Hi Daniel,
currently I would be +/- 0 on this.
Thoughts:
1. I feel I have written this before, but I myself do not encounter the
situation where I would need to return the result of a method call
only if it meets certain conditions when programming (maybe you can
give some real life code where you encounter this on a regular basis ?).
2. If I have more than one return, it typcially is an early out, which
depends on the method's input parameters, not on the result of
another method call.
3. Since I do a lot of logging / log debugging, I typically assign the
return value to a variable, so I can debug-log it before the one
return of the method.
4. In fact I have had to refactor code written by other people from
multi-return methods to single return, to be able to track down bugs.
So overall I am not sure one should enable people to make it easier to
write non-single-return methods ;-)
Purely syntax wise I would prefer
return?
for the simple case,
and
return <something> if <condition>
for the more complex one*.
I find
return(<condition) <something>
confusing on what is actually returned.
Cheers,
mg
*Though I wonder if people would not then expect this if-postfix-syntax
to also work for e.g. assignments and method calls...
On 26/07/2020 16:15, Daniel Sun wrote:
Hi Mario,
I think you have got the point of the proposal ;-)
If we prefer the verbose but clear syntax, I think we could introduce `_`
to represent the return value for concise shape:
```
return callB() if (_ != null && _ > 10)
// The following code is like lambda expression, which is a bit more verbose
return callB() if (result -> result != null && result > 10)
```
Show the `_` usage in your example:
```
def doSomething(int a) {
return callB() if (a > 6 && _ > 10)
return callC() if (a > 5 && _ > 20)
return callD() if (a > 4 && _ > 30)
}
```
```
// optional parentheses
def doSomething(int a) {
return callB() if a > 6 && _ > 10
return callC() if a > 5 && _ > 20
return callD() if a > 4 && _ > 30
}
```
```
// one more example
def doSomething(int a) {
return callB() if a > 6 && _ > 10
return callC() + callD() if a > 5 && _ > 50
}
```
BTW, the parentheses behind `if` could be optional.
Cheers,
Daniel Sun
On 2020/07/26 11:29:39, Mario Garcia <mario.g...@gmail.com> wrote:
Hi all:
Very interesting topic.
The first idea sprang to mind was the PMD rule in Java saying you should
have more than one exit point in your methods (
https://pmd.github.io/latest/pmd_rules_java_codestyle.html#onlyonereturn).
But the reality is that sometimes (more often than not) we are forced to
break that rule. In fact sometimes we could even argue that breaking that
rule makes the code clearer (e.g
https://medium.com/ncr-edinburgh/early-exit-c86d5f0698ba)
Although my initial reaction was to be against the proposal, however after
doing some coding, I've found that neither elvis nor ternary operators
makes it easier nor clearer. Here's why I think so. Taking Daniel's example:
```
def m() {
def a = callA()
if (null != a) return a
def b = callB()
if (b > 10) return b
def c = callC()
if (null != c && c < 10) return c
LOGGER.debug('the default value will be returned')
return defaultValue
}
```
The shortest elvis operator approach I could think of was:
```
def m2() {
return callA()
?: callB().with { it > 10 ? it : null }
?: callC().with { null != it && it <10 ? it : null }
}
```
which to be honest, is ugly to read, whereas Daniel's proposal is just:
```
def m() {
return? callA()
return(r -> r > 10) callB()
return(r -> null != r && r < 10) callC()
return defaultValue
}
```
Once said that, I would say this conditional return could be useful only
when there are more than two exit points, otherwise ternary or elvis
operators may be good enough.
So, bottom line, I kinda agree to add conditional return, but I'm not sure
about the final syntax:
```
return(r -> r > 10) callB()
return callB() [r -> r > 10]
return callB() if (r -> r > 10)
```
Between the three I the one that I like the most is the third one:
```
return callB() if (r -> r > 10)
```
You can read it in plain english as "return this if this condition
happens".
Apart from Daniel's use case, using this option could open the
possibility to use, not only a closure or lambda expression, but also a
plain expression. A nice side effect could be that something like the
following code:
```
def doSomething(int a) {
return callB() if a > 6
return callC() if a > 5
return callD() if a > 4
}
```
turns out to be a shorter (and in my opinion nicest) way of switch case
(when you want every branch to return something):
```
def doSomething(int a) {
switch (a) {
case { it > 6 }: return callB()
case { it > 5 }: return callC()
case { it > 4 }: return callD()
}
}
```
Well, bottom line, I'm +1 Daniel's proposal because I've seen some cases
where this conditional return could make the code clearer.
Cheers
Mario
El sáb., 25 jul. 2020 a las 23:55, Paolo Di Tommaso (<
paolo.ditomm...@gmail.com>) escribió:
It's not much easier a conditional expression (or even the elvis
operator)?
```
def m() {
def r = callSomeMethod()
return r != null ? r : theDefaultResult
}
```
On Sat, Jul 25, 2020 at 8:56 PM Daniel Sun <sun...@apache.org> wrote:
Hi all,
We always have to check the returning value, if it match some
condition, return it. How about simplifying it? Let's see an example:
```
def m() {
def r = callSomeMethod()
if (null != r) return r
return theDefaultResult
}
```
How about simplifying the above code as follows:
```
def m() {
return? callSomeMethod()
return theDefaultResult
}
```
Futhermore, we could make the conditional return more general:
```
def m() {
return(r -> r != null) callSomeMethod() // we could do more checking,
e.g. r > 10
return theDefaultResult
}
```
Any thoughts?
Cheers,
Daniel Sun
