VerticalSlices: Skill for Claude Code

Create a strongly-typed Concept that wraps a primitive domain value.

Never use raw primitives in domain models

Replace Guid, string, int, etc. with a ConceptAs<T> record whenever the value has domain meaning.

Pick the base: value vs identity

• Value concept (name, amount, code) → derive from ConceptAs<T>.
• Identity concept (an entity's event-source id) → derive from EventSourceId<T>. Never use ConceptAs<Guid> for an event-source id — EventSourceId<T> already supplies the conversions to/from T, to/from EventSourceId, and to string, so Chronicle resolves the key automatically.

Value concept template

// Copyright (c) Cratis. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.

using Cratis.Concepts;

namespace <NamespaceRoot>.<Feature>;

/// <summary>
/// Represents the <description>.
/// </summary>
/// <param name="Value">The underlying <type> value.</param>
public record <ConceptName>(<UnderlyingType> Value) : ConceptAs<<UnderlyingType>>(Value)
{
    /// <summary>
    /// Represents an unset <ConceptName>.
    /// </summary>
    public static readonly <ConceptName> NotSet = new(<emptyValue>);

    /// <summary>
    /// Implicitly converts a <UnderlyingType> to a <ConceptName>.
    /// </summary>
    public static implicit operator <ConceptName>(<UnderlyingType> value) => new(value);
}

Identity concept template (event-source id)

using Cratis.Chronicle.Events;

namespace <NamespaceRoot>.<Feature>;

/// <summary>
/// Represents the identity of a <description>.
/// </summary>
/// <param name="Value">The underlying <type> value.</param>
public record <ConceptName>(<UnderlyingType> Value) : EventSourceId<<UnderlyingType>>(Value)
{
    public static readonly <ConceptName> NotSet = new(<emptyValue>);
    public static <ConceptName> New() => new(Guid.NewGuid());   // when backed by Guid
    public static implicit operator <ConceptName>(<UnderlyingType> value) => new(value);
}