Getting Started

Install:

dotnet add package Cocoar.Capabilities

All types are in the Cocoar.Capabilities namespace.

Quick Start: Compose and Query

A subject is any object you compose capabilities onto — it's the key that identifies a composition in the registry. Subjects can be strings, class instances, enum values, or any other object.

using Cocoar.Capabilities;

// 1. Create a scope
var scope = new CapabilityScope();

// 2. Compose capabilities onto a subject (here, the string "user-service")
scope.Compose("user-service")
    .Add(new LoggingCapability { Level = LogLevel.Debug })
    .Add(new RetryCapability { MaxAttempts = 3 })
    .Build();

// 3. Query the composition
var composition = scope.Compositions.GetRequired<string>("user-service");

var logging = composition.GetFirstOrDefault<LoggingCapability>();
Console.WriteLine(logging?.Level); // Debug

var all = composition.GetAll<RetryCapability>();
Console.WriteLine(composition.Has<LoggingCapability>()); // True

Quick Start: Primary Capability

public record ServiceIdentity(string Name, string Version) : IPrimaryCapability;

scope.Compose("user-service")
    .WithPrimary(new ServiceIdentity("UserService", "2.1.0"))
    .Add(new LoggingCapability { Level = LogLevel.Debug })
    .Build();

var composition = scope.Compositions.GetRequired<string>("user-service");
var identity = composition.GetRequiredPrimaryAs<ServiceIdentity>();
Console.WriteLine(identity.Name); // UserService

Quick Start: Multiple Contracts

public class EmailNotifier : INotifier, IHealthCheck
{
    public string Name => "Email";
    public bool IsHealthy => true;
}

scope.Compose("notifications")
    .AddAs<(INotifier, IHealthCheck)>(new EmailNotifier()) // tuple = register under both interfaces
    .Build();

var composition = scope.Compositions.GetRequired<string>("notifications");
var notifiers = composition.GetAll<INotifier>();      // [EmailNotifier]
var checks = composition.GetAll<IHealthCheck>();       // [EmailNotifier]

Key Types

Type	Role
CapabilityScope	Container that manages composers and compositions
Composer	Fluent builder for attaching capabilities to a subject
IComposition	Immutable, thread-safe result of a composition
IPrimaryCapability	Marker interface for the "identity" capability
CapabilityScopeOptions	Configuration for scope behavior

Next Steps

• Why Capabilities? — The problem this solves
• CapabilityScope — Deep dive into scopes
• Composer — Full builder API
• Composition — Query API reference
• Examples — Real-world patterns