在给函数使用原始变量时，更好的做法是什么:
unsigned long x = 4;
void func1(unsigned long& val) {
val = 5;
}
func1(x);
or:
void func2(unsigned long* val) {
*val = 5;
}
func2(&x);
勒夫:有什么理由选择一个而不是另一个吗?
当前回答
指针:
可以被分配为nullptr(或NULL)。 在调用站点，如果你的类型本身不是指针，你必须使用&， 显式地修改对象。 指针可以被反弹。
引用:
不能为空。 一旦被束缚，就无法改变。 调用者不需要显式地使用&。有时这被认为是 不好，因为你必须去函数的实现看看 完成参数的修改。
其他回答
引用是隐式指针。基本上，你可以改变引用指向的值，但你不能改变引用指向其他东西。因此，我的观点是，如果你只想改变一个参数的值，将其作为引用传递，但如果你需要改变参数以指向一个不同的对象，则使用指针传递它。
指针
A pointer is a variable that holds a memory address. A pointer declaration consists of a base type, an *, and the variable name. A pointer can point to any number of variables in lifetime A pointer that does not currently point to a valid memory location is given the value null (Which is zero) BaseType* ptrBaseType; BaseType objBaseType; ptrBaseType = &objBaseType; The & is a unary operator that returns the memory address of its operand. Dereferencing operator (*) is used to access the value stored in the variable which pointer points to. int nVar = 7; int* ptrVar = &nVar; int nVar2 = *ptrVar;
参考
A reference (&) is like an alias to an existing variable. A reference (&) is like a constant pointer that is automatically dereferenced. It is usually used for function argument lists and function return values. A reference must be initialized when it is created. Once a reference is initialized to an object, it cannot be changed to refer to another object. You cannot have NULL references. A const reference can refer to a const int. It is done with a temporary variable with value of the const int i = 3; //integer declaration int * pi = &i; //pi points to the integer i int& ri = i; //ri is refers to integer i – creation of reference and initialization
我的经验法则是:
如果你想对指针进行算术运算(例如，增加指针地址以遍历数组)，或者如果你必须传递一个空指针，请使用指针。
否则使用引用。
如果你要修改变量的值，你应该传递一个指针。 尽管在技术上传递引用或指针是相同的，但在用例中传递指针更具有可读性，因为它“通告”了函数将更改值的事实。
我真的认为你将受益于建立以下函数调用编码指南:
As in all other places, always be const-correct. Note: This means, among other things, that only out-values (see item 3) and values passed by value (see item 4) can lack the const specifier. Only pass a value by pointer if the value 0/NULL is a valid input in the current context. Rationale 1: As a caller, you see that whatever you pass in must be in a usable state. Rationale 2: As called, you know that whatever comes in is in a usable state. Hence, no NULL-check or error handling needs to be done for that value. Rationale 3: Rationales 1 and 2 will be compiler enforced. Always catch errors at compile time if you can. If a function argument is an out-value, then pass it by reference. Rationale: We don't want to break item 2... Choose "pass by value" over "pass by const reference" only if the value is a POD (Plain old Datastructure) or small enough (memory-wise) or in other ways cheap enough (time-wise) to copy. Rationale: Avoid unnecessary copies. Note: small enough and cheap enough are not absolute measurables.
