scope resolution operator
时间: 2023-09-16 20:01:31 浏览: 53
作用域解析运算符(scope resolution operator)是一种用于访问类成员或命名空间成员的运算符,在C++语言中使用双冒号"::"表示。它的作用就是指定所要使用的变量、函数、类等在哪个作用域中。
在C++中,当有一个变量、函数、类等名称在不同的作用域中都存在时,使用作用域解析运算符可以明确地指定使用哪个作用域中的成员。例如,当一个类中有一个成员函数与全局函数同名时,我们可以使用作用域解析运算符来区分两者,比如"类名::成员函数名"表示类中的成员函数,"::全局函数名"表示全局函数。
此外,作用域解析运算符还可以用于访问命名空间中的成员。命名空间是一种将全局作用域划分为更小作用域的机制,防止不同库或代码中同名的函数、变量等产生冲突。当需要访问不同命名空间中的同名成员时,可以使用作用域解析运算符指定所要使用的命名空间。
总之,作用域解析运算符在C++中起到了明确指定成员所在作用域的作用,能够解决不同作用域中同名成员的访问冲突,提高了程序的可读性和灵活性。
相关问题
Which is used to define the member of a class externally? a. : b. :: c. # d. !!$
b. ::
The scope resolution operator `::` is used to define a member of a class externally in C++. This allows the definition of a member function or a static data member to be separate from its declaration in the class definition.
For example:
```
class MyClass {
public:
void myFunction(); // declaration
static int myStaticVariable; // declaration
};
// definition of myFunction
void MyClass::myFunction() {
// function body
}
// definition of myStaticVariable
int MyClass::myStaticVariable = 0;
```
In the example above, `myFunction` and `myStaticVariable` are declared in the class definition, but their definitions are provided externally using the scope resolution operator `::`. This allows the implementation of the member functions and static data members to be separated from the class definition, which can make the code easier to manage and understand.
error: in-class initialization of static data member
If you get an error message "in-class initialization of static data member" while trying to initialize a static data member inside a class definition, it means that you are using a version of C++ that does not support this feature.
In-class initialization of static data members was introduced in C++11, so if you are using an older version of C++, you will need to initialize your static data member outside the class definition.
Here's an example of how to initialize a static data member outside the class definition:
```c++
class MyClass {
public:
static int myStaticData; // declaration
};
int MyClass::myStaticData = 42; // initialization outside the class definition
```
In this example, we declare the static data member `myStaticData` inside the class definition, and then initialize it outside the class definition using the scope resolution operator `::`.
Note that if you are using a modern version of C++ that supports in-class initialization of static data members, you can still choose to initialize your static data member outside the class definition if you prefer.