Different types of closure syntax in swift - which one is correct?
up vote
3
down vote
favorite
I'm pretty curious which one of these syntax statements is (more) correct.
Playground happily compiles both cases.
Method 1
// copied from SO and this appears clear to me
UIView.animate(
withDuration: 3.0,
animations: {
},
completion: { (Bool) in
// completion code
}
)
Method 2
UIView.animate(
withDuration: 3.0,
animations: {
// code
}) {(Bool) in
// code when finished?
// argument label completion missing?
}
Why rounded brackets in 2nd method are closed before last argument stated? Or is that another implementation of UIView.animation?
ios swift closures swift3 completionhandler
asked Sep 22 '16 at 15:21
GiorgioE
129110
add a comment |
up vote
3
down vote
favorite
I'm pretty curious which one of these syntax statements is (more) correct.
Playground happily compiles both cases.
Method 1
// copied from SO and this appears clear to me
UIView.animate(
withDuration: 3.0,
animations: {
},
completion: { (Bool) in
// completion code
}
)
Method 2
UIView.animate(
withDuration: 3.0,
animations: {
// code
}) {(Bool) in
// code when finished?
// argument label completion missing?
}
Why rounded brackets in 2nd method are closed before last argument stated? Or is that another implementation of UIView.animation?
ios swift closures swift3 completionhandler
asked Sep 22 '16 at 15:21
GiorgioE
129110
add a comment |
up vote
3
down vote
favorite
up vote
3
down vote
favorite
I'm pretty curious which one of these syntax statements is (more) correct.
Playground happily compiles both cases.
Method 1
// copied from SO and this appears clear to me
UIView.animate(
withDuration: 3.0,
animations: {
},
completion: { (Bool) in
// completion code
}
)
Method 2
UIView.animate(
withDuration: 3.0,
animations: {
// code
}) {(Bool) in
// code when finished?
// argument label completion missing?
}
Why rounded brackets in 2nd method are closed before last argument stated? Or is that another implementation of UIView.animation?
ios swift closures swift3 completionhandler
asked Sep 22 '16 at 15:21
GiorgioE
129110
I'm pretty curious which one of these syntax statements is (more) correct.
Playground happily compiles both cases.
Method 1
// copied from SO and this appears clear to me
UIView.animate(
withDuration: 3.0,
animations: {
},
completion: { (Bool) in
// completion code
}
)
Method 2
UIView.animate(
withDuration: 3.0,
animations: {
// code
}) {(Bool) in
// code when finished?
// argument label completion missing?
}
Why rounded brackets in 2nd method are closed before last argument stated? Or is that another implementation of UIView.animation?
ios swift closures swift3 completionhandler
ios swift closures swift3 completionhandler
asked Sep 22 '16 at 15:21
GiorgioE
129110
asked Sep 22 '16 at 15:21
GiorgioE
129110
asked Sep 22 '16 at 15:21
GiorgioE
129110
asked Sep 22 '16 at 15:21
GiorgioE
129110
asked Sep 22 '16 at 15:21
GiorgioE
129110
129110
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
up vote
4
down vote
accepted
The difference between both methods is following:
Method 1: Regular closure
Method 2: Trailing closure.
Last closure parameter in the signature of a function can be written in shorter syntax. If the second parameter would be completion, and animations parameter would be the last, the trailing closure would apply to animations etc.
So it has to stand as the last (or the only) closure parameter.
If you miss a completion label, you are free to type it like this:
UIView.animate(withDuration: 3.0, animations: {
}) {(completion: Bool) in
}
For completion of your question as well: It is the same implementation of an identical function, but a different syntax.
answered Sep 22 '16 at 15:25
pedrouan
9,17124060
1
Was going to say that, but you stated it nicely. The advantage of using the trailing closure is that it often results in cleaner looking code.
– picciano
Sep 22 '16 at 15:27
Well after I took a look again, it appeared to me cleaner looking too :) Thank you.
– GiorgioE
Sep 22 '16 at 15:40
add a comment |
up vote
6
down vote
Both of them are correct.
It is the usual closure syntax in a function call.
It represents a Trailing closure.
If you need to pass a closure expression to a function as the
function’s final argument and the closure expression is long, it can
be useful to write it as a trailing closure instead. A trailing
closure is written after the function call’s parentheses, even though
it is still an argument to the function. When you use the trailing
closure syntax, you don’t write the argument label for the closure as
part of the function call.
You can read more about trailing closures from https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Closures.html
answered Sep 22 '16 at 15:29
PGDev
6,33721145
1
Thank you, so we shouldn't write arg. label within trailing closure? Or just it is not needed?
