messageChains.ts

// As a direct chain of calls
class FlightBooking {
  private plane: Plane;

  constructor(plane: Plane) {
    this.plane = plane;
  }

  // ...
  isSeatAvailable(rowNumber: number, seat: string): boolean {
    return this.plane.getRows()[rowNumber - 1].isAvailable(seat);
  }
}

// Chaining calls through intermediate results 
class FlightBooking {
  private plane: Plane;

  constructor(plane: Plane) {
    this.plane = plane;
  }

  // ...
  isSeatAvailable(rowNumber: number, seat: string): boolean {
    let rows = this.plane.getRows();
    const row = rows[rowNumber - 1];
    return row.isAvailable(seat);
  }
}

//----------------------------------------------------------------------------
//----------------------------------------------------------------------------

class FlightBooking {
  private plane: Plane;

  constructor(plane: Plane) {
    this.plane = plane;
  }

  // ...
  isSeatAvailable(rowNumber: number, seat: string): boolean {
    return this.plane.hasAvailableSeatAt(rowNumber, seat);
  }
}

class Plane {
  private rows: Rows;

  constructor(rows: Rows) {
    this.rows = rows;
  }

  // ...
  hasAvailableSeatAt(rowNumber: number, seat: string): boolean {
    return this.rows.isAvailable(rowNumber, seat);
  }
}

class Rows {
  private readonly rows: Row[];

  constructor(rows: Row[]) {
    this.rows = rows;
  }

  // ...
  isAvailable(rowNumber: number, seat: string): boolean {
    const row = this.rows[rowNumber - 1];
    return row.isAvailable(seat);
  }
}