Assigning the returning error to an underscore
I've been reading some Golang code from github.com/lib/pq which provides drivers for interacting with a postgres database.
Among the code I came across this:
go func() {
select {
case <-done:
_ = cn.cancel()
finished <- struct{}{}
case <-finished:
}
}()
The cancel function looks like:
func (cn *conn) cancel() error
As far as I can tell, the underscore isn't being used as a static assertion about a type (and therefore the compiler doesn't evaluate any side effects as far as I can see (as in this example)) and it isn't a second parameter whereby the author may want to discard it.
In summary: Why assign the result of the cancel function (the error) to an underscore?
go error-handling pq
asked Dec 30 '18 at 9:12
RambatinoRambatino
1,93711437
add a comment |
I've been reading some Golang code from github.com/lib/pq which provides drivers for interacting with a postgres database.
Among the code I came across this:
go func() {
select {
case <-done:
_ = cn.cancel()
finished <- struct{}{}
case <-finished:
}
}()
The cancel function looks like:
func (cn *conn) cancel() error
As far as I can tell, the underscore isn't being used as a static assertion about a type (and therefore the compiler doesn't evaluate any side effects as far as I can see (as in this example)) and it isn't a second parameter whereby the author may want to discard it.
In summary: Why assign the result of the cancel function (the error) to an underscore?
go error-handling pq
asked Dec 30 '18 at 9:12
RambatinoRambatino
1,93711437
2
Apart from being explicit about discarding the error there is no difference between_ = cancel()andcancel().
– mkopriva
Dec 30 '18 at 9:56
add a comment |
I've been reading some Golang code from github.com/lib/pq which provides drivers for interacting with a postgres database.
Among the code I came across this:
go func() {
select {
case <-done:
_ = cn.cancel()
finished <- struct{}{}
case <-finished:
}
}()
The cancel function looks like:
func (cn *conn) cancel() error
As far as I can tell, the underscore isn't being used as a static assertion about a type (and therefore the compiler doesn't evaluate any side effects as far as I can see (as in this example)) and it isn't a second parameter whereby the author may want to discard it.
In summary: Why assign the result of the cancel function (the error) to an underscore?
go error-handling pq
asked Dec 30 '18 at 9:12
RambatinoRambatino
1,93711437
I've been reading some Golang code from github.com/lib/pq which provides drivers for interacting with a postgres database.
Among the code I came across this:
go func() {
select {
case <-done:
_ = cn.cancel()
finished <- struct{}{}
case <-finished:
}
}()
The cancel function looks like:
func (cn *conn) cancel() error
As far as I can tell, the underscore isn't being used as a static assertion about a type (and therefore the compiler doesn't evaluate any side effects as far as I can see (as in this example)) and it isn't a second parameter whereby the author may want to discard it.
In summary: Why assign the result of the cancel function (the error) to an underscore?
go error-handling pq
go error-handling pq
asked Dec 30 '18 at 9:12
RambatinoRambatino
1,93711437
asked Dec 30 '18 at 9:12
RambatinoRambatino
1,93711437
asked Dec 30 '18 at 9:12
RambatinoRambatino
1,93711437
asked Dec 30 '18 at 9:12
RambatinoRambatino
1,93711437
asked Dec 30 '18 at 9:12
RambatinoRambatino
1,93711437
1,93711437
2
Apart from being explicit about discarding the error there is no difference between_ = cancel()andcancel().
– mkopriva
Dec 30 '18 at 9:56
add a comment |
2
Apart from being explicit about discarding the error there is no difference between_ = cancel()andcancel().
– mkopriva
Dec 30 '18 at 9:56
2
2
Apart from being explicit about discarding the error there is no difference between
_ = cancel() and cancel().– mkopriva
Dec 30 '18 at 9:56
Apart from being explicit about discarding the error there is no difference between
_ = cancel() and cancel().– mkopriva
Dec 30 '18 at 9:56
add a comment |
2 Answers
2
active
oldest
votes
Code must be correct. To be sure that code is correct, code must be readable.
The First Rule of Go: Check for errors.
func (cn *conn) cancel() error
If I write
cn.cancel()
did I forget to check for errors or did I decide to discard the error value?
However, if I write
_ = cn.cancel()
I did not forget to check for errors and I did decide to discard the error value.
The Go Programming Language Specification
Blank identifier
The blank identifier is represented by the underscore character _. It
serves as an anonymous placeholder instead of a regular (non-blank)
identifier and has special meaning in declarations, as an operand, and
in assignments.
