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Classes

A class is the largest of the three structural types. A STRUCT holds only data and a PROTOCOL holds only requirements.

A class holds both properties and methods and it can sit in an inheritance hierarchy.

CLASS Circle:
    PUBLIC center: Point
    PUBLIC radius: Float
    PUBLIC area(): Float

The members follow the same visibility rules as every structural type and its methods may carry functional intents like standalone functions.

Inheritance with EXTENDS​

A class may extend one parent class with EXTENDS, inheriting its members:

CLASS Employee EXTENDS Person:
    PUBLIC salary(): Integer

Employee gains everything Person declares and adds its own salary(). Classes use single inheritance: exactly one EXTENDS target, written as a single contextual name.

Conformance with IMPLEMENTS​

A class may declare that it satisfies one or more protocols with IMPLEMENTS, listing them comma-separated:

CLASS Employee EXTENDS Person IMPLEMENTS Serializable, Comparable:
    PUBLIC name: String
    PUBLIC salary(): Integer

EXTENDS and IMPLEMENTS can appear together, in that order. A class implements any number of protocols while extending at most one class. This appears often in real designs:

CLASS FileStrategy IMPLEMENTS StrategyProtocol:
CLASS SettingStrategy IMPLEMENTS StrategyProtocol:
CLASS ManifestStrategy IMPLEMENTS StrategyProtocol:

Three classes share one contract. A class body can be empty when the declaration itself, meaning which protocols it fulfils, is the point.

Overriding with OVERRIDE​

When a class redeclares a method it inherited from its parent, it must mark the redeclaration with OVERRIDE:

CLASS Controller/AbstractIntertiaController EXTENDS Neos/ActionController:
    PROTECTED renderContext: Domain/Render/Context

    OVERRIDE PUBLIC renderView()

The OVERRIDE keyword comes before the visibility. It is needed because the parent class be defined EXTERN.

Putting it together​

A realistic class draws on the whole design section: composite types, methods, inheritance and conformance.

STRUCT Domain/Render/Context:
    PUBLIC component: String
    PUBLIC props: Array[Unknown]

CLASS Domain/Render/Fusion:
    PUBLIC prepareView(Neos/FusionView, Domain/Render/Context)

CLASS Domain/AssetVersion/StrategyFactory:
    PUBLIC buildFromConfiguration(String | Array[String]): ?StrategyProtocol