Mixins

Mixins provide field reuse for .cstack models. They are a schema authoring convenience, not a runtime inheritance feature.

Syntax

Declare a top-level mixin block and apply it inside a model with @use(...).

mixin AuditFields {
  createdAt DateTime @default(dbgenerated())
  updatedAt DateTime @default(dbgenerated())
}

model Post {
  @use(AuditFields)

  id Int @id
  title String
}

You can apply more than one mixin:

mixin AuditFields {
  createdAt DateTime @default(dbgenerated())
  updatedAt DateTime @default(dbgenerated())
}

mixin SoftDelete {
  deletedAt DateTime?
}

model Post {
  @use(AuditFields, SoftDelete)

  id Int @id
  title String
}

Semantics

CrateStack expands mixin fields into the model before semantic validation and before Rust, Dart, and TypeScript code generation. That means:

generated clients and generated server code see normal model fields after expansion
validator rules run on the expanded model field set
mixins do not create a separate generated runtime type

Rules

Current mixin support is intentionally narrow:

mixins are only supported as top-level declarations
@use(...) is only supported inside model blocks
mixins contain fields, not model-level attributes
mixins must not declare @id
model-local fields win on name conflicts with mixin fields

Example of local override:

mixin Timestamps {
  createdAt DateTime
}

model Post {
  @use(Timestamps)

  id Int @id
  createdAt DateTime?
}

In that example, the model’s createdAt DateTime? definition wins.

Non-goals

Mixins are not:

polymorphism
inheritance between generated model types
a way to share model @@... attributes
a way to declare shared primary keys

Studio Eject Field Attributes

Overview

Get Started

Guides

Banking Readiness

Architecture

Tooling

Studio

Reference

Internals

Mixins

Mixins

Syntax

Semantics

Rules

Non-goals

​Mixins

​Syntax

​Semantics

​Rules

​Non-goals

Mixins

Syntax

Semantics

Rules

Non-goals