Assignments
The blank identifier provides a way to ignore right-hand side values
in an assignment:
answered Dec 30 '18 at 11:07
peterSOpeterSO
93.9k14160175
add a comment |
The blank identifier “_” is a special anonymous identifier. When used in an assignment, like this case, it provides a way to explicitly ignore right-hand side values. So, the developer has decided to ignore/discard the error returned from this method call.
A few reasons why they may have done this (based on a quick glance at the method call and context, my guess is 3 or 4):
- The method call is guaranteed to succeed in this context.
- The error is already handled sufficiently within the method call; no reason to handle it again.
- The error doesn’t matter (eg the relevant process is going to end anyway and the outcome will be the same as if the method call has succeeded without error).
- The developer was in a hurry to get something working, ignored the error to save time, then failed to come back and handle the error.
answered Dec 30 '18 at 9:55
blobdonblobdon
57237
Please, can you comment on your downvote so I can attempt to make this better, or learn from my errors?
– blobdon
Dec 30 '18 at 11:17
Seems very informative to me @blobdon, thanks!
– Rambatino
Jan 5 at 7:38
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
Code must be correct. To be sure that code is correct, code must be readable.
The First Rule of Go: Check for errors.
func (cn *conn) cancel() error
If I write
cn.cancel()
did I forget to check for errors or did I decide to discard the error value?
However, if I write
_ = cn.cancel()
I did not forget to check for errors and I did decide to discard the error value.
The Go Programming Language Specification
Blank identifier
The blank identifier is represented by the underscore character _. It
serves as an anonymous placeholder instead of a regular (non-blank)
identifier and has special meaning in declarations, as an operand, and
in assignments.
Assignments
The blank identifier provides a way to ignore right-hand side values
in an assignment:
answered Dec 30 '18 at 11:07
peterSOpeterSO
93.9k14160175
add a comment |
Code must be correct. To be sure that code is correct, code must be readable.
The First Rule of Go: Check for errors.
func (cn *conn) cancel() error
If I write
cn.cancel()
did I forget to check for errors or did I decide to discard the error value?
However, if I write
_ = cn.cancel()
I did not forget to check for errors and I did decide to discard the error value.
The Go Programming Language Specification
Blank identifier
The blank identifier is represented by the underscore character _. It
serves as an anonymous placeholder instead of a regular (non-blank)
identifier and has special meaning in declarations, as an operand, and
in assignments.
Assignments
The blank identifier provides a way to ignore right-hand side values
in an assignment:
answered Dec 30 '18 at 11:07
peterSOpeterSO
93.9k14160175
add a comment |
Code must be correct. To be sure that code is correct, code must be readable.
The First Rule of Go: Check for errors.
func (cn *conn) cancel() error
If I write
cn.cancel()
did I forget to check for errors or did I decide to discard the error value?
However, if I write
_ = cn.cancel()
I did not forget to check for errors and I did decide to discard the error value.
The Go Programming Language Specification
Blank identifier
The blank identifier is represented by the underscore character _. It
serves as an anonymous placeholder instead of a regular (non-blank)
identifier and has special meaning in declarations, as an operand, and
in assignments.
Assignments
The blank identifier provides a way to ignore right-hand side values
in an assignment:
answered Dec 30 '18 at 11:07
peterSOpeterSO
93.9k14160175
Code must be correct. To be sure that code is correct, code must be readable.
The First Rule of Go: Check for errors.
func (cn *conn) cancel() error
If I write
cn.cancel()
did I forget to check for errors or did I decide to discard the error value?
However, if I write
_ = cn.cancel()
I did not forget to check for errors and I did decide to discard the error value.
The Go Programming Language Specification
Blank identifier
The blank identifier is represented by the underscore character _. It
serves as an anonymous placeholder instead of a regular (non-blank)
identifier and has special meaning in declarations, as an operand, and
in assignments.
Assignments
The blank identifier provides a way to ignore right-hand side values
in an assignment:
answered Dec 30 '18 at 11:07
peterSOpeterSO
93.9k14160175
edited Dec 30 '18 at 12:50
answered Dec 30 '18 at 11:07
peterSOpeterSO
93.9k14160175
answered Dec 30 '18 at 11:07
peterSOpeterSO
93.9k14160175
answered Dec 30 '18 at 11:07
peterSOpeterSO
93.9k14160175
93.9k14160175
add a comment |
add a comment |
The blank identifier “_” is a special anonymous identifier. When used in an assignment, like this case, it provides a way to explicitly ignore right-hand side values. So, the developer has decided to ignore/discard the error returned from this method call.
