golang 断言失败

var value interface{} = 42
intValue, ok := value.(int)
if ok {
    fmt.Printf("intValue is %d
", intValue)
} else {
    fmt.Println("value is not an integer")
}

type T1 struct {
    value bool 
}

type T2 struct {
    v T1
}

var t2 T2 = T2{T1{true}}

val, ok := (t2.v).(bool)
if ok {
    fmt.Println("val is", val) 
} else {
    fmt.Println("type assertion failed")
}

var value interface{} = 42

switch value.(type) {
case int:
    i := value.(int)
    fmt.Println("int", i)
case string:
    s := value.(string)
    fmt.Println("string", s)
default:
    fmt.Println("unknown type")
}

var ptr *int = nil
value, ok := interface{}(ptr).(*int)
if ok && value != nil {
    fmt.Println("the pointer is not nil")
} else {
    fmt.Println("the pointer is nil")
}

func safeConvertToInt(v interface{}) (int, error) {
    switch value := v.(type) {
    case int:
        return value, nil
    case float64:
        return int(value), nil
    case string:
        return strconv.Atoi(value)
    default:
        return 0, fmt.Errorf("unsupported type %T", v)
    }
}