dongxia2068 2016-11-09 19:27
浏览 239
已采纳

Golang将数组传递给函数并对其进行修改

In most languages (like c++) passing arrays result in implicitly passing it by a reference, so any changes to the passed array in the function will result in changing the original one. I am learning Golang, and In the book "The Go Programming Language" by Alan A.A. Donovan and Brian W. Kernighan It is said, that its behaviour is different from other languages - It does not implicitly pass array by reference.

It is confusing me a bit - doesn't that mean that passing an array without the reference should not modify the array itself? Let me illustrate that:

func main() {
    tab := []int{1, 2, 3}
    fmt.Println(tab)
    // Results in [1 2 3]
    reverse(tab)
    fmt.Println(tab)
    // Results in [3 2 1]
}

func reverse(tab []int) {
    for i, j := 0, len(tab)-1; i < j; i, j = i+1, j-1 {
        tab[i], tab[j] = tab[j], tab[i]
    }
}

In code above array is not passed by the reference, but the reverse function modifies the original one, so It works somewhat like C++ program would do. Could anyone explain me the difference?

PS: Sorry if it is a dummy question, I am totally new to the Golang and trying to understand the basics well.

  • 写回答

2条回答 默认 最新

  • dongmi8980 2016-11-09 19:43
    关注

    The explanation is rather simple: there isn't a single array declared or used explicitly in your code above. Your tab local variable and the tab parameter are slices.

    In Go the length of an array is part of the type, e.g. [3]int (this is true to an extent that for example [2]int and [3]int are 2 different / distinct array types). If the length is not present (either explicit like [2]int or implicit like in the composite literal [...]int{1, 2, 3}), then that is not an array type but a slice type.

    Yes, as you read, an array value means all its elements, and when passed around (or assigned), all its elements are copied. Slices however are just small descriptors, headers, describing a contiguous section of an array; and when slices are passed around (or assigned), only this header is copied (the pointer included), which will point to the same underlying array. And so if you modify the elements of the slice-copy, the changes will be reflected in the original slice as there is only one backing array that holds the elements.

    If you want to know what's in a slice header exactly, you may check out the reflect.SliceHeader type: it's a struct containing the pointer to the first element of the slice, the length and the capacity of the slice.

    Please read the following blog posts which explain this in great details:

    Go Slices: usage and internals

    Arrays, slices (and strings): The mechanics of 'append'

    Also see these related questions for more details:

    Why have arrays in Go?

    Are golang slices pass by value?

    本回答被题主选为最佳回答 , 对您是否有帮助呢?
    评论
查看更多回答(1条)

报告相同问题?

悬赏问题

  • ¥15 elasticsearch
  • ¥30 python ttk 获取下拉框问题
  • ¥15 uniapp的uni-datetime-picker组件在ios端不适配
  • ¥15 前端 uniapp App端在离线状态如何使用modbus 连接手机蓝牙进行读写操控机器?
  • ¥15 SQL语句根据字段自动生成行
  • ¥500 “掌声响起来”软件(不确定性人工智能)
  • ¥500 我要找大模型一体机产品手册和应用案例
  • ¥20 关于游戏c++语言代码问题
  • ¥15 如何制作永久二维码,最好是微信也可以扫开的。(相关搜索:管理系统)
  • ¥15 delphi indy cookie 有效期