Question

Unfortunately this mess works: Do you have suggestings for cleaning up this code: I’m trying to use a activerecord to compare two table columns, “needed” and “amount” then update a boolean column, depending on the returned data. Totally breaking do-not-repeat coding.

def update
    @inventory = Inventory.find(params[:id])

    respond_to do |format|
      if @inventory.update_attributes(params[:inventory])
            unless @inventory.needed.nil?
                if @inventory.needed < @inventory.amount then
                @inventory.instock = true
                @inventory.update_attributes(params[:inventory])
                else
                @inventory.instock = false
                @inventory.update_attributes(params[:inventory])
                end
            end
        flash[:notice] = 'Inventory was successfully updated.'
        format.html { redirect_to(@inventory) }
        format.xml  { head :ok }
      else
        format.html { render :action => "edit" }
        format.xml  { render :xml => @inventory.errors, :status => :unprocessable_entity }
      end
    end
  end

Cheers!

Answer 1

First, keep the extraneous logic out of your controller:

def update
  @inventory = Inventory.find(params[:id])

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

Then, handle the instock attribute with a callback on the Inventory model. Something like:

before_update :check_instock, :unless => Proc.new { |inventory| inventory.needed.nil? } 

def check_instock
  if needed < amount
    instock = true
  else
    instock = false
  end
end