Since *defer* "is the last thing to happen", I think this code is all right:
func something() (x int, err error) {
watch err != nil {
return
}
res, err = acquireResource()
defer func() {
if err == nil {
err = res.Close()
}
}()
err = abc1()
err = abc2()
err = abc3()
err = abc4()
}
Also, I'd like to make a general comment (not specific to this case). The
*watch* command doesn't seem (to me) a bad idea. And it could be used for
other purposes too (e.g. as the "watch expression" feature in debuggers or
for logging---yeah we don't really need it...).
For instance:
func calculations() {
x := 100.0
watch x < 0 {
fmt.Printf("hey, x is negative (%d)\n", x)
fmt.Printf("...no worries...\n")
}
x = compute(1,2,3)
x = compute(3,2,1)
x = compute(1,3,2)
}
It's of course NOT needed at all. Above, we can do the same thing in a
different (probably better) way.
In fact, *Go is perfect the way it is* and doesn't need any change at all!
Also, the mechanics (implementation) of *watch* may be "impossible", "too
hard", "confusing" or at least "inefficient"---I don't know (no idea...).
With an opportunity to work on the Go language implementation, I would
rather spend some time tweaking things to be faster...
Cheers!
Dorival
On Wednesday, September 6, 2017 at 1:11:36 AM UTC+10, eko...@gmail.com
wrote:
>
> I've been doing something like this for long chains where "handle error"
> is the same:
>
> func something() (x int, err error) {
> defer func() {
> if err != nil {
> // handle error
> }
> }()
> res, err = acquireResource()
> if err == nil {
> defer func() {
> if e := res.Close(); err == nil {
> err = e
> }
> }()
> err = abc1()
> }
> if err == nil {
> err = abc2()
> }
> if err == nil {
> err = abc3()
> }
> if err == nil {
> err = abc4()
> }
> }
>
> How would watch interact with defer?
>
> On Monday, September 4, 2017 at 8:27:20 PM UTC+2,
> marti...@programmfabrik.de wrote:
>>
>> Hi guys,
>>
>> at first I though I really like the idea of how Go deals with error
>> management and handling, but the more Go code I look at or try to program,
>> the more I get scared about checking errors every second line in every
>> given block of code.
>>
>> Take a look at this example here from "Build Web Application with Golang":
>>
>> // insert
>> stmt, err := db.Prepare("INSERT INTO userinfo(username, departname, created)
>> values(?,?,?)")
>> if err != nil {
>> // handle error
>> }
>> res, err := stmt.Exec("astaxie", "研发部门", "2012-12-09")
>> if err != nil {
>> // handle error
>> }
>> id, err := res.LastInsertId()
>> if err != nil {
>> // handle error
>> }
>> fmt.Println(id)
>> // update
>> stmt, err = db.Prepare("update userinfo set username=? where uid=?")
>> if err != nil {
>> // handle error
>> }
>> res, err = stmt.Exec("astaxieupdate", id)
>> if err != nil {
>> // handle error
>> }
>> affect, err := res.RowsAffected()
>> if err != nil {
>> // handle error
>> }
>>
>>
>> Seriously? And yes, I have read
>> https://blog.golang.org/errors-are-values...
>>
>> The best case reduction I found is:
>>
>> ...
>> res, err = stmt.Exec("astaxieupdate", id)
>> checkError(err)
>> ...
>>
>> Still, I need this after each line of calling a function which may return
>> an error.
>>
>> I bet this is not pleasant to do in larger code bases and it also takes
>> away focus from what is actually happening.
>>
>> 50-80% of all lines of code in my example deal with error handling?
>>
>> This is not good. Seriously.
>>
>> And don't get me wrong, there is a lot of things I really like, love and
>> adore about Go, but catching errors needs an improved syntax!
>>
>> And I am not proposing try...catch here.
>>
>> How about introducing a new piece of syntax
>>
>> "watch if .... "
>>
>> which tells the compiler to watch out for changes in a given SimpleStmt
>>
>> The same code as above would look like this:
>>
>> var err Error
>>
>> watch if err != nil {
>> // handle error(s)
>> }
>>
>> // insert
>> stmt, err := db.Prepare("INSERT INTO userinfo(username, departname,
>> created) values(?,?,?)")
>> res, err := stmt.Exec("astaxie", "研发部门", "2012-12-09")
>> id, err := res.LastInsertId()
>> fmt.Println(id)
>>
>> // update
>> stmt, err = db.Prepare("update userinfo set username=? where uid=?")
>> res, err = stmt.Exec("astaxieupdate", id)
>> affect, err := res.RowsAffected()
>>
>>
>> - The "watch if" would be executed after each assignment of any of
>> the variables used in SimpleStmt of the statement.
>> - Multiple "watch if" would be executed in order or appearance
>> - The "watch if" could be used like "defer..." inside functions
>> - The "watch if" would work in its full scope of the watched variables
>>
>> I am not a language expert, so may be there is a saner way of expression
>> what I want to achieve.
>>
>> But bottom line is, there should by an easier to read and write way to
>> deal with errors in Go.
>>
>>
>> Martin
>>
>>
>>
>>
>>
>>
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