Golang的range关键字如何正确使用 详解遍历时的值拷贝问题

package main

import "fmt"

func main() {
    arr := []int{1, 2, 3, 4, 5}

    fmt.Println("Original array:", arr)

    for i, v := range arr {
        v *= 2 // 修改的是v的拷贝
        fmt.Printf("Index: %d, Value: %d\n", i, v)
    }

    fmt.Println("Modified (but not really) array:", arr) // 原始数组未改变

    // 如果想要修改原始数组，需要使用索引
    for i := range arr {
        arr[i] *= 2 // 通过索引修改原始数组
    }

    fmt.Println("Truly modified array:", arr)
}

package main

import "fmt"

func main() {
    str := "Hello, 世界!"

    for i, r := range str {
        fmt.Printf("Index: %d, Rune: %c, Unicode: %U\n", i, r, r)
    }
}

package main

import "fmt"

func main() {
    m := map[string]int{"a": 1, "b": 2, "c": 3}

    for k, v := range m {
        fmt.Printf("Key: %s, Value: %d\n", k, v)
    }
}

package main

import "fmt"

func main() {
    ch := make(chan int, 5)
    ch <- 1
    ch <- 2
    ch <- 3
    close(ch) // 关闭通道

    for v := range ch {
        fmt.Println("Received:", v)
    }
}

package main

import "fmt"

func main() {
    s := []int{1, 2, 3}
    fmt.Println("Original slice:", s)

    for i, v := range s {
        fmt.Printf("Index: %d, Value: %d\n", i, v)
        s = append(s, i+v) // 修改切片长度
    }

    fmt.Println("Modified slice:", s)
}

package main

import (
    "fmt"
    "sync"
)

func main() {
    nums := []int{1, 2, 3, 4, 5}
    var wg sync.WaitGroup

    for _, num := range nums {
        wg.Add(1)
        go func(n int) {
            defer wg.Done()
            fmt.Printf("Goroutine processing: %d\n", n)
        }(num) // 将num作为参数传递给goroutine
    }

    wg.Wait()
    fmt.Println("All goroutines finished.")
}