Custom Header

# Custom header versioning
@app.route('/api/users')
def get_users():
    version = request.headers.get('X-API-Version', '1')

    if version == '1':
        data = [{"id": u.id, "name": u.name} for u in users]
    elif version == '2':
        data = [{"id": u.id, "name": u.name, "email": u.email} for u in users]
    else:
        return jsonify({"error": "Unsupported version"}), 400

    response = jsonify(data)
    response.headers['X-API-Version'] = version
    return response

# Version header as a decorator
def versioned(min_version='1', max_version='2'):
    def decorator(f):
        @wraps(f)
        def wrapper(*args, **kwargs):
            version = request.headers.get('X-API-Version', '1')
            if version < min_version or version > max_version:
                return jsonify({"error": "Version not supported"}), 400
            kwargs['api_version'] = version
            return f(*args, **kwargs)
        return wrapper
    return decorator

@app.route('/api/products')
@versioned(min_version='1', max_version='2')
def get_products(api_version):
    if api_version == '1':
        return jsonify([p.basic() for p in products])
    return jsonify([p.detail() for p in products])

// Express custom header versioning
app.get('/api/users', (req, res) => {
  const version = req.headers['x-api-version'] || '1';

  res.set('X-API-Version', version);

  switch(version) {
    case '1':
      return res.json(users.map(u => ({ id: u.id, name: u.name })));
    case '2':
      return res.json(users.map(u => ({ id: u.id, name: u.name, email: u.email })));
    default:
      return res.status(400).json({ error: 'Unsupported version' });
  }
});

// Middleware pattern
function versionMiddleware(req, res, next) {
  req.apiVersion = req.headers['x-api-version'] || '1';
  res.set('X-API-Version', req.apiVersion);
  next();
}

app.use('/api', versionMiddleware);