英文:
How to modify map in go
问题
我正在尝试修改"loopback"的IP地址，但似乎无法直接访问该元素。
addrs["loopback"][0] = byte(2) //无法对addrs["loopback"][0]赋值
在Go语言中，我该如何实现这个功能？
package main
import "fmt"
type IPAddr [4]byte
func main() {
addrs := map[string]IPAddr{
"loopback": {127, 0, 0, 1},
"googleDNS": {8, 8, 8, 8},
}
addrs["loopback"][0] = byte(2)
for n, a := range addrs {
fmt.Printf("%v: %v\n", n, a)
}
}
英文:
I am trying to modify the IPAddr for the "loopback", but it seems cannot access the element directly.
addrs["loopback"][0] = byte(2) //cannot assign to addrs["loopback"][0]
How can I do it within go?
package main
import "fmt"
type IPAddr [4]byte
func main() {
addrs := map[string]IPAddr{
"loopback": {127, 0, 0, 1},
"googleDNS": {8, 8, 8, 8},
}
addrs["loopback"][0] = byte(2)
for n, a := range addrs {
fmt.Printf("%v: %v\n", n, a)
}
}
答案1
得分: 3
因为映射值不可寻址，所以你需要重新分配整个值：
addr := addrs["loopback"]
addr[0] = 2
addrs["loopback"] = addr
如果你将映射值类型更改为*IPAddr，那么赋值语句
addrs["loopback"][0] = 2
就可以工作了。在这种情况下，代码是将值分配给映射所指向的值。这个值是可寻址的。
英文:
Because map values are not addressable, you need to reassign the entire value:
addr := addrs["loopback"]
addr[0] = 2
addrs["loopback"] = addr
If you change the map value type to *IPAddr, then the assignment
addrs["loopback"][0] = 2
works. In this case, the code is assigning to a value pointed to by the map. This value is addressable.
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