package main
import (
"fmt"
"sync"
)
type Data struct {
A []int32
B []string
}
func main() {
channel := make(chan Data)
data := Data{A: make([]int32, 0, 1), B: make([]string, 0, 1)}
fmt.Printf("Before gorountine addr, A: %p\n", data.A)
fmt.Printf("Before gorountine addr, B: %p\n", data.B)
wg := new(sync.WaitGroup)
wg.Add(1)
go func() {
for d := range channel {
fmt.Printf("goroutine addr before append, A: %p\n", d.A)
fmt.Printf("goroutine addr before append, B: %p\n", d.B)
d.A = append(d.A, 23)
d.B = append(d.B, "23")
//d.A[0] = 23
//d.B[0] = "23"
fmt.Printf("goroutine addr after append, A: %p\n", d.A)
fmt.Printf("goroutine addr after append, B: %p\n", d.B)
fmt.Println(d)
}
wg.Done()
}()
fmt.Printf("Before: %v\n", data)
channel <- data
close(channel)
wg.Wait()
fmt.Printf("After gorountine addr, A: %p\n", data.A)
fmt.Printf("After gorountine addr, B: %p\n", data.B)
fmt.Printf("After: %v\n", data)
}
代码见上
输出见下：
Before gorountine addr, A: 0xc20800a1dc
Before gorountine addr, B: 0xc20800a200
Before: {[] []}
goroutine addr before append, A: 0xc20800a1dc
goroutine addr before append, B: 0xc20800a200
goroutine addr after append, A: 0xc20800a1dc
goroutine addr after append, B: 0xc20800a200
{[23] [23]}
After gorountine addr, A: 0xc20800a1dc
After gorountine addr, B: 0xc20800a200
After: {[] []}
我的问题是：为什么slice的地址没有变，但是master goroutine里的data数据为空？
如果我去掉append，改为直接赋值，最后data则不为空
需要注意的是，我在make slice的时候特地设置cap为1
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