1.在数组或者字典中查找元素时，没有查到系统用NSNotFound表示。比如下面例子，应该养成这种编程习惯，可以减少因为’超标’而闪退的情况。
if ([self.departmentNameArray indexOfObject: self.applicationcreatorModel.departmentName] == NSNotFound)
if ([self.departmentNameArray indexOfObject: self.applicationcreatorModel.departmentName] == NSNotFound)