Class Maybe

napi.h:269–306

/// caught yet. In that case, a "Nothing" value is returned.
template <class T>
class Maybe {
 public:
  bool IsNothing() const;
  bool IsJust() const;

  /// Short-hand for Unwrap(), which doesn't return a value. Could be used
  /// where the actual value of the Maybe is not needed like Object::Set.
  /// If this Maybe is nothing (empty), node-addon-api will crash the
  /// process.
  void Check() const;

  /// Return the value of type T contained in the Maybe. If this Maybe is
  /// nothing (empty), node-addon-api will crash the process.
  T Unwrap() const;

  /// Return the value of type T contained in the Maybe, or using a default
  /// value if this Maybe is nothing (empty).
  T UnwrapOr(const T& default_value) const;

  /// Converts this Maybe to a value of type T in the out. If this Maybe is
  /// nothing (empty), `false` is returned and `out` is left untouched.
  bool UnwrapTo(T* out) const;

  bool operator==(const Maybe& other) const;
  bool operator!=(const Maybe& other) const;

 private:
  Maybe();
  explicit Maybe(const T& t);

  bool _has_value;
  T _value;

  template <class U>
  friend Maybe<U> Nothing();
  template <class U>
  friend Maybe<U> Just(const U& u);
};

template <class T>
inline Maybe<T> Nothing();