Hi, maybe I dont understand safeinvoke operator correctly but following code throws exception.
Code>
using xml
class SafeInvokeTest
{
static Void main()
{
element := XElem("test")
echo("$element element.text = $element.text")
test := element.text?.val.toInt
echo("$test")
}
}
When I change element.text?.val.toInt to element.text?.val?.toInt variable test is null as expected. This is I dont understand, because XElem.text signature is XText? and XText.val signature is Str, and I think that when I dont have nullable val slot I can use normall call.
Is it bug or I just dont understand it well :]
Thx
Ivos
Yuri StrotFri 14 Dec 2012
This is actually by design, see this discussion: #1461.
And I believe since v1.0.61 there should be compile check for such chaining calls:
Currently I am using fantom-1.0.63 and when I compile there is no error. What I do not understand is that, why call did not ended at first null value and insted of it compiler passes Str with value "null" and try to convert it to Int with exception.
brianFri 14 Dec 2012
If you look at your code, it is really looks like this:
temp := element.text?.val
test := temp.toInt
Since temp is null, the non-safe call to toInt fails with NPE. What you need is:
test := element.text?.val?.toInt
As ystrot said, we need to fix the compiler to report that as an error
katoxFri 14 Dec 2012
@bedla Safe invoke is not really a global operation (working within a statement) but a normal operator.
Ok, no problem for me. But I think, that docs should be updated to capture this "corner case" (Groovy's explanation, URL you provided, makes more sance for me than Fantom docs).
bedla Fri 14 Dec 2012
Hi, maybe I dont understand safeinvoke operator correctly but following code throws exception.
Code>
using xml class SafeInvokeTest { static Void main() { element := XElem("test") echo("$element element.text = $element.text") test := element.text?.val.toInt echo("$test") } }Console output>
When I change
element.text?.val.toInttoelement.text?.val?.toIntvariabletestisnullas expected. This is I dont understand, becauseXElem.textsignature isXText?andXText.valsignature isStr, and I think that when I dont have nullablevalslot I can use normall call.Is it bug or I just dont understand it well :]
Thx
Ivos
Yuri Strot Fri 14 Dec 2012
This is actually by design, see this discussion: #1461.
And I believe since v1.0.61 there should be compile check for such chaining calls:
fansh> "".index("a")?.toStr.toInt ERROR(26): Non-null safe call chained after null safe callbedla Fri 14 Dec 2012
Currently I am using fantom-1.0.63 and when I compile there is no error. What I do not understand is that, why call did not ended at first
nullvalue and insted of it compiler passesStrwith value"null"and try to convert it toIntwith exception.brian Fri 14 Dec 2012
If you look at your code, it is really looks like this:
Since temp is null, the non-safe call to toInt fails with NPE. What you need is:
As ystrot said, we need to fix the compiler to report that as an error
katox Fri 14 Dec 2012
@bedla Safe invoke is not really a global operation (working within a statement) but a normal operator.
This is the same situation as in Groovy (originating safe-invoke operator as well as elvis operator, I guess). See for example http://www.nearinfinity.com/blogs/jeff_kunkle/groovys_safe_navigation_operat.html
bedla Sat 15 Dec 2012
Ok, no problem for me. But I think, that docs should be updated to capture this "corner case" (Groovy's explanation, URL you provided, makes more sance for me than Fantom docs).