C++中的 . -> ::
a::b is only used if b is a member of the class (or namespace) a. That is, in this case a will always be the name of a class (or namespace).
a.b is only used if b is a member of the object (or reference to an object) a. So for a.b, a will always be an actual object (or a reference to an object) of a class.
a->b is, originally, a shorthand notation for (*a).b it is a combination of dereferencing and member access.
However, -> is the only of the member access operators that can be overloaded, so if a is an object of a class that overloads operator-> (common such types are smart pointers and iterators), then the meaning is whatever the class designer implemented. To conclude: With a->b, if a is a pointer, b will be a member of the object the pointer a refers to. If, however, a is an object of a class that overloads this operator, then the overloaded operator function operator->() gets invoked.
a :: b 当b是一个类或namespace的成员，a是那个对象或namespace
a.b 当b是一个对象a的成员，对于a.b，a总是那个类的对象。
a->b 和 (*a).b 可以互换， a是一个指针，b则是指针指向的对象
include <iostream>
using namespace std;
class SomeClass{
public
int mydata;
bool someTruth;
SomeClass(){
mydata = 0;
someTruth = false;
}
};
int main(){
SomeClass mySomeClass; // Not a pointer...
SomeClass *pSomeClass; // we defined the pointer.
pSomeClass = new SomeClass; // we allocate the pointer.
// accessing the stuff beyond the pointer.
pSomeClass->mydata = 10; // we assigned mydata, the object's member, to 10.
pSomeClass->someTruth = true; // now we made someTruth, the object's member, to true
// the previous too lines are basically similar to
mySomeClass.mydata = 10;
mySomeClass.someTruth = true;
// assign accessing the member of the pointer of SomeClass
if(pSomeClass->someTruth == true)
{
cout << "pSomeClass->someTruth was True" << endl;
}
// clean up the pointer
delete pSomeClass;
return 0;
问题与思考
什么时候使用pointer，什么时候直接定义?
