Qt--宏

宏的知识

#define <宏名> (<参数表>) <宏体>#undef <宏名>#ifdef <宏名>    ...#else    ...#endif//define中的三个特殊符号：#，##，#@#define STRCAT(x,y) x##y //连接x和y成一个字符串#define TOCHAR(x) #@x  //给x加上单引号#define TOSTR(x) #x //给x加上双引号

宏是C/C++系列语言的一大特色，它将一个标识符定义为一个字符串，在预处理阶段源程序中的该标识符均以指定的字符串来代替，使用宏可以使代码更加简洁和增强可读性。

Qt中的宏

操作系统宏、处理器相关宏、编译器宏

#define Q_OS_X // 例如 Q_OS_WIN#deinfe Q_PROCESSOR_X // 例如 Q_PROCESSOR_X86_32#define Q_BYTE_ORDER Q_LITTLE_ENDIAN // 字节序：小端模式#define Q_PROCESSOR_WORDSIZE   4 #define Q_CC_X // 例如 Q_CC_MINGW

动态库宏

#ifdef Q_OS_WIN    #define Q_DECL_EXPORT     __declspec(dllexport)    #define Q_DECL_IMPORT     __declspec(dllimport)#endif

命名空间宏

#define QT_USE_NAMESPACE using namespace ::QT_NAMESPACE;#define QT_BEGIN_NAMESPACE namespace QT_NAMESPACE {#define QT_END_NAMESPACE }

Qt注释宏（注释类、函数、访问限制符）

#define QT_ANNOTATE_CLASS(type, ...)#define QT_ANNOTATE_FUNCTION(x)#define QT_ANNOTATE_ACCESS_SPECIFIER(x)

Qt信号与槽机制相关宏

#define slots Q_SLOTS#define signals Q_SIGNALS#define emit#define Q_SLOTS QT_ANNOTATE_ACCESS_SPECIFIER(qt_slot)#define Q_SIGNALS public QT_ANNOTATE_ACCESS_SPECIFIER(qt_signal)#define Q_EMIT#define METHOD(a)   qFlagLocation("0"#a QLOCATION)#define SLOT(a)     qFlagLocation("1"#a QLOCATION)#define SIGNAL(a)   qFlagLocation("2"#a QLOCATION)const char *qFlagLocation(const char *method){    QThreadData *currentThreadData = QThreadData::current(false);    if (currentThreadData != 0)        currentThreadData->flaggedSignatures.store(method);    return method;}

可以分析出signals限定了是public的，而发射信号emit就是调用信号函数
而我们在连接信号与槽时使用的SIGNAL和SLOT，就是一个代表方法的字符串

Qt类相关宏

#define Q_CLASSINFO(name, value)#define Q_PLUGIN_METADATA(x) QT_ANNOTATE_CLASS(qt_plugin_metadata, x)#define Q_INTERFACES(x) QT_ANNOTATE_CLASS(qt_interfaces, x)#ifdef Q_COMPILER_VARIADIC_MACROS# define Q_PROPERTY(...) QT_ANNOTATE_CLASS(qt_property, __VA_ARGS__)#else# define Q_PROPERTY(text) QT_ANNOTATE_CLASS(qt_property, text)#endif#define Q_PRIVATE_PROPERTY(d, text) QT_ANNOTATE_CLASS2(qt_private_property, d, text)#ifndef Q_REVISION# define Q_REVISION(v)#endif#define Q_OVERRIDE(text) QT_ANNOTATE_CLASS(qt_override, text)#define QDOC_PROPERTY(text) QT_ANNOTATE_CLASS(qt_qdoc_property, text)#define Q_ENUMS(x) QT_ANNOTATE_CLASS(qt_enums, x)#define Q_FLAGS(x) QT_ANNOTATE_CLASS(qt_enums, x)#define Q_ENUM_IMPL(ENUM) \    friend Q_DECL_CONSTEXPR const QMetaObject *qt_getEnumMetaObject(ENUM) Q_DECL_NOEXCEPT { return &staticMetaObject; } \    friend Q_DECL_CONSTEXPR const char *qt_getEnumName(ENUM) Q_DECL_NOEXCEPT { return #ENUM; }#define Q_ENUM(x) Q_ENUMS(x) Q_ENUM_IMPL(x)#define Q_FLAG(x) Q_FLAGS(x) Q_ENUM_IMPL(x)#define Q_SCRIPTABLE QT_ANNOTATE_FUNCTION(qt_scriptable)#define Q_INVOKABLE  QT_ANNOTATE_FUNCTION(qt_invokable)#define Q_SIGNAL QT_ANNOTATE_FUNCTION(qt_signal)#define Q_SLOT QT_ANNOTATE_FUNCTION(qt_slot)

其中Q_PROPERTY定义了Qt的属性系统，Q_ENUMS、Q_FLAGS定义了Qt的枚举类型操作

Qt翻译宏

#define QT_TR_FUNCTIONS \    static inline QString tr(const char *s, const char *c = Q_NULLPTR, int n = -1) \        { return staticMetaObject.tr(s, c, n); } \    QT_DEPRECATED static inline QString trUtf8(const char *s, const char *c = Q_NULLPTR, int n = -1) \        { return staticMetaObject.tr(s, c, n); }

Q_OBJECT宏

#define Q_OBJECT \public: \    static const QMetaObject staticMetaObject; \    virtual const QMetaObject *metaObject() const; \    virtual void *qt_metacast(const char *); \    virtual int qt_metacall(QMetaObject::Call, int, void **); \    QT_TR_FUNCTIONS \private: \    static void qt_static_metacall(QObject *, QMetaObject::Call, int, void **);

Q_OBJECT宏是Qt元对象模型Meta-Object Model的基础