英文:
How to make method return value if panic happen and processed in defer func(){...}() in golang
问题
我的功能必须无论成功还是发生恐慌都返回一个字符串。
func getDBStoreStatus() string {
var replyMessage string
defer func() string {
if err := recover(); err != nil {
replyMessage = "发生错误。"
}
return replyMessage
}()
// 将行存储到数据库中
db, err := sql.Open("mysql", "user1:password@/databaseName?charset=utf8")
newMessage, err := db.Prepare("INSERT .............")
res, err := newMessage.Exec(...........)
if err != nil {
panic(err)
}
replyMessage = "OK"
return replyMessage
}
如果恐慌在 defer 部分被处理，我该如何返回一个字符串？你可以看到 defer 部分的 return 语句无法正常工作。
英文:
My function must return a string whatever success or panic.
func getDBStoreStatus() string{
var replyMessage string
defer func() string{
if err := recover(); err != nil {
replyMessage = "Error happend."
}
return replyMessage
}()
//do something to store row into DB
db, err := sql.Open("mysql", "user1:password@/databaseName?charset=utf8")
newMessage, err := db.Prepare("INSERT .............
res, err := newMessage.Exec(...........
if err != nil {
panic(err)
}
replyMessage = "OK"
return replyMessage
}
How can I return a string, if the panic processed by defer section?
You can see the return statement in defer section doesn't work properly.
答案1
得分: 1
给你的返回参数命名，然后你可以在defer方法中设置它：
func getDBStoreStatus() (replyMessage string) {
defer func(){
if err := recover(); err != nil {
replyMessage = "Error happend."
}
}()
//do something to store row into DB
db, err := sql.Open("mysql", "user1:password@/databaseName?charset=utf8")
newMessage, err := db.Prepare("INSERT .............")
res, err := newMessage.Exec(...........)
if err != nil {
panic(err)
}
replyMessage = "OK"
return replyMessage
}
参考Go博客上的Defer, Panic and Recover：
- 延迟函数可以读取和赋值给返回函数的命名返回值。
在这个例子中，延迟函数在包围函数返回后递增返回值i。因此，这个函数返回2：
func c() (i int) { defer func() { i++ }() return 1 }
不过我真的看不出有什么意义。你可以直接这样做：
if err != nil {
return "Error happend."
}
而不是使用panic(err)。
英文:
Name your return parameter, then you can set it in the defer method:
func getDBStoreStatus() (replyMessage string) {
defer func(){
if err := recover(); err != nil {
replyMessage = "Error happend."
}
}()
//do something to store row into DB
db, err := sql.Open("mysql", "user1:password@/databaseName?charset=utf8")
newMessage, err := db.Prepare("INSERT .............
res, err := newMessage.Exec(...........
if err != nil {
panic(err)
}
replyMessage = "OK"
return replyMessage
}
See the Go Blog post on Defer, Panic and Recover:
> 3. Deferred functions may read and assign to the returning function's named return values.
>
> In this example, a deferred function increments the return value i
> after the surrounding function returns. Thus, this function returns 2:
>
> func c() (i int) {
> defer func() { i++ }()
> return 1
> }
I don't really see the point, though. You could just do:
if err != nil {
return "Error happend."
}
instead of panic(err).
1: http://blog.golang.org/defer-panic-and-recover
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