owl_mediator 1.0.2

An implementation of the architectural mediator pattern, with CQRS support.

example/README.md

Mediator

The Mediator class acts as the main entry point for this package, it doesn't have any complex dependencies, and in order to use it you just have to create an instance of it:

Mediator mediator = Mediator();

You probably only want a single instance of the mediator in your application.

Commands and command handlers

In order to execute commands through the Mediator you have to:

1. Create your command:

   // Required only when you're creating a command / command handler.
   import 'package:owl_mediator/command.dart';
   
   // Create a new command, must implement ICommand<ResultType> only once.
   // The command only needs fields if your handler will require them.
   class ConvertToStringCommand implements ICommand<String> {
     final int number;
   
     ConvertToStringCommand(this.number);
   }
   

2. Then your command handler:

   // Required only when you're creating a command / command handler.
   import 'package:owl_mediator/command.dart';
   
   // Create a new handler for your command, each command should get one, and only one handler.
   // Multiple return types might be supported in the future.
   class ConvertToStringCommandHandler
       implements ICommandHandler<ConvertToStringCommand, String> {
     @override
     Future<String> handle(ConvertToStringCommand request) {
       // Put your handler implementation here.
       // Handlers are async by default to allow for future middleware support.
       String result = request.number.toString();
       return Future.value(result);
     }
   }
   

   Optionally you can also create an extension method that uses your command handler in order to make it easier to run the command:

   // Required to add an extension method on the mediator.
   import 'package:owl_mediator/mediator.dart';
   
   // OPTIONAL:
   //	I recommend creating an extension method for your queries to make them
   //	a tiny bit nicer to run. This will hopefully be code-generated later on.
   extension ConvertToStringCommandMediator on Mediator {
     Future<String> convertToString(int number) {
       return runCommand(ConvertToStringCommand(number));
     }
   }
   

3. Register the command handler on your mediator:

   // Required when you want to use/initialise the mediator.
   import 'package:owl_mediator/mediator.dart';
   
   void main() {
     // Create a new mediator, this should only be needed once per your application.
     Mediator mediator = Mediator();
   
     // Register the command handler for its command type.
     // This will hopefully be code-generated later on.
     mediator.registerCommand(ConvertToStringCommandHandler());
   }
   

4. Execute the command:

   // Create and run your command.
   String result1 = await mediator.runCommand(ConvertToStringCommand(123));
   print(result1);
   
   // If you implemented the optional extension method, then you can do this instead.
   String result2 = await mediator.convertToString(123);
   print(result2);
   

Queries and query handlers

In order to execute queries through the Mediator you have to:

1. Create your query:

   // Required only when you're creating a query / query handler.
   import 'package:owl_mediator/query.dart';
   
   // Create a new query, must implement IQuery<ResultType> only once.
   // The query only needs fields if your handler will require them.
   class GetAsStringQuery implements IQuery<String> {
     final int number;
   
     GetAsStringQuery(this.number);
   }
   

2. Then your query handler:

   // Required only when you're creating a query / query handler.
   import 'package:owl_mediator/query.dart';
   
   // Create a new handler for your query, each query should get one, and only one handler.
   // Multiple return types might be supported in the future.
   class GetAsStringQueryHandler
       implements IQueryHandler<GetAsStringQuery, String> {
     @override
     Future<String> handle(GetAsStringQuery request) {
       // Put your handler implementation here.
       // Handlers are async by default to allow for future middleware support.
       String result = request.number.toString();
       return Future.value(result);
     }
   }
   

   Optionally you can also create an extension method that uses your query handler in order to make it easier to run the query:

   // Required to add an extension method on the mediator.
   import 'package:owl_mediator/mediator.dart';
   
   // OPTIONAL:
   //	I recommend creating an extension method for your queries to make them
   //	a tiny bit nicer to run. This will hopefully be code-generated later on.
   extension GetAsStringQueryMediator on Mediator {
     Future<String> getAsString(int number) {
       return runQuery(GetAsStringQuery(number));
     }
   }
   

3. Register the query handler on your mediator:

   // Required when you want to use/initialise the mediator.
   import 'package:owl_mediator/mediator.dart';
   
   void main() {
     // Create a new mediator, this should only be needed once per your application.
     Mediator mediator = Mediator();
   
     // Register the query handler for its query type.
     // This will hopefully be code-generated later on.
     mediator.registerQuery(GetAsStringQueryHandler());
   }
   

4. Execute the query:

   // Create and run your query.
   String result1 = await mediator.runQuery(GetAsStringQuery(123));
   print(result1);
   
   // If you implemented the optional extension method, then you can do this instead.
   String result2 = await mediator.getAsString(123);
   print(result2);