How do I understand this static casting ?

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I have a problem with understanding the following line of code:

static_cast<void(QButtonGroup::*)(QAbstractButton *, bool)>(&QButtonGroup::m_buttonGroup)

What I have tried:

I searched for the static_cast, and understand it, i know that in this code we are trying to convert the object

(&QButtonGroup::m_buttonGroup)

to another type:

<void(QButtonGroup::*)(QAbstractButton *, bool)>

But i do not understand the previous line.what do we mean by:

void(QButtonGroup::*)(QAbstractButton *, bool)

this supposed to be a type, but i can not get it?
Thanks in advance.

Posted 14-Aug-18 0:57am

Ahmed AE

Updated 14-Aug-18 6:34am

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Richard MacCutchan · Accepted Answer · 2018-08-14T06:35:00

C++

static_cast<void(QButtonGroup::*)(QAbstractButton *, bool)>(&QButtonGroup::m_buttonGroup)

Starting from the wrong end look at whatever is in the parentheses:

C++

&QButtonGroup::m_buttonGroup

m_buttonGroup is a static object, in the QButtonGroup class. And the & means use the address of this object. So that is the original item that is to be cast, to whatever is in the angle brackets (< >). The angle brackets contain:

C++

void(QButtonGroup::*)(QAbstractButton *, bool)

Which is a function pointer definition. The (QButtonGroup::*) part says this is a pointer to something in the QButtonGroup class. The parentheses around this tell us it's a function rather than a data pointer. The following parentheses contain the definition of the parameters to be passed to the function, and the preceding void part tells us that the function does not have a return type.

Without more context it's not possible to say more.