Hi, I have this example:
package main
import (
"fmt"
"time"
)
func main() {
fmt.Println("Simple test")
test(nil)
fmt.Println()
fmt.Println("Base test")
var b *base
b = nil
test(b)
fmt.Println()
time.Sleep(1 * time.Second)
fmt.Println("Sub test")
var s *sub
s = nil
test(s)
}
type inter interface {
Test()
}
type base struct {
}
func (i *base) Test() {
fmt.Printf("IMPL INVOKED ON NIL %s", i)
}
type sub struct {
base
}
func test(intr inter) {
if intr != nil {
fmt.Printf("Is not nil %v\n", intr)
intr.Test()
} else {
fmt.Printf("Is nil %v NOT INVOKED ON NIL \n", intr)
}
}
And get the following result:
Simple test
Is nil <nil> NOT INVOKED ON NIL
Base test
Is not nil <nil>
IMPL INVOKED ON NIL %!s(*main.base=<nil>)
Sub test
Is not nil <nil>
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x4014e5]
goroutine 1 [running]:
panic(0x4920c0, 0xc42000a0b0)
/usr/lib/go-1.7/src/runtime/panic.go:500 +0x1a1
main.(*sub).Test(0x0)
<autogenerated>:2 +0x5
main.test(0x4f9180, 0x0)
Could anyone explain why it happens? Why nil checking is working for the
first case and doesn't work for rest of cases?
Thanks!
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