Golang将一个项目追加到一个切片

问题描述

为什么 Test 函数的参数在调用者的作用域中接收变量 a 的副本。

由于slice变量包含一个slice描述符，它只是引用一个底层数组，在 Test code>函数可以连续多次修改 slice 变量中保存的切片描述符，但这不会影响调用者及其一个变量。

在 Test 函数中，第一个 append 重新分配 slice 变量下的backing数组，将其原始内容复制到 100 就可以了，这就是你正在观察的。从 Test 退出时， slice 变量超出范围，并且切片引用的（新）底层数组。

如果您想使 Test 的行为类似于 append ，您必须从中返回新片 —就像追加一样 - —并要求 Test 的调用者以与他们使用 append 相同的方式使用它：

  func Test（slice [] int）[] int {
 slice = append（slice，100）
 
 fmt.Println（slice）
 
 return slice 
} 
 
a =测试（a）
  

请详细阅读基本上向您展示了如何在解释slice如何在内部工作之后，手动实现 append 。然后阅读。

Why does a remain the same? Does append() generate a new slice?

package main

import (
    "fmt"
)

var a = make([]int, 7, 8)

func Test(slice []int) {
    slice = append(slice, 100)
    fmt.Println(slice)
}

func main() {
    for i := 0; i < 7; i++ {
        a[i] = i
    }

    Test(a)
    fmt.Println(a)
}

解决方案

In your example the slice argument of the Test function receives a copy of the variable a in the caller's scope.

Since a slice variable holds a "slice descriptor" which merely references an underlying array, in your Test function you modify the slice descriptor held in the slice variable several times in a row, but this does not affect the caller and its a variable.

Inside the Test function, the first append reallocates the backing array under the slice variable, copies its original contents over, appends 100 to it, and that's what you're observing. Upon exiting from Test, the slice variable goes out of scope and so does the (new) underlying array that slice references.

If you want to make Test behave like append, you have to return the new slice from it — just like append does — and require the callers of Test to use it in the same way they would use append:

func Test(slice []int) []int {
    slice = append(slice, 100)

    fmt.Println(slice)

    return slice
}

a = Test(a)

Please read this article thoroughly as it basically shows you how to implement append by hand, after explaining how slices are working internally. Then read this.

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