英文:
Function that is returning struct or error
问题
我有一个类似这样的方法：
var eventNotDetected = errors.New("未检测到事件")
type VoucherUsageEvent struct {
M models.M
}
func detectVoucherUsageEvent(_ uint64, changeset changelog.Changeset) (VoucherUsageEvent, error) {
var event VoucherUsageEvent
if changeset.GetHeader().Table != db.TABLE_NAME {
return event, eventNotDetected
}
switch changeset.(type) {
case changelog.InsertChangeset, changelog.UpdateChangeset:
m, err := models.Map(changeset)
if err != nil {
return event, err
}
return VoucherUsageEvent{m}, nil
default:
return event, eventNotDetected
}
}
这个方法的思路是根据输入来决定是否返回对象实例。如果无法返回对象实例，函数应该指示无法返回的原因（映射过程中发生错误，或者对象未找到）。
当函数不返回实例时，返回的签名有点奇怪，例如：
return event, eventNotDetected
return event, err
基本上，我只是使用event，因为我不能只返回nil。
或者在这种情况下，更好的方法是返回一个引用，这样我可以将返回情况更改为：
return nil, eventNotDetected
return nil, err
英文:
I have method that looks like this:
var eventNotDetected = errors.New("Event not detected")
type VoucherUsageEvent struct {
M models.M
}
func detectVoucherUsageEvent(_ uint64, changeset changelog.Changeset) (VoucherUsageEvent, error) {
var event VoucherUsageEvent
if changeset.GetHeader().Table != db.TABLE_NAME {
return event, eventNotDetected
}
switch changeset.(type) {
case changelog.InsertChangeset, changelog.UpdateChangeset:
m, err := models.Map(changeset)
if err != nil {
return event, err
}
return VoucherUsageEvent{m}, nil
default:
return event, eventNotDetected
}
}
The idea is that it can return an object instance or not, depending on the input. If the object instance can't be returned, the function should indicate why it could not be returned (error occurred during mapping, or just not found)
The return signature is a bit weird when the function doesn't return the instance, for example:
return event, eventNotDetected
return event, err
Basically I just use event because I can't return just nil.
Or is the better way to just return a reference in this case, so I could change the return cases to:
return nil, eventNotDetected
return nil, err
答案1
得分: 0
是的，你可以将输出参数定义为指针*VoucherUsageEvent。
func detectVoucherUsageEvent(_ uint64, changeset changelog.Changeset) (*VoucherUsageEvent, error)
可以返回引用或nil。
return &VoucherUsageEvent{m}, nil
或者
return &event, eventNotDetected
或者
return nil, err
英文:
Yes you can, define the out parameter as pointer *VoucherUsageEvent.
func detectVoucherUsageEvent(_ uint64, changeset changelog.Changeset) (*VoucherUsageEvent, error)
Return as reference or nil.
return &VoucherUsageEvent{m}, nil
OR
return &event, eventNotDetected
OR
return nil, err
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论