QT 关联QComboBox的currentIndexChanged时遇到 成员指针指向重载指针函数问题

主要解决信号槽connect链接时，信号有多个重载，如何告诉编译器使用那个重载。
在项目中动态添加了一个QComboBox,在当准备关联currentIndexChanged信号到某个成员函数中时,发现currentIndexChanged有两个重载:

    void currentIndexChanged(int index);
    void currentIndexChanged(const QString &);

如果直接关联，例:

connect(comboBox, &QComboBox::currentIndexChanged,this,  &Dialog::comBoxChangeIndex);

 

　会报:

error: no matching member function for call to 'connect'

20220331： 推荐使用QT提供的QOverload类解决重载问题，跳转到此篇末尾查看

需要把对应的函数强转一下，指定使用currentIndexChanged函数的那个重载:

connect(comboBox, (void (QComboBox::*)(int))&QComboBox::currentIndexChanged, this, (void (Dialog::*)(int))&Dialog::comBoxChangeIndex);

connect(comboBox, (void (QComboBox::*)(int))&QComboBox::currentIndexChanged, this, (void (Dialog::*)(int))&Dialog::comBoxChangeIndex);

这样，就指定了要用QComboBox的currentIndexChanged(int)重载,如果想使用currentIndexChanged(const QString &)重载,把(void (QComboBox::*)(int))改成(void (QComboBox::*)(const QString &))

20220331： 正确做法应该使用QT的QOverload类实现，在随笔最下边查看详细用法。

例:

  connect(combobox, (void (QComboBox::*)(int))&QComboBox::currentIndexChanged, this, (void (Setting::*)(int))&Setting::typeComBoxCurrentIndexChanged);
  connect(combobox, (void (QComboBox::*)(const QString &))&QComboBox::currentIndexChanged, this, (void (Setting::*)(QString))&Setting::typeComBoxCurrentIndexChanged);

这里Setting类的typeComBoxCurrentIndexChanged函数也有两个重载，对应QComboBox的currentIndexChanged函数两个重载。

void typeComBoxCurrentIndexChanged(int)
void typeComBoxCurrentIndexChanged(QString)

 

20220331：
以上是通过强转来告诉编译器使用那个重载函数，正确的做法是使用QT提供的QOverload类来实现，例如想使用currentIndexChanged const QString&重载：

    connect(ui->comboBox, QOverload<const QString&>::of(&QComboBox::currentIndexChanged), [](const QString & value){
        
    });

或者使用currentIndexChanged int Index 重载:

    connect(ui->comboBox, QOverload<int>::of(&QComboBox::currentIndexChanged), [](int intdex){
        
    });