KCGroups

optionalgadget.h
1 // SPDX-FileCopyrightText: 2020 Henri Chain <[email protected]>
2 // SPDX-FileCopyrightText: 2020 Kevin Ottens <[email protected]>
3 //
4 // SPDX-License-Identifier: LGPL-2.1-or-later
5 
6 #ifndef OPTIONALGADGET_H
7 #define OPTIONALGADGET_H
8 
9 #ifdef STD_OPTIONAL_AVAILABLE
10 #include <optional>
11 #endif
12 
13 #ifdef __cpp_lib_optional
14 namespace KCGroups
15 {
16 template<typename T>
17 using optional = std::optional<T>;
18 }
19 #else
20 #include "optional.h"
21 #endif
22 
23 #define OPTIONAL_GADGET(T, name) \
24  /** \
25  @brief An optional T. \
26  The parameterless constructor creates a name without value. \n \
27  Use name(const T &val) to create a name with a value. \n \
28  Can be implicitly converted to T (undefined behavior when no value) and to bool (same has hasValue()) \
29  */ \
30  class KCGROUPS_EXPORT name : public KCGroups::optional<T> \
31  { \
32  Q_GADGET \
33  \
34  /** \
35  @brief The underlying T value. Returns a default T if hasValue() is false. \n \
36  Has a reset() method to remove the value, which can be reached in QML via x.value = undefined \
37  @accessors getValue(), setValue(), reset() \
38  */ \
39  Q_PROPERTY(T value READ getValue WRITE setValue RESET reset) \
40  \
41  /** \
42  @brief Whether there is currently a value defined \
43  @accessors hasValue() \
44  */ \
45  Q_PROPERTY(bool hasValue READ hasValue) \
46  \
47  public: \
48  /** \
49  The underlying value type. Equal to T \
50  */ \
51  using value_type = T; \
52  \
53  using KCGroups::optional<T>::optional; \
54  \
55  /** \
56  @brief get value or default \
57  @return underlying value if hasValue() is true, else default T value \
58  */ \
59  T getValue() \
60  { \
61  return *this ? **this : T(); \
62  } \
63  \
64  /** \
65  @brief set a T value \
66  @param val: the value to set \
67  */ \
68  void setValue(const T &val) \
69  { \
70  *reinterpret_cast<KCGroups::optional<T> *>(this) = val; \
71  } \
72  \
73  /** \
74  @brief whether a value is currently set \
75  @return true if a value is present, false otherwise \
76  */ \
77  bool hasValue() \
78  { \
79  return static_cast<bool>(*this); \
80  } \
81  }; \
82  \
83  inline bool operator==(const name &lhs, const name &rhs) \
84  { \
85  return static_cast<KCGroups::optional<typename name::value_type>>(lhs) == \
86  static_cast<KCGroups::optional<typename name::value_type>>(rhs); \
87  } \
88  \
89  inline bool operator!=(const name &lhs, const name &rhs) \
90  { \
91  return static_cast<KCGroups::optional<typename name::value_type>>(lhs) != \
92  static_cast<KCGroups::optional<typename name::value_type>>(rhs); \
93  } \
94  \
95  template<typename U> \
96  bool operator==(const name &lhs, const KCGroups::optional<U> &rhs) \
97  { \
98  return static_cast<KCGroups::optional<typename name::value_type>>(lhs) == rhs; \
99  } \
100  \
101  template<typename U> \
102  bool operator!=(const name &lhs, const KCGroups::optional<U> &rhs) \
103  { \
104  return static_cast<KCGroups::optional<typename name::value_type>>(lhs) != rhs; \
105  } \
106  \
107  template<typename T> \
108  bool operator==(const KCGroups::optional<T> &lhs, const name &rhs) \
109  { \
110  return lhs == static_cast<KCGroups::optional<typename name::value_type>>(rhs); \
111  } \
112  \
113  template<typename T> \
114  bool operator!=(const KCGroups::optional<T> &lhs, const name &rhs) \
115  { \
116  return lhs != static_cast<KCGroups::optional<typename name::value_type>>(rhs); \
117  } \
118  \
119  Q_DECLARE_METATYPE(name) \
120  static_assert(true, "")
121 
122 #endif // OPTIONALGADGET_H
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