package main
func main() {
x := []int{7, 8, 9}
y := [3]*int{}
for i, v := range x {
defer func() {
print(v)
}()
y[i] = &i
}
print(*y[0], *y[1], *y[2], " ")
}
Choices:
Answer: 222 999 (before Go 1.22), 012 987 (since Go 1.22)
Run it on Go play.
Key points:
i and v)
are shared by all loop steps. In other words, each iteration variable only has
one instance during the execution of the loop.
That means all the elements of y
store the same address (of the value v).
In the end, the variable i is set as 2,
and the variable v is set as 9.
So, prior to Go 1.22, the output is 222 999.
i and v)
will get new instances at each loop step. So, since Go 1.22, the output is 222 999.
Different from the above program, the following program always prints 012 987,
either prior to or since Go 1.22.
package main
func main() {
x := []int{7, 8, 9}
y := [3]*int{}
for i, v := range x {
defer print(v)
i := i
y[i] = &i
}
print(*y[0], *y[1], *y[2], " ")
}
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