golang从指针类型切片复制指针值
我有一个名为orderList的切片来记录订单。 现在我有了第一个订单,它的OtaBookID是“A123”,我想复制这个订单并将其OtaBookID更改为“B123”。ReseElement类型有一些其他详细信息来记录此订单,我将其隐藏,因为这不会影响我的问题。我可以成功更改Res.OtaBookID,但我不知道如何更改Res.StateDetail[0].Res.OtaBookIDgolang从指针类型切片复制指针值,go,Go,我有一个名为orderList的切片来记录订单。 现在我有了第一个订单,它的OtaBookID是“A123”,我想复制这个订单并将其OtaBookID更改为“B123”。ReseElement类型有一些其他详细信息来记录此订单,我将其隐藏,因为这不会影响我的问题。我可以成功更改Res.OtaBookID,但我不知道如何更改Res.StateDetail[0].Res.OtaBookID type Order struct { *Res Status int } type Res
type Order struct {
*Res
Status int
}
type Res struct {
ResID int64
OtaBookID string
StayDetail []*ResElement
TotalCharge float64
CustFName string
CustLName string
CreateTime time.Time
}
type ResElement struct {
Res *Res
OtaEleID string
OtaRoomID string
RoomID int
Arrival time.Time
Depart time.Time
Charge float64
CreateTime time.Time
}
我想要的结果是orderList[0].Res.OtaBookID和orderList[0].Res.StateDetail[0].Res.OtaBookID是“A123”,另一个是“B123”
ps:因为我正在接管别人的工作。所以这三种类型已经固定,无法调整。我想知道在这种情况下,是否有任何方法可以实现我的目标根据您的示例和说明,我们可以重点关注实现您目标的主要方面:
func main() {
var orderList []*Order
res := new(Res)
res.OtaBookID = "A123"
resElt := new(ResElement)
resElt.Res = res
res.StayDetail = append(res.StayDetail, resElt)
order := new(Order)
order.Res = res
orderList = append(orderList, order)
originalOrder := new(Order)
originalOrder.Res = new(Res)
*originalOrder.Res = *order.Res
//originalOrder.Res.StayDetail[0].Res.OtaBookID = "B123" //this will make all become "B123"
originalOrder.Res.OtaBookID = "B123"
orderList = append(orderList, originalOrder)
fmt.Println(orderList[0].Res.OtaBookID) //A123
fmt.Println(orderList[1].Res.OtaBookID) //B123
fmt.Println(orderList[0].Res.StayDetail[0].Res.OtaBookID) //A123
fmt.Println(orderList[1].Res.StayDetail[0].Res.OtaBookID) //A123, i want this become B123
}
永远记住,指针只是一个内存地址。如果地址值为0xffab67e1,指针的副本也将包含相同的0xffab67e1值,并有效地指向相同的对象。因此,您必须在新地址处故意分配新的内存空间,并复制内部值。对于任何包含指针的结构都必须这样做。我们称之为深度复制或克隆。我认为您只是滥用了示例中的指针。无论你在哪里,你都不需要它,因为我正在接管别人的工作。这三种类型在许多其他代码中使用谢谢你的回答,我很抱歉给你带来麻烦,因为我忽略了太多的信息,现在我在这三种类型中补充了更多的信息,并解释了为什么我有这三种类型,正如我在问题中补充的,这三种类型在我接管其他人的作品时已经存在。并且在许多其他代码中使用过,所以很难调整。
type Order struct {
*Res
Status int
}
type Res struct {
ResID int64
OtaBookID string
StayDetail []*ResElement
TotalCharge float64
CustFName string
CustLName string
CreateTime time.Time
}
type ResElement struct {
Res *Res
OtaEleID string
OtaRoomID string
RoomID int
Arrival time.Time
Depart time.Time
Charge float64
CreateTime time.Time
}
func main() {
var orderList []*Order
res := new(Res)
res.OtaBookID = "A123"
resElt := new(ResElement)
resElt.Res = res
res.StayDetail = append(res.StayDetail, resElt)
order := new(Order)
order.Res = res
orderList = append(orderList, order)
originalOrder := new(Order)
originalOrder.Res = new(Res)
// The following statement will copy the values in the memory space of order to the memory
// space of originalOrder, but take note that a pointer contains a memory address. Thus,
// following this statement originalOrder.Res.StayDetail will point to the same address
// as order.Res.StayDetail as slices are pointers...
*originalOrder.Res = *order.Res
// We now have to manually copy the slice to ensure it is different from the one in order.
// We must create a new slice to avoid overwriting the source.
originalOrder.Res.StayDetail := make([]*ResElement, len(order.Res.StayDetail))
// Further, this slice contains pointers so we must copy these as well to ensure they do not
// point to the ResElements of order.
for i, v := range order.Res.StayDetail {
re := new(ResElement)
// copy the values of the memory in v to the values in the memory of re
*re = *v
// set re.Res to point to originalOrder.Res as it currently point to order.Res
re.Res = originalOrder.Res
// Now we must place re in the slice of originalOrder as it currently points to an
// empty array of the correct size. Thus, we will not use append (which will grow
// the size), we will just set the index to the correct value. Thus:
originalOrder.StayDetail[i] = re
}
// The pointers and structures have now been properly set up, thus the following are equivalent:
// originalOrder.OtaBookID = "B123" - Res via embedding
// originalOrder.Res.OtaBookID = "B123" - Res directly
// originalOrder.Res.StayDetail[0].Res.OtaBookID = "B123" - Res via ResElement pointer Res
// They all point to the exact same memory space
originalOrder.Res.OtaBookID = "B123"
orderList = append(orderList, originalOrder)
fmt.Println(orderList[0].Res.OtaBookID) //A123
fmt.Println(orderList[1].Res.OtaBookID) //B123
fmt.Println(orderList[0].Res.StayDetail[0].Res.OtaBookID) //A123
fmt.Println(orderList[1].Res.StayDetail[0].Res.OtaBookID) //B123
}