对于
Windows,Mac和iOS,以下代码编译时没有警告：
class MyClass {
SomeOtherClass * m_object;
void (SomeOtherClass::*m_callback)();
public:
MyClass(SomeOtherClass * _object,void (SomeOtherClass::*_callback)()=NULL) :
m_object(_object),m_callback(_callback) {}
void DoStuff() {
//generates warning: NULL used in arithmetic when compiling with the Android NDK
if (NULL==m_callback) {
m_object->DoNormalCallback();
} else {
(m_object->*m_callback)();
}
}
};
为什么会产生警告,我该怎么办呢？
解决方法
我不认为你可以将0(或NULL)与成员函数指针进行比较,特别是因为它们可能实际上不是指针(例如,当函数是虚函数时).
就个人而言,我会在没有比较的情况下重写if测试,例如：
void DoStuff() {
if (m_callback) {
(m_object->*m_callback)();
} else {
m_object->DoNormalCallback();
}
}
并且,对于奖励积分,在构造函数中执行此测试.
class MyClass {
SomeOtherClass * m_object;
void (SomeOtherClass::*m_callback)();
public:
MyClass(SomeOtherClass * _object,m_callback(_callback)
{
// Use "DoNormalCallback" unless some other method is requested.
if (!m_callback) {
m_callback = &SomeOtherClass::DoNormalCallback;
}
}
void DoStuff() {
(m_object->*m_callback)();
}
};