– GiorgioE
Sep 22 '16 at 15:39
2
There is no scope for writing argument label with trailing closure. "completion:" need not be written. The body of the trailing closure is written outside the method calling brackets i.e UIView.animate(...){trailing closure body}
– PGDev
Sep 22 '16 at 15:56
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
up vote
4
down vote
accepted
The difference between both methods is following:
Method 1: Regular closure
Method 2: Trailing closure.
Last closure parameter in the signature of a function can be written in shorter syntax. If the second parameter would be completion, and animations parameter would be the last, the trailing closure would apply to animations etc.
So it has to stand as the last (or the only) closure parameter.
If you miss a completion label, you are free to type it like this:
UIView.animate(withDuration: 3.0, animations: {
}) {(completion: Bool) in
}
For completion of your question as well: It is the same implementation of an identical function, but a different syntax.
answered Sep 22 '16 at 15:25
pedrouan
9,17124060
1
Was going to say that, but you stated it nicely. The advantage of using the trailing closure is that it often results in cleaner looking code.
– picciano
Sep 22 '16 at 15:27
Well after I took a look again, it appeared to me cleaner looking too :) Thank you.
– GiorgioE
Sep 22 '16 at 15:40
add a comment |
up vote
4
down vote
accepted
The difference between both methods is following:
Method 1: Regular closure
Method 2: Trailing closure.
Last closure parameter in the signature of a function can be written in shorter syntax. If the second parameter would be completion, and animations parameter would be the last, the trailing closure would apply to animations etc.
So it has to stand as the last (or the only) closure parameter.
If you miss a completion label, you are free to type it like this:
UIView.animate(withDuration: 3.0, animations: {
}) {(completion: Bool) in
}
For completion of your question as well: It is the same implementation of an identical function, but a different syntax.
answered Sep 22 '16 at 15:25
pedrouan
9,17124060
1
Was going to say that, but you stated it nicely. The advantage of using the trailing closure is that it often results in cleaner looking code.
– picciano
Sep 22 '16 at 15:27
Well after I took a look again, it appeared to me cleaner looking too :) Thank you.
– GiorgioE
Sep 22 '16 at 15:40
add a comment |
up vote
4
down vote
accepted
up vote
4
down vote
accepted
The difference between both methods is following:
Method 1: Regular closure
Method 2: Trailing closure.
Last closure parameter in the signature of a function can be written in shorter syntax. If the second parameter would be completion, and animations parameter would be the last, the trailing closure would apply to animations etc.
So it has to stand as the last (or the only) closure parameter.
If you miss a completion label, you are free to type it like this:
UIView.animate(withDuration: 3.0, animations: {
}) {(completion: Bool) in
}
For completion of your question as well: It is the same implementation of an identical function, but a different syntax.
answered Sep 22 '16 at 15:25
pedrouan
9,17124060
The difference between both methods is following:
Method 1: Regular closure
Method 2: Trailing closure.
Last closure parameter in the signature of a function can be written in shorter syntax. If the second parameter would be completion, and animations parameter would be the last, the trailing closure would apply to animations etc.
So it has to stand as the last (or the only) closure parameter.
If you miss a completion label, you are free to type it like this:
UIView.animate(withDuration: 3.0, animations: {
}) {(completion: Bool) in
}
For completion of your question as well: It is the same implementation of an identical function, but a different syntax.
answered Sep 22 '16 at 15:25
pedrouan
9,17124060
edited Sep 22 '16 at 15:37
answered Sep 22 '16 at 15:25
pedrouan
9,17124060
answered Sep 22 '16 at 15:25
pedrouan
9,17124060
answered Sep 22 '16 at 15:25
pedrouan
9,17124060
9,17124060
1
Was going to say that, but you stated it nicely. The advantage of using the trailing closure is that it often results in cleaner looking code.
– picciano
Sep 22 '16 at 15:27
Well after I took a look again, it appeared to me cleaner looking too :) Thank you.
– GiorgioE
Sep 22 '16 at 15:40
add a comment |
1
Was going to say that, but you stated it nicely. The advantage of using the trailing closure is that it often results in cleaner looking code.
– picciano
Sep 22 '16 at 15:27
Well after I took a look again, it appeared to me cleaner looking too :) Thank you.
– GiorgioE
Sep 22 '16 at 15:40
1
1
Was going to say that, but you stated it nicely. The advantage of using the trailing closure is that it often results in cleaner looking code.
– picciano
Sep 22 '16 at 15:27
Was going to say that, but you stated it nicely. The advantage of using the trailing closure is that it often results in cleaner looking code.
– picciano
Sep 22 '16 at 15:27
Well after I took a look again, it appeared to me cleaner looking too :) Thank you.
– GiorgioE
Sep 22 '16 at 15:40
Well after I took a look again, it appeared to me cleaner looking too :) Thank you.
