何时在游戏开发中使用C ++指针

Question

I've looked at a bunch of articles, and most tell the same story: don't use pointers unless you have to. Coming from a C#/Java background where memory is all managed, I have absolutely no idea when it's appropriate to use a pointer, except for these situations:

• dynamic memory (like variable-size arrays)
• polymorphism

When else would I use pointers, especially in the context of gamedev?

Answer 1

"Don't use pointers, they're slow" doesn't make sense (at least not in C++).

It's exactly like saying, "Don't use variables, they're slow" .

• Did you mean, "Don't use dynamic memory allocation "?
  If so: I don't think you should worry about it right now. Write the code first, then optimize later.

• Or did you mean to say, "Don't use raw pointers (ie of type foo* )", which would require new and delete ?
  If so, that is good advice : You generally want smart pointers instead, like shared_ptr or unique_ptr , to manage objects, instead of dealing with raw pointers. You shouldn't need to use new and delete in most C++ code, even though that might seem natural.
  But they're still pointers under the hood!

• Or did you mean something else?

Addendum

Thanks to the @bames53 below for pointing this out:

If passing a copy is an option (ie when you're passing small amounts of data, not a huge structure or an array that could be larger than a few registers, eg on the order of ~16 bytes), do not use pointers (or references) to pass data; pass by copy instead. It allows the compiler to optimize better that way.

Answer 2

One primary use of pointers (although references are generally better when possible), is to be able to pass an object around without copying it. If an object contains a lot of data, copying it could be quite expensive and unnecessary. In terms of game development, you can store pointers in a container like a std::vector so you can manage objects in a game. For instance, you could have a vector that contains pointers to all enemies in the game so you can perform some "mass procedure" on them. It might be worthwhile to look into smart pointers , too, since these could make your life a lot easier (they help a great deal when it comes to preventing memory leaks).

Answer 3

The idea is that you don't want to have memory leaks, nor slow down the program while retrieving memory, so, if you pre-allocate the structures you will need, then you can use pointers to pass the structures around, as that will be faster than copying structures.

I think you are just confused as to why pointers may be considered bad, as there are many places to use them, you just need to think about why you are doing it.

Answer 4

You don't need pointers for variable size arrays, you can (and usually should) use std::vector instead. You don't need raw pointers for polymorphism either; virtual functions work with smart pointers like unique_ptr .

In modern C++ you rarely need pointers. Often they will be hidden away inside resource owning classes like vectors. To pass objects around without copying them you can use references instead. Most of the remaining uses of pointers are covered by smart pointers. Very rarely you will want a 'non-owning' pointer, in which case raw pointers are fine.

You'll learn the appropriate uses of pointers if you learn about the things to should use instead of pointers. So learn about RAII, references, and smart_pointers.