01 Introduction

This module introduces OrigoDB, explaining what it is, how it works, when and when not to use it. The exercises are fairly simple and introduce some of the main concepts which will be explored in depth later.

Reading material

• Slides PDF
• OrigoDB Intro
• OrigoDB Quick start guide

Exercise 1

In this exercise you will play with an existing custom twitter model using scriptcs. If you don't have scriptcs, you can create a visual studio console application. The source for this model can be found here

1. Start a command prompt and navigate to the modules Ex01 folder

2. Install the OrigoDB from nuget by typing scriptcs -install origodb.core

3. Start the scriptcs REPL by typing scriptcs and enter the following statements:

   #r Twitter.Core.dll
   using OrigoDB.Core;
   using Twitter.Core;
   var t = new TwitterVerse();
   t.AddUser("unclebob");
   t.AddUser("robtheslob");
   t.Follow("robtheslob", "unclebob")
   t.Tweet("unclebob", "If you don't do TDD ur doing it wrong", DateTime.Now)
   t.Unfollow("unclebob", "robtheslob")

   You have created and manipulated a data model instance in memory but there is no engine controlling concurrency or providing persistence. You will fix this in the next step. Press CTRL+C to exit scriptcs, the current twitterverse will be lost forever.

4. Install origodb.core from nuget

5. Create a text file called twitter.csx with the following content:

   #r Twitter.Core.dll
   
   using OrigoDB.Core;
   using Twitter.Core;
   
   var db = Db.For<TwitterVerse>(); //transparent proxy with backing file storage in current directory
   
   db.AddUser("robtheslob");
   db.AddUser("neo");
   db.Follow("neo", "robtheslob");
   db.Tweet("neo", "What is the Matrix?", DateTime.Now);

6. Start the script and enter interactive REPL mode using scriptcs twitter.csx -REPL

7. Exit with CTRL+C when you've finished playing around

Takeways

• A snapshot and journal was created on disk
• If you execute Db.For<TwitterVerse>() again, the in-memory model will be restored from disk
• You used the transparent proxy feature
• Scriptcs is awesome

Exercise 2

In this excercise you will create a custom data model using object oriented domain modeling.

1. Create an empty NET 4.0 Class Library Project using Visual Studio named Todo.Core in Ex02\Starter

2. Create an entity class called Todo representing a single todo item.

   [Serializable]
   public class Todo
   {
       public DateTime? Due { get; private set; }
       public DateTime? Completed { get; private set; }
       public string Title { get; private set; }
       public readonly int Id;
   
       public Todo(int id, string title = "Untitled")
       {
           Id = id;
           Title = title;
       }
   }

3. Add a nuget reference to OrigoDB.Core

4. Create an anemic root data model class deriving from OrigoDB.Core.Model

   [Serializable]
   public class TodoModel : Model
   {
       public SortedDictionary<int, Todo> Todos { get; private set; }
       int _nextId = 1;
   
       public int GetNextId()
       {
           return _nextId++;
       }
       
       public TodoModel()
       {
           Todos = new SortedDictionary<int, Todo>();
       }
   }    

5. Create the following commands:

   [Serializable]
   public class AddTodoCommand : Command<TodoModel, int>
   {
       public readonly string Title;
   
       public AddTodoCommand(string title)
       {
           Title = title;
       }
   
       public override int Execute(TodoModel model)
       {
           int id = model.GetNextId();
           model.Todos[id] = new Todo(id, Title);
           return id;
       }
   }
   
   [Serializable]
   public class SetCompletedCommand : Command<TodoModel>
   {
       public readonly int Id;
       public readonly DateTime Completed;
   
       public SetCompletedCommand(int id, DateTime completed)
       {
           Id = id;
           Completed = completed;
       }
   
       public override void Execute(TodoModel model)
       {
           if (!model.Todos.ContainsKey(Id)) Abort("No such todo");
           model.Todos[Id].SetCompleted(Completed);
       }
   }

6. Add a SetCompleted method to the Todo class and make sure everything builds

   Now it's time to test drive the model, let's use scriptcs again.

7. Create a text file named todo.csx in the Ex02 directory with the following contents:

   #r Todo.Core/bin/debug/Todo.Core.dll
   
   using Todo.Core;
   using OrigoDB.Core;
   
   var engine = Engine.LoadOrCreate<TodoModel>();
   var command = new AddTodoCommand("Learn Scala");
   int id = engine.Execute(command);
   
   var todo = engine.Execute(db => db.Todos.Values.Where(t => t.Id == id).Single());
   
   engine.Execute(new SetCompletedCommand(id, DateTime.Now));
   
   var todo2 = engine.Execute(db => db.Todos[id]);

8. Start the script and remain in REPL mode.

9. Examine existing variables, play around, ask questions and discuss

Review

• You have created a class library with an entity, a root data model and commands.
• You have created an engine and executed commands and ad-hoc queries
• Note the snapshot and journal
• Scriptcs is awesome