混淆C ++指针和参考主题 [英] Confusion over C++ pointer and reference topic

问题描述

C ++中的以下参数传递机制有什么区别？

What is the difference between the following parameter passing mechanisms in C++?

void foo(int &x) 
void foo(int *x)
void foo(int **x)
void foo(int *&x)

I'd like to know in which case the parameter is being passed by value or passed by reference.

推荐答案

void foo(int &x)

将引用传递给整数。这是一个输入/输出参数，可以像函数中的常规整数一样使用。值会传回给调用者。

passes a reference to an integer. This is an input/output parameter and can be used like a regular integer in the function. Value gets passed back to the caller.

void food(int *x)

将指针传递给整数。这是一个输入/输出参数，但它像一个指针一样使用，必须取消引用（例如 * x = 100; ）。您还需要检查它不为null。

passes a pointer to an integer. This is an input/output parameter but it's used like a pointer and has to be dereferenced (e.g. *x = 100;). You also need to check that it's not null.

void foo(int **x)

传递指向整数指针的指针。这是一个类型为整数指针的输入/输出参数。如果要更改整数值的值（例如 * x =& m_myInt; ），请使用此选项。

passes a pointer to a pointer to an integer. This is an input/output parameter of type integer pointer. Use this if you want to change the value of an integer point (e.g. *x = &m_myInt;).

void foo(int *&x)

将指向的指针传递给整数。如上所述，但不需要解引用指针变量（例如 x =& m_myInt; ）。

passes a reference to a pointer to an integer. Like above but no need to dereference the pointer variable (e.g. x = &m_myInt;).

希望有意义。我建议使用typedef来简化指针和引用符号的使用。

Hope that makes sense. I would recommend using typedefs to simplify the use of pointers and reference symbols.

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