Only applying attribute_update to attributes that have actually changed

[Xavius]

Background: I'm trying to add an edit function to user data on a website. I have it currently setup so a user can click edit and the user is taken to a new page with text fields already populated with their existing information. They can then make changes and click update.

What I wanted to do is figure out which text fields have different text, from what they were originally populated with, and only update those fields (only update attributes that are different from before). Then keeping track of what fields have been updated alert the user (for instance: "changes have been made to: first name, last name)"

def edit_manage
  @user_info = User.find_by_id(session[:user_id])
  updated = []
  if request.post?
    @update = User.find_by_id(session[:user_id])
    @update.update_attributes(params)
    #collect original values to compare later
    t = {:first_name => @update.first_name, :middle_name => @update.middle_name,
    :last_name => @update.last_name, :email => @update.email, :about => @update.about}
    params.each do |key,value|
      if t[key] != value #is the original value different from the new?
        @update.update_attribute(key,value)
        updated << key.to_s
      end
    end
 
    changed = ''
    updated.each_with_index do |value,index|
      changed << ', ' unless index.zero?
      changed << value
    end
    flash[:notice] = "#{changed} updated"
    redirect_to :action => 'manage'
  end
end

Needless to say this doesn't work and I'm guessing there is a much easier way to do this.

===
got it to work by doing the following:

def edit_manage 
    @user_info = User.find_by_id(session[:user_id])
 
    if request.post?
      @update = User.find_by_id(session[:user_id])
      t = {:first_name => @update.first_name, :middle_name => @update.middle_name,
      :last_name => @update.last_name, :email => @update.email, :about => @update.about}
      updated = []
      t.each do |key,value|
        if value != params[key]
          @update.update_attribute(key,params[key])
          updated << key.to_s
        end
      end
 
      changed = ''
      updated.each_with_index do |value,index|
        changed << ', ' unless index.zero?
        changed << value
      end
 
      flash[:notice] = "Updated: #{changed}"
      redirect_to :action => 'manage'
    end
  end

However, I'm still looking for a more efficient way of doing that!

[AllTom]

Note: #update_attribute bypasses validations!

Edge Rails has #changed_attributes, and lots of stuff related to this is on its way: http://ryandaigle.com/articles/2008/...-dirty-objects. I would back-port that stuff so that when it's finally released, you don't have to change your code. Its syntax is pretty nice anyway.

[Xavius]

In what type of situation(s) would validations come in handy?

Cool changes, thanks for the heads-up!

[AllTom]

In terms of your text fields that are likely varchar:

- The database will happily truncate data you send to it, so long inputs will be silently chopped. A validation that checks length will catch this.
- Validations are an easy way to check for goofball inputs like empty strings.

In practice, I end up adding one or more validations on every field. Require non-blank text fields, require a username of minimum length, require a password of minimum length, require an e-mail of valid format, require text that's valid XML, require a referenced row that satisfies a certain condition, etc.

Get all sorts of crazy ideas at: http://api.rubyonrails.org/classes/A...ssMethods.html