QUIT argument not allowed

Akshat Vora 23 January 2020

Debugging, ObjectScript, Tips & Tricks, Caché, InterSystems IRIS

   try{
        ....
        ....
        ....

        Set tSC = method_invocation()

        If $$$ISERR(tSC) {
            Quit tSC
        }

        ....
        ....
        ....

}

On compiling the above, I get an error saying "QUIT argument not allowed : 'tSC' ".

When I replace Quit tSC with Return tSC, it compiles
On replacing Quit tSC with Quit $$$OK, I get the error: QUIT argument not allowed : '1'
On replacing Quit tSC with Quit, it compiles
A 'Quit tSC' statement outside of the try-catch block does not cause a compile-time error.

The reason this happens is because a 'Quit' inside a try-catch block causes control to be passed to the code immediately outside the try catch block instead of quitting the function and returning a value.

Sharing this here because it took me a while to realize what was happening (and although something related is briefly mentioned in the try-catch docs, I could only find it after I realized that the problem was related to try-catch)

Reply by Vasiliy Bondar 23 January 2020

try {

Set tSC = method_invocation()

If $$$ISERR(tSC) {

THROW tSC

}

} catch err {

+ 1 0

Reply by Jorge De La Garza 27 January 2020

Assuming that tSC is a %Library.Status, I don't think this will work the way you intend it to. The argument to a THROW has to be an oref to a class that extends %Exception.AbstractException:

https://docs.intersystems.com/irislatest/csp/docbook/DocBook.UI.Page.cls?KEY=RCOS_cthrow
If you have a %Status that you need to throw as an exception, you can use $$$ThrowOnError or $$$ThrowStatus, both defined in %occStatus.inc. They both call ##class(%Exception.StatusException).ThrowIfInterrupt(), but $$$ThrowOnError only does so if the status is an error, so it's slightly more efficient if you haven't checked the status yet.

0 0

Reply by Chris Eslinger 26 January 2020

Try {

$$$ThrowOnError(method_invocation()) {

} Catch ex {

$$$LOGSTATUS(ex.AsStatus())

Reply by Vitaliy Serdtsev 24 January 2020

It should be noted that this applies not only to the try/catch block, but also to other blocks, for example:

f i=1:1:2 {
  q 1 ; runtime error, but the line is highlighted
}

do {
  q 2 ; compilation error
}while(0)

while 0 {
  q 3 ; compilation error
}

Reply by Evgeny Shvarov 24 January 2020

This is what @Timothy Leavitt was talking about in his recent article.

+ 2 0

Reply by Alexander Woodhead 24 January 2020

Suggest use "Return" keyword instead of "Quit"

For example:

Class Test.ReturnOfTheTry [ Abstract ]
{

ClassMethod GetReturn(state = 0)
    {
    try {
      if state=1 return "In Try"
      set x=3/0
    } catch {
      if state=2 return "In Catch"
}
quit "At Methods End"
}

// Usage example

Write ##class(Test.ReturnOfTheTry).GetReturn(1)
In Try
Write ##class(Test.ReturnOfTheTry).GetReturn(2)
In Catch
Write ##class(Test.ReturnOfTheTry).GetReturn()
At Methods End

Reply by Ian Minshall 27 January 2020

Its a very common coding issue. I achieve what you are trying to do by this construct

Method DoStuff() As %Status
{
set tSC = $$$OK

do {

set tSC = method_invocation1()
quit:$$$ISERR(tSC)

set tSC = method_invocation2()
quit:$$$ISERR(tSC)

} while 0
quit tSC
}

This enables you to exit at the first issue with the relevant status.
The do while loop is just there to act as a 'container' for the code so you can jump out of it with a quit with no arguments, it can be replaced with a try catch block.

QUIT argument not allowed

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