Delete only the FOLLOWING tasks.

app/controllers/periodic_task_groups_controller.rb

@@ -1,8 +0,0 @@
-class PeriodicTaskGroupsController < ApplicationController
-  def destroy
-    @task_group = PeriodicTaskGroup.find(params[:id])
-    @task_group.destroy
-
-    redirect_to tasks_url, notice: I18n.t('periodic_task_groups.destroy.notice')
-  end
-end

app/controllers/tasks_controller.rb

@@ -56,7 +56,12 @@ class TasksController < ApplicationController
     task = Task.find(params[:id])
     # Save user_ids to update apple statistics after destroy
     user_ids = task.user_ids
-    task.destroy
+    if params[:periodic]
+      task.periodic_task_group.exclude_tasks_before(task)
+      task.periodic_task_group.destroy
+    else
+      task.destroy
+    end
     task.update_ordergroup_stats(user_ids)
 
     redirect_to tasks_url, :notice => I18n.t('tasks.destroy.notice')

app/helpers/periodic_task_groups_helper.rb

@@ -1,2 +0,0 @@
-module PeriodicTaskGroupsHelper
-end

app/models/periodic_task_group.rb

@@ -1,23 +1,29 @@
 class PeriodicTaskGroup < ActiveRecord::Base
-  has_many :tasks, :dependent => :destroy
+  has_many :tasks, dependent: :destroy
 
   PeriodDays = 7
   
   def has_next_task?
-    return false if self.tasks.empty?
-    return false if self.tasks.first.due_date.nil?
+    return false if tasks.empty?
+    return false if tasks.first.due_date.nil?
     return true
   end
 
   def create_next_task
-    template_task = self.tasks.first
+    template_task = tasks.first
     self.next_task_date ||= template_task.due_date + PeriodDays
     
     next_task = template_task.dup
-    next_task.due_date = self.next_task_date    
+    next_task.due_date = next_task_date    
     next_task.save
 
     self.next_task_date += PeriodDays
     self.save
   end
+
+  def exclude_tasks_before(task)
+    tasks.where("due_date < '#{task.due_date}'").each do |t|
+      t.update_attribute(:periodic_task_group, nil)
+    end
+  end
 end

app/views/tasks/show.haml

@@ -30,5 +30,5 @@
   = link_to t('ui.delete'), task_path(@task), :method => :delete, :confirm => "Die Aufgabe wirklich löschen?",
     class: 'btn btn-danger'
   - if @task.periodic?
-    = link_to t('ui.delete_all'), periodic_task_group_path(@task.periodic_task_group), :method => :delete, 
-      :confirm => "Alle Aufgaben dieser wöchentlichen Aufgabe wirklich löschen?", class: 'btn btn-danger'
+    = link_to 'Aufgabe und folgende löschen', task_path(@task, periodic: true), method: :delete, 
+      confirm: "Diese und alle folgenden wöchentlichen Aufgaben wirklich löschen?", class: 'btn btn-danger'

config/routes.rb

@@ -70,8 +70,6 @@ Foodsoft::Application.routes.draw do
       end
     end
 
-    resources :periodic_task_groups, only: [:destroy]
-
     resources :messages, :only => [:index, :show, :new, :create]
 
     namespace :foodcoop do