访问嵌入式结构值时索引超出范围错误

Question

I get an out of range error when I run this code:

Go:

type Ping struct {
    Content []aContent
}

type aContent struct {
    Type        string
    Id          string
    Created_at  int64
}

var p Ping

func main() {

f := Ping{Content: []aContent{{Type: "Hello", Id: "asdf"}}}
fmt.Println(f)
fmt.Println(p.Content[0].Created_at) //what's wrong?
}

What's wrong? The code can be found here: http://play.golang.org/p/uZm5LaUuGW

Answer 1

variable p of type Ping and its field/property Content is un-initialized, so when you access the content of the Content which is a slice, it throws you that error. Why? Because the value of an uninitialized slice is nil. i.e p.Content == []