– GiorgioE
Sep 22 '16 at 15:40
add a comment |
up vote
6
down vote
Both of them are correct.
It is the usual closure syntax in a function call.
It represents a Trailing closure.
If you need to pass a closure expression to a function as the
function’s final argument and the closure expression is long, it can
be useful to write it as a trailing closure instead. A trailing
closure is written after the function call’s parentheses, even though
it is still an argument to the function. When you use the trailing
closure syntax, you don’t write the argument label for the closure as
part of the function call.
You can read more about trailing closures from https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Closures.html
answered Sep 22 '16 at 15:29
PGDev
6,33721145
1
Thank you, so we shouldn't write arg. label within trailing closure? Or just it is not needed?
– GiorgioE
Sep 22 '16 at 15:39
2
There is no scope for writing argument label with trailing closure. "completion:" need not be written. The body of the trailing closure is written outside the method calling brackets i.e UIView.animate(...){trailing closure body}
– PGDev
Sep 22 '16 at 15:56
add a comment |
up vote
6
down vote
Both of them are correct.
It is the usual closure syntax in a function call.
It represents a Trailing closure.
If you need to pass a closure expression to a function as the
function’s final argument and the closure expression is long, it can
be useful to write it as a trailing closure instead. A trailing
closure is written after the function call’s parentheses, even though
it is still an argument to the function. When you use the trailing
closure syntax, you don’t write the argument label for the closure as
part of the function call.
You can read more about trailing closures from https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Closures.html
answered Sep 22 '16 at 15:29
PGDev
6,33721145
1
Thank you, so we shouldn't write arg. label within trailing closure? Or just it is not needed?
– GiorgioE
Sep 22 '16 at 15:39
2
There is no scope for writing argument label with trailing closure. "completion:" need not be written. The body of the trailing closure is written outside the method calling brackets i.e UIView.animate(...){trailing closure body}
– PGDev
Sep 22 '16 at 15:56
add a comment |
up vote
6
down vote
up vote
6
down vote
Both of them are correct.
It is the usual closure syntax in a function call.
It represents a Trailing closure.
If you need to pass a closure expression to a function as the
function’s final argument and the closure expression is long, it can
be useful to write it as a trailing closure instead. A trailing
closure is written after the function call’s parentheses, even though
it is still an argument to the function. When you use the trailing
closure syntax, you don’t write the argument label for the closure as
part of the function call.
You can read more about trailing closures from https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Closures.html
answered Sep 22 '16 at 15:29
PGDev
6,33721145
Both of them are correct.
It is the usual closure syntax in a function call.
It represents a Trailing closure.
If you need to pass a closure expression to a function as the
function’s final argument and the closure expression is long, it can
be useful to write it as a trailing closure instead. A trailing
closure is written after the function call’s parentheses, even though
it is still an argument to the function. When you use the trailing
closure syntax, you don’t write the argument label for the closure as
part of the function call.
You can read more about trailing closures from https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Closures.html
answered Sep 22 '16 at 15:29
PGDev
6,33721145
answered Sep 22 '16 at 15:29
PGDev
6,33721145
answered Sep 22 '16 at 15:29
PGDev
6,33721145
answered Sep 22 '16 at 15:29
PGDev
6,33721145
6,33721145
1
Thank you, so we shouldn't write arg. label within trailing closure? Or just it is not needed?
– GiorgioE
Sep 22 '16 at 15:39
2
There is no scope for writing argument label with trailing closure. "completion:" need not be written. The body of the trailing closure is written outside the method calling brackets i.e UIView.animate(...){trailing closure body}
– PGDev
Sep 22 '16 at 15:56
add a comment |
1
Thank you, so we shouldn't write arg. label within trailing closure? Or just it is not needed?
– GiorgioE
Sep 22 '16 at 15:39
2
There is no scope for writing argument label with trailing closure. "completion:" need not be written. The body of the trailing closure is written outside the method calling brackets i.e UIView.animate(...){trailing closure body}
– PGDev
Sep 22 '16 at 15:56
1
1
Thank you, so we shouldn't write arg. label within trailing closure? Or just it is not needed?
– GiorgioE
Sep 22 '16 at 15:39
Thank you, so we shouldn't write arg. label within trailing closure? Or just it is not needed?
– GiorgioE
Sep 22 '16 at 15:39
2
2
There is no scope for writing argument label with trailing closure. "completion:" need not be written. The body of the trailing closure is written outside the method calling brackets i.e UIView.animate(...){trailing closure body}
– PGDev
Sep 22 '16 at 15:56
There is no scope for writing argument label with trailing closure. "completion:" need not be written. The body of the trailing closure is written outside the method calling brackets i.e UIView.animate(...){trailing closure body}
– PGDev
Sep 22 '16 at 15:56
add a comment |
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