在 C++ 中的类声明中声明的函数如何执行？

Question

Some code contains function invoked inside class declaration.

class Example
{
   public:
    bool keyBlobClosed = deviceClosed()?true:false;
};

In this case, deviceClosed() function gets executed when object created or when class declaration created in memory?

Answer 1

This is called a default member initializer . It is allowed on non-static members (as you have used here) since C++11.

It is equivalent to providing a member initializer list that performs the same initialization:

class Example {
public:
    bool keyBlobClosed;
    Example() 
        : keyBlobClosed(deviceClosed())
    {
    }
};

Obviously, this will cause deviceClosed() to be called whenever Example is instantiated. The return value of deviceClosed() will be used to initialize keyBlobClosed.