什么时候是一个指针习惯？ [英] When is a pointer idiomatic?
问题描述
我来自没有显式指针的语言，所以我不太了解它们存在的意义（没有双关语意思）。
问题是我不知道，大多数时候，我为什么传递一个指针函数。我明白，当你传递一个指针时，对变量的修改会在任何地方完成，但是有什么意义呢？为什么不只是修改值并返回结果？
例如， http.HandlerFunc 是一个接收 http.ResponseWriter 和 * http.Request 作为参数。我已经读过界面实际上是指针（是吗？），但我没有得到的是，为什么？
为什么我得到一个指向作家？我没有修改它，我只是写信给它。而且，为什么我得到一个指向请求的指针？我正在做的东西像 request.FormValue（）。
我想通过这些来确定例子，这个问题的答案是我什么时候需要传入一个指针？。
我现在正在编写代码，尝试编译它，通过添加一个&符号和星号来修正我必须传入指针的错误，直到错误通过。不过，我觉得这种半知半懂的指针概念很快就会在我的背后咬我一口。
可以将指针看作指向对象内存地址的值。与大多数数据结构相比，指针很小（比如说8字节）。
很多时候你会得到一个指向对象的指针，因为通过这些指针要快得多字节，而不是创建要传递的整个对象的副本。
对于Request对象，创建请求下的所有内容（payload，headers和whatnot）相比，只需传递一个可访问原始数据的指针。
I come from languages which don't have explicit pointers, so I don't really understand the point of their existence (no pun intended).
The problem is that I have no idea, most of the time, why I am passing a pointer to a function. I do understand that when you pass in a pointer, modifications to the variable are done to the value everywhere, but what's the point? Why not just modify the value and return the result?
For example, http.HandlerFunc is a function that receives http.ResponseWriter and *http.Request as arguments. I have read that interfaces are in fact pointers (is that right?), but what I'm not getting is, why?
Why am I getting a pointer to a writer? I'm not modifying it, I'm merely writing to it. And, why am I getting a pointer to a request? I am doing stuff like request.FormValue().
What I'm trying to determine here, through these examples, is the answer to the question, "when do I need to pass in a pointer?"
The way I do it right now is to write my code, try to compile it, fix the errors that say I must pass in a pointer by adding an ampersand and asterisk, until the errors pass. However, I feel this half-understood concept of pointers is going to bite me in the backside some day very soon.
You can think of a pointer as a value that points to the memory address of an object. Pointers are small (say 8 bytes) compared to most data structures.
A lot of times you will get a pointer to an object because it is much faster to pass those 8 bytes than to create a copy of the entire object that you want to pass.
In the case of a Request object it would be very expensive to create a copy of everything under the request (the payload, headers, and whatnot) compared to just passing a pointer that has access to the original data.
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