英文:
How to assign an interface variable to the value stored by another
问题
问题描述：
args[0] = ... 更新了args[0]的值：
package main
import "fmt"
func MyFunc(lambda any) {
myVars := []any {0}
for i := 0; i < 30; i++ {
lambda.(func(...any))(myVars...)
fmt.Println(myVars[0]) // 0, 2, 4, ..., 60 (good)
}
}
func main() {
MyFunc(func(args ...any) {
args[0] = args[0].(int) + 2
})
}
但是当我创建变量v := args[0]并尝试通过v = ...来更新args[0]的值时，Go语言（可以理解）将v重新赋值为一个新对象，而不是更新args[0]的值：
package main
import "fmt"
func MyFunc(lambda any) {
myVars := []any {0}
for i := 0; i < 30; i++ {
lambda.(func(...any))(myVars...)
fmt.Println(myVars[0]) // 0, 0, 0, ..., 0 (bad)
}
}
func main() {
MyFunc(func(args ...any) {
v := args[0]
v = v.(int) + 2
})
}
我的问题是：
如何使用v来更新args[0]的值？非常感谢任何帮助。
我尝试过的方法：
我不能使用*v = ...，因为这会导致编译错误"invalid operation: cannot indirect v (variable of type any)"。
我不能使用v := args[0].(*int); *v = *v + 2;，因为这会导致运行时错误"panic: interface conversion: interface {} is int, not *int"。
英文:
Description of the problem:
args[0] = ... updates args[0]:
package main
import "fmt"
func MyFunc(lambda any) {
myVars := []any {0}
for i := 0; i < 30; i++ {
lambda.(func(...any))(myVars...)
fmt.Println(myVars[0]) // 0, 2, 4, ..., 60 (good)
}
}
func main() {
MyFunc(func(args ...any) {
args[0] = args[0].(int) + 2
})
}
But when I make variable v := args[0] and attempt to update the value of args[0] by doing v = ..., Go (understandably) reassigns v to a new object rather than updating the value of args[0]:
package main
import "fmt"
func MyFunc(lambda any) {
myVars := []any {0}
for i := 0; i < 30; i++ {
lambda.(func(...any))(myVars...)
fmt.Println(myVars[0]) // 0, 0, 0, ..., 0 (bad)
}
}
func main() {
MyFunc(func(args ...any) {
v := args[0]
v = v.(int) + 2
})
}
My question:
How, using v, can I update args[0]? Any help will be greatly appreciated.
Things I have tried:
I cannot do *v = ..., as this yields compiler error "invalid operation: cannot indirect v (variable of type any)".
I cannot do v := args[0].(*int); *v = *v + 2;, as this yields runtime error "panic: interface conversion: interface {} is int, not *int".
答案1
得分: 3
你没有正确执行指针操作。请对指针变量v进行类型断言。首先使用&获取arg值的地址，然后继续执行你的逻辑。
func main() {
MyFunc(func(args ...any) {
v := &args[0]
*v = (*v).(int) + 2
})
}
英文:
You did not do the pointer operations correctly. Type-assert the pointer variable v. First take the address of the arg value with &, then proceed with rest of your logic.
func main() {
MyFunc(func(args ...any) {
v := &args[0]
*v = (*v).(int) + 2
})
}
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