为什么解引用字符串向量迭代器需要括号？

Question

vector<string> MyStrings;
vector<string>::iterator ItStr;

I'm using c_str() to return the pointer to the string.

Why does it need to be dereferenced with parentheses?

Doesn't compile: *ItStr.c_str();

error C2039: 'c_str': is not a member of 'std::vector<_Ty>::iterator'

Compiles/Works with parentheses around iterator: (*ItStr).c_str();

If you could point me (no pun intended) in the right direction I would appreciate it.Thanks!

Answer 1

. has higher precedence than the unary * .

*ItStr.c_str() is as if you had said *(ItStr.c_str()) .

You can, of course, just use ItStr->c_str() , since (*x).y is equivalent to x->y (at least for pointers and iterators; you can, of course, overload the operators for your own types such that they are not consistent, but you'd be crazy to do so).

Answer 2

Because the . operator has precedence over the * operator. See this link

Answer 3

Without the brackets, *ItStr.c_str(); is interpreted as:

*(ItStr.c_str());

which obviously is wrong, and which you perhaps didn't intend. Its interpreted that way, because . operator has higher precedence than * operator. To avoid that you need to use brackets here:

(*ItStr).c_str();

So that it can be interpreted correctly - the way you intend it to be interpreted.

Have a look at:

• C++ Operator Precedence Table

Answer 4

Without the parentheses you are trying to dereference the entire statement ItStr.c_str() .

With the parens around *ItStr , you're dereferencing ItStr and then taking the .c_str() member of it. The arrow operator -> can also be used in place of putting the parentheses around the dereferenced ItStr .

As James et al have pointed out, it's an operator precedence issue.