Variable class attribute access?

Rails
1

I have an array of similar objects which I need to sort based on one
their
many attributes.
For instance, Campaign has clicks, impressions and cost. I want to be
able
to dynamically sort by any of those attributes.

def sort_campaign_by(attr)
@campaigns.sort_by{ |c| c.#{attr} }
end

this (obviously) doesn’t work but hopefully my intentions are clear.
I’m
trying not to use a case statement - seems unnecessarily lengthy and
brittle.
note, I can’t sort them in the AR call, it needs to happen afterwards.

Anyone know how to do this?

thanks,
ed

2

Ed Hickey wrote:

I have an array of similar objects which I need to sort based on one
their
many attributes.
For instance, Campaign has clicks, impressions and cost. I want to be
able
to dynamically sort by any of those attributes.

def sort_campaign_by(attr)
@campaigns.sort_by{ |c| c.#{attr} }
end

this (obviously) doesn’t work but hopefully my intentions are clear.
I’m
trying not to use a case statement - seems unnecessarily lengthy and
brittle.
note, I can’t sort them in the AR call, it needs to happen afterwards.

Anyone know how to do this?

thanks,
ed

Try Array#sort or Array#sort!
http://www.ruby-doc.org/core/classes/Array.html#M000397

def sort_campaign_by(attr)
@campaigns.sort! { |a, b| a[attr] <=> b[attr] }
end

With active record objects, all the db stored attributes are accessible
as if the object was a hash. So “@user[:name]” is the same as
“@user.name”. This makes it easier to dynamically call attributes.

You can also do it directly in the SQL you use to fetch your campaigns.

def index
@campaigns = Campaign.find(:all, :order => params[:sort_attr])
end

This option would probably be a bit faster. Let the database do what
it’s good at. However, if you need to use the data before it’s been
sorted this would not be an option for you.