QT笔记——Q_Q 和Q_D 学习

在源码中，我们会经常看到Q_Q 和 Q_D 这两个东西 ，很好奇，就去网上搜索了一些和 查看了一些源码 部分

Q_D相关宏

#define Q_D(Class) Class##Private * const d = d_func()

Q_D(Test)
//展开后 是一个 私有类的指针常量 
TestPrivate * const d = d_func();

d_func()

QScopedPointer<QPainterPathPrivate, QPainterPathPrivateDeleter> d_ptr;

QPainterPathData *d_func() const {
     return reinterpret_cast<QPainterPathData *>(d_ptr.data()); }

Q_DECLARE_PRIVATE(Class)

#define Q_DECLARE_PRIVATE(Class) \ inline Class##Private* d_func() \ {
       Q_CAST_IGNORE_ALIGN(return reinterpret_cast<Class##Private *>(qGetPtrHelper(d_ptr));) } \ inline const Class##Private* d_func() const \ {
       Q_CAST_IGNORE_ALIGN(return reinterpret_cast<const Class##Private *>(qGetPtrHelper(d_ptr));) } \ friend class Class##Private;


Q_DECLARE_PRIVATE(Test)
//展开后
 inline TestPrivate* d_func() {
    return reinterpret_cast<TestPrivate *>(qGetPtrHelper(d_ptr));}
 inline const TestPrivate* d_func() const{
    return reinterpret_cast<const TestPrivate *>(qGetPtrHelper(d_ptr));}
 friend class TestPrivate;

Q_Q相关宏

#define Q_Q(Class) Class * const q = q_func()

**Q_DECLARE_PUBLIC(Class) **

#define Q_DECLARE_PUBLIC(Class) \ inline Class* q_func() {
       return static_cast<Class *>(q_ptr); } \ inline const Class* q_func() const {
       return static_cast<const Class *>(q_ptr); } \ friend class Class;

Q_DECLARE_PUBLIC(Test)  
    inline Test* q_func() {
     return static_cast<Test*>(q_ptr); } 
    inline const Test* q_func() const {
     return static_cast<const Test*>(q_ptr); } 
    friend class Test;