missed elements in array

rubyonrails-talk
1

Hi, i despair in case of an array. I'll take some data into an array, but when i iterate the array some elements of the array seems to be missed, but the missing element are displayed in the view. I'm using the Plugin Rails_Authorization.

my Code:

  def index     if !params[:task_id] #Tasks der 1. ebene anzeigen, auf die der User zugriff hat       @tasks = current_user.is_owner_of_what + current_user.is_moderator_of_what + current_user.is_user_of_what       @tasks.uniq! #doppelte Einträge auf einen reduzieren       puts @tasks       @tasks.each do |task|         puts task.id         if !task.root? #ist Task kein wurzelelement?           if (current_user.has_roles_for? Task.find(task.parent_id) ) #Hat der Benutzer Rechte auf Parent Task?              @tasks.delete(task) #Objekt aus Array schmeißen da nur die Elemente der 1. Ebene dargestellt werden sollen, auf die der Benutzer Rechte hat

          end         end       end     else #Wenn Subtasks angezeigt werden sollen       @task=Task.find(params[:task_id])       load_subtasks       @tasks=@subtasks     end     #@tasks = Task.all     respond_to do |format|

      format.html #index.html.erb       format.xml { render :xml => @tasks }     end   end

And My Debugging Log:

#<Task:0x1036e6ca8> #<Task:0x1036e3ee0> #<Task:0x1036df958> #<Task:0x1036dc190> #<Task:0x1036d8ea0> #<Task:0x1036d5138> #<Task:0x1036d18f8> #<Task:0x1036cbd90> 5 6 8 12 14

2

Hi, i despair in case of an array. I'll take some data into an array, but when i iterate the array some elements of the array seems to be missed, but the missing element are displayed in the view. I'm using the Plugin Rails_Authorization.

You're deleting from the array as you are iterating over it - don't do that.

Fred

3

Frederick Cheung wrote:

4

Yep. A common mistake when iterating arrays. One solution is to build a new array containing the objects you want, rather than deleting objects that you don't want. There may be better approaches that might use less memory though.

And if you do want to do that, a rubyish way of doing that is to use methods like select

The relevant portion of the code above could be written as

@tasks = @tasks.select {|task| task.root? || ! current_user.has_roles_for?(Task.find(task.parent_id))}

(probably a little faster too - Array#delete is O(n))

Fred