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".
CodePudding user response：
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
})
}