A few reasons why they may have done this (based on a quick glance at the method call and context, my guess is 3 or 4):
- The method call is guaranteed to succeed in this context.
- The error is already handled sufficiently within the method call; no reason to handle it again.
- The error doesn’t matter (eg the relevant process is going to end anyway and the outcome will be the same as if the method call has succeeded without error).
- The developer was in a hurry to get something working, ignored the error to save time, then failed to come back and handle the error.
answered Dec 30 '18 at 9:55
blobdonblobdon
57237
Please, can you comment on your downvote so I can attempt to make this better, or learn from my errors?
– blobdon
Dec 30 '18 at 11:17
Seems very informative to me @blobdon, thanks!
– Rambatino
Jan 5 at 7:38
add a comment |
The blank identifier “_” is a special anonymous identifier. When used in an assignment, like this case, it provides a way to explicitly ignore right-hand side values. So, the developer has decided to ignore/discard the error returned from this method call.
A few reasons why they may have done this (based on a quick glance at the method call and context, my guess is 3 or 4):
- The method call is guaranteed to succeed in this context.
- The error is already handled sufficiently within the method call; no reason to handle it again.
- The error doesn’t matter (eg the relevant process is going to end anyway and the outcome will be the same as if the method call has succeeded without error).
- The developer was in a hurry to get something working, ignored the error to save time, then failed to come back and handle the error.
answered Dec 30 '18 at 9:55
blobdonblobdon
57237
Please, can you comment on your downvote so I can attempt to make this better, or learn from my errors?
– blobdon
Dec 30 '18 at 11:17
Seems very informative to me @blobdon, thanks!
– Rambatino
Jan 5 at 7:38
add a comment |
The blank identifier “_” is a special anonymous identifier. When used in an assignment, like this case, it provides a way to explicitly ignore right-hand side values. So, the developer has decided to ignore/discard the error returned from this method call.
A few reasons why they may have done this (based on a quick glance at the method call and context, my guess is 3 or 4):
- The method call is guaranteed to succeed in this context.
- The error is already handled sufficiently within the method call; no reason to handle it again.
- The error doesn’t matter (eg the relevant process is going to end anyway and the outcome will be the same as if the method call has succeeded without error).
- The developer was in a hurry to get something working, ignored the error to save time, then failed to come back and handle the error.
answered Dec 30 '18 at 9:55
blobdonblobdon
57237
The blank identifier “_” is a special anonymous identifier. When used in an assignment, like this case, it provides a way to explicitly ignore right-hand side values. So, the developer has decided to ignore/discard the error returned from this method call.
A few reasons why they may have done this (based on a quick glance at the method call and context, my guess is 3 or 4):
- The method call is guaranteed to succeed in this context.
- The error is already handled sufficiently within the method call; no reason to handle it again.
- The error doesn’t matter (eg the relevant process is going to end anyway and the outcome will be the same as if the method call has succeeded without error).
- The developer was in a hurry to get something working, ignored the error to save time, then failed to come back and handle the error.
answered Dec 30 '18 at 9:55
blobdonblobdon
57237
edited Dec 30 '18 at 11:40
answered Dec 30 '18 at 9:55
blobdonblobdon
57237
answered Dec 30 '18 at 9:55
blobdonblobdon
57237
answered Dec 30 '18 at 9:55
blobdonblobdon
57237
57237
Please, can you comment on your downvote so I can attempt to make this better, or learn from my errors?
– blobdon
Dec 30 '18 at 11:17
Seems very informative to me @blobdon, thanks!
– Rambatino
Jan 5 at 7:38
add a comment |
Please, can you comment on your downvote so I can attempt to make this better, or learn from my errors?
– blobdon
Dec 30 '18 at 11:17
Seems very informative to me @blobdon, thanks!
– Rambatino
Jan 5 at 7:38
Please, can you comment on your downvote so I can attempt to make this better, or learn from my errors?
– blobdon
Dec 30 '18 at 11:17
Please, can you comment on your downvote so I can attempt to make this better, or learn from my errors?
– blobdon
Dec 30 '18 at 11:17
Seems very informative to me @blobdon, thanks!
– Rambatino
Jan 5 at 7:38
Seems very informative to me @blobdon, thanks!
– Rambatino
Jan 5 at 7:38
add a comment |
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2
Apart from being explicit about discarding the error there is no difference between
_ = cancel()andcancel().– mkopriva
Dec 30 '18 at 9:56