Class Diagrams

A class diagram is a set of named class boxes, each holding member rows, plus the directed relations between them.

Overview

The model lives in Atelier\Diagram\ClassDiagram\: ClassDiagram (the class boxes and relations), ClassBox (id plus its member rows), ClassMember (a single text row), and ClassRelation (from, to, optional label). All model classes are immutable.

Reach for it to show the shape of a type model: the classes in a domain, the fields and operations on each, and how they reference one another. Use an ER diagram instead when you are modeling database entities and their keyed relationships rather than code-level types.

Format

Class diagrams round-trip through a classDiagram subset:

classDiagram
    class User
    User : +id int
    class Order
    User --> Order
    User --> Order : places

Class ids match [A-Za-z_][A-Za-z0-9_]*. Classes referenced by members or relations are auto-declared in first-use order. Inheritance arrows, class blocks, annotations, namespaces, generics, structured method parsing, and styling are rejected, never skipped. Full grammar: Mermaid support.

Builder API

ClassDiagramBuilder (or Diagram::classDiagram(), which returns it) is the one way to build the model:

use Atelier\Diagram\Diagram;

$diagram = Diagram::classDiagram()
    ->class('User')                             // declare a class
    ->member('User', '+id int')                 // add a member row
    ->member('User', '+email string')
    ->member('Order', '+total Money')           // auto-declares Order
    ->relation('User', 'Order', 'places')       // labeled directed relation
    ->build();

Diagram::of($diagram)->saveSvg('classes.svg');

class()

Declares a class. Repeating an id is a no-op; an empty id throws.

Argument	Type	Description
$id	string	Class identifier.

member()

Appends a member row and auto-declares the class if unseen. Declaration order is the layout tie-breaker.

Argument	Type	Description
$classId	string	Owning class identifier.
$text	string	Member row text.

relation()

Adds a directed relation and auto-declares unknown endpoints.

Argument	Type	Description
$from	string	Source class identifier.
$to	string	Target class identifier.
$label	?string	Optional relation label.

build()

Assembles the immutable ClassDiagram in declaration order.

Options

• Determinism: layout is source-order based and deterministic; the same model always yields the same SVG.

Layout\ClassDiagram\ClassDiagramLayoutEngine places class boxes in a source-order grid and routes relations with atelier/layout orthogonal ports. Class names and member rows are bounded and wrapped, so long labels do not force unusable boxes. Relation labels are centered on the route, wrapped when needed, and drawn over a background halo so the edge stays readable.

Themes

Class diagrams use nodeFillColor and nodeStrokeColor for the boxes and their row separators, nodeStrokeColor for relation edges and arrowheads, and textColor for class names and member rows.

All presets apply (Theme::default(), dark(), blueprint(), mono(), neutral()), and a Scene\BackgroundPattern (as in blueprint()) sits behind the boxes. See Theming.

Pass Theme::blueprint() to toSvg() for a deep navy canvas with thin cyan strokes.

Parse

Header keyword: classDiagram.

$diagram = Diagram::fromMermaid($source);        // throws ParseException
$result  = Diagram::tryFromMermaid($source);      // non-throwing ParseResult

toMermaid() / toMarkdown() serialize a built model back. Full grammar and round-trip rules: Mermaid support.

Debug

On a rejected source, inspect ParseResult::getDiagnostic() (a ParserDiagnostic with a message, a stable code, and a source span) or catch ParseException (getLineNumber(), getSourceLine()). Render a code frame with ParserDiagnosticFormatter:

$result = Diagram::tryFromMermaid($source);
if ($result->isFailure()) {
    echo \Atelier\Diagram\Parser\Support\ParserDiagnosticFormatter::format($result->getDiagnostic());
}

See parser diagnostics.