在POP源代码中如下代码片段：
struct _POPPropertyAnimationState : _POPAnimationState
{
NSUInteger valueCount;
valueCount(nil)
}
使用Xcode6.0.1打开项目会出现如下截图错误(Xcode5中不会出现)：
错误信息：Cannot initialize a member subobject of type ‘NSUInteger‘ (aka ‘unsigned long‘) with an rvalue of type ‘nullptr_t‘
将valueCount初始化为valueCount(0)后，问题解决了。
struct _POPPropertyAnimationState : _POPAnimationState
{
NSUInteger valueCount;
valueCount(0)
}
原文：http://www.cnblogs.com/samniu/p/4028357.html