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Permission group hierarchy

Nest roles and permission groups so aggregate permissions can be evaluated recursively.

Problem

An access-control system must evaluate permissions across individual roles and nested groups while allowing authorization logic to process both leaves and containers through the same interface.

Related patterns

Composite

View pattern →

Implementations

Composite

TypeScriptApplication

Composite in TypeScript

Represents files and folders through one interface so callers can calculate the size of an individual file or an entire directory tree uniformly.

TypeScript
interface FileSystemNode {
  getName(): string;
  getSizeInBytes(): number;
}

class FileNode implements FileSystemNode {
  constructor(
    private readonly name: string,
    private readonly sizeInBytes: number,
  ) {}

  getName() {
    return this.name;
  }

  getSizeInBytes() {
    return this.sizeInBytes;
  }
}

class FolderNode implements FileSystemNode {
  private readonly children: FileSystemNode[] = [];

  constructor(private readonly name: string) {}

  getName() {
    return this.name;
  }

  add(child: FileSystemNode) {
    this.children.push(child);
  }

  getSizeInBytes() {
    return this.children.reduce(
      (total, child) => total + child.getSizeInBytes(),
      0,
    );
  }
}

const invoices = new FolderNode("invoices");
invoices.add(new FileNode("january.pdf", 120_000));
invoices.add(new FileNode("february.pdf", 140_000));

const archive = new FolderNode("archive");
archive.add(invoices);
archive.add(new FileNode("readme.txt", 2_000));

console.log(archive.getSizeInBytes());

Associated technologies