade.update\_attribute(params[:grade][i])  
end  
all\_valid = @grades.inject(true) {|memo, c|  
c.valid? && memo }  
this doesn’t update the attributes as I would expect.  
(I would just use  
Grade.update(params[:grade].keys,params[:grade].values)  
but I can’t figure out how to validate the data using  
that method. Could someone please explain what I’m  
doing wrong here?

Thanks,  
Brian Gates

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---

<div class="post-metadata">

**Author:** ![B\_Gates](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/ea5d25/32.png) [@B\_Gates](https://www.ruby-forum.com/u/B_Gates)\
**Post date:** [April 14, 2006, 2:53pm UTC](https://www.ruby-forum.com/t/spot-the-error-i-cant-im-new/57798/2 "2006-04-14T14:53:35Z")

</div>

For one thing, remember that update\_attribute is for updating a single  
attribute. It looks like you’re updating multiple attributes per grade  
in your each loop, so you probably want to use update\_attributes  
instead, no?

B Gates wrote:

> I have a form that I want to use to update multiple  
> objects. In the controller,  
> @grades = Grade.find(params[:grade].keys)  
> @grades.each\_with\_index do |grade, i|  
> grade.update\_attribute(params[:grade][i])  
> end  
> all\_valid = @grades.inject(true) {|memo, c|  
> c.valid? && memo }  
> this doesn’t update the attributes as I would expect.  
> (I would just use  
> Grade.update(params[:grade].keys,params[:grade].values)  
> but I can’t figure out how to validate the data using  
> that method. Could someone please explain what I’m  
> doing wrong here?
> 
> Thanks,  
> Brian Gates
> 
> * * *
> 
> Do You Yahoo!?  
> Tired of spam? Yahoo! Mail has the best spam protection around  
> [http://mail.yahoo.com](http://mail.yahoo.com)

---

<div class="post-metadata">

**Author:** ![B\_Gates](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/ea5d25/32.png) [@B\_Gates](https://www.ruby-forum.com/u/B_Gates)\
**Post date:** [April 14, 2006, 6:07pm UTC](https://www.ruby-forum.com/t/spot-the-error-i-cant-im-new/57798/3 "2006-04-14T18:07:27Z")

</div>

update attribute takes 2 parameters: the name of the attribute and its  
new value, you are only giving it the value, and it doesnt know what  
field you are talking about.

Try:  
grade.update\_attribute(:letter\_grade, params[:grade][i])

Or with a bit of refactoring:  
@grades = []  
params[:grade].each\_pair do |key, value|  
grade = Grade.find(key)  
grade.update\_attribute(:letter\_grade, value)  
@grades \<\< grade  
end  
all\_valid = @grades.inject(true) do |memo, c|  
c.valid? && memo  
}

This wau you don;t have to use “params[:grade][i]” which is standard  
practice in other languages, but in ruby it’s usually quite unnesesary.

-Alex

B Gates wrote:

> I have a form that I want to use to update multiple  
> objects. In the controller,  
> @grades = Grade.find(params[:grade].keys)  
> @grades.each\_with\_index do |grade, i|  
> grade.update\_attribute(params[:grade][i])  
> end  
> all\_valid = @grades.inject(true) {|memo, c|  
> c.valid? && memo }  
> this doesn’t update the attributes as I would expect.  
> (I would just use  
> Grade.update(params[:grade].keys,params[:grade].values)  
> but I can’t figure out how to validate the data using  
> that method. Could someone please explain what I’m  
> doing wrong here?
> 
> Thanks,  
> Brian Gates
> 
> * * *
> 
> Do You Yahoo!?  
> Tired of spam? Yahoo! Mail has the best spam protection around  
> [http://mail.yahoo.com](http://mail.yahoo.com)