Multiple using Statements

Yes, you can have multiple using statements for the same namespace in different scopes. The using statement only applies to the scope in which it appears and any nested scopes.

If you have multiple using statements for the same namespace in different scopes, each one will apply only to its own scope and any nested scopes.

For example:

1#include <iostream>
2
3namespace MyNamespace {
4  void Foo() {
5    std::cout << "MyNamespace::Foo()\n";
6  }
7}
8
9void Function1() {
10  using MyNamespace::Foo;
11
12  // Calls MyNamespace::Foo()
13  Foo();
14}
15
16void Function2() {
17  // No using statement here
18  // Explicit namespace qualifier needed
19  MyNamespace::Foo();
20}
21
22int main() {
23  using MyNamespace::Foo;
24  Foo();// Calls MyNamespace::Foo()
25  Function1();
26  Function2();
27}

1MyNamespace::Foo()
2MyNamespace::Foo()
3MyNamespace::Foo()

The using statement in Function1 applies only within that function, while the using statement in main applies to main and any functions called from main that don't have their own using statements.