英文:
Can't assign to struct variable
问题
我有一个地图
var users = make(map[int]User)
我正在填充地图，一切都很好。稍后，我想给User的一个值赋值，但是我得到了一个错误。
type User struct {Id intConnected bool}users[id].Connected = true // 错误
我还尝试编写一个函数来赋值，但也不起作用。
英文:
I've got a map
var users = make(map[int]User)
I'm filling the map and all is fine. Later, I want to assign to one of the values of User, but I get an error.
type User struct {Id intConnected bool}users[id].Connected = true // Error
I've also tried to write a function that assigns to it, but that doesn't work either.
答案1
得分: 8
例如，
package mainimport "fmt"type User struct {Id intConnected bool}func main() {users := make(map[int]User)id := 42user := User{id, false}users[id] = userfmt.Println(users)user = users[id]user.Connected = trueusers[id] = userfmt.Println(users)}
输出：
map[42:{42 false}]map[42:{42 true}]
英文:
For example,
package mainimport "fmt"type User struct {Id intConnected bool}func main() {users := make(map[int]User)id := 42user := User{id, false}users[id] = userfmt.Println(users)user = users[id]user.Connected = trueusers[id] = userfmt.Println(users)}
Output:
map[42:{42 false}]map[42:{42 true}]
答案2
得分: 2
在这种情况下，将指针存储在映射中而不是结构体是有帮助的：
package mainimport "fmt"type User struct {Id intConnected bool}func main() {key := 100users := map[int]*User{key: &User{Id: 314}}fmt.Printf("%#v\n", users[key])users[key].Connected = truefmt.Printf("%#v\n", users[key])}
输出：
&main.User{Id:314, Connected:false}&main.User{Id:314, Connected:true}
英文:
In this case it is helpful to store pointers in the map instead of a structure:
package mainimport "fmt"type User struct {Id intConnected bool}func main() {key := 100users := map[int]*User{key: &User{Id: 314}}fmt.Printf("%#v\n", users[key])users[key].Connected = truefmt.Printf("%#v\n", users[key])}
Output:
&main.User{Id:314, Connected:false}&main.User{Id:314, Connected:true}
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论