RoR: How to modify the controller to accept update several params only?

Question

Here is the code generated by rails:

def update
  @user = User.find(params[:id])

  respond_to do |format|
    if @user.update_attributes(params[:user])
      flash[:notice] = 'User was successfully updated.'
      format.html { redirect_to(@user) }
      format.xml  { head :ok }
    else
      format.html { render :action => "edit" }
      format.xml  { render :xml => @user.errors, :status => :unprocessable_entity }
    end
  end
end      

But I don't want user to update the whole user, assume that my user have fname, lname and gender, instead of remove the gender from the view, I want to restrict that the update method ONLY accept fname and lname only, if he/she want to update the gender, I won't allow him/her to do so. How can I restrict the user to do so? thank you.

Answer 1

Use Hash parameters of the update_attributes

@user = User.find(params[:id])
@user.update_attributes(:fname=>params[:user][:fname], :lname=>params[:user][:lname])

Answer 2

You can delete unwanted attributes from the param[:user] Hash:

# ...
attributes = params[:user]
gender = attributes.delete :gender
raise SomeError unless gender.blank?
if @user.update_attributes(attributes)
  # ...
end
# ...

This code removes :gender from the Hash and checks if it is filled in. If so, an exception is raised. Of course you could give a nice warning or silently ignore the fact that the gender was filled in.

Answer 3

or add a custom @user.update_only() method, which makes it also easier to reuse in different contexts...

class User
  def update_only(attrs = {}, *limit_to)
    update_attributes(attrs.delete_if { |k,v| !limit_to.include?(k.to_sym) })
  end
end

Then just do something along the lines of

@user.update_only(params[:user], :fname, :lname)

Answer 4

There are two methods in ActiveRecord that come in handy in cases like these, attr_protected and attr_accessible.

You use them like this:

class MyModel < ActiveRecord::Base
    attr_accessible :fname, :lname #Allow mass-assignment
    attr_protected :secret #Do not allow mass-assignment
end

model = MyModel.new(:fname => "Firstname", :lname => "Lastname", :secret => "haha")
puts model.fname # "Firstname"
puts model.lname # "Lastname"
puts model.secret = nil # Can not be set through mass-assignment
model.secret = "mysecret" # May only be assigned like this
puts model.secret # "mysecret"

However, if you only need this functionality at one place, then Salil's solution will work just as well.

One thing to note is that you should use attr_acessible to whitelist attributes that are OK to mass-assign, and make every other attribute protected. By doing so, you hinder mean people for updating data they are not supposed to touch.

See the docs for more info.