[asterisk-users] AEL switch & case

[Antony Stone]

Replying to list this time...

On Wednesday 31 August 2022 at 12:47:13, asterisk at phreaknet.org wrote:

> On 8/31/2022 6:32 AM, Antony Stone wrote:
> > Hi.
> > 
> > I think I've discovered a bug in either the implementation or the
> > documentation of the AEL switch command.
> > 
> > https://wiki.asterisk.org/wiki/display/AST/AEL+Conditionals gives an
> > example of using switch, and states at the bottom:
> > 
> > "Neither the switch nor case values are wrapped in $[ ]; they can be
> > constants, or ${var} type references only."
> > 
> > However, I've run into a problem, which can be demonstrated by the simple
> > context:
> > 
> > context SwitchTest {
> >    s => {
> >      Set(FortyTwo=42);
> >      Set(SixByNine=54);
> >      switch(${SixByNine}) {
> >        case 123:
> >          NoOp(123);
> >          break;
> >        case ${FortyTwo}:
> >          NoOp(${FortyTwo});
> >          break;
> >      }
> >    }
> > }

> > Am I misundertanding "they can be constants, or ${var} type references
> > only."?
> 
> I don't think this is a bug. ${FortyTwo} is not defined when the AEL
> dialplan is transpiled into dialplan. It only gets set at runtime.

Agreed, however that is surely a perfectly reasonable "${var} type reference"?

> This might work if you made FortyTwo a global variable, which would be
> available when this gets parsed.

Quite possibly, but I would expect switch() to work in the same way as 
multiple if() statements:

switch(${a}) {
  case ${b}: NoOp(${b} matches); break;
  case ${c}: NoOp(${c} matches); break;
// etc....
}

should be equivalent to:

if(${a}=${b}) NoOp(${b} matches);
if(${a}=${c}) NoOp(${c} matches);
// etc....

The latter works perfectly well, no matter when ${b} and ${c} are assigned 
their values.

I've adjusted my dialplan to use multiple if()s, but I still thik that either 
the implementation or the documentation of switch is incorrect.


Antony.

-- 
I bought a book on memory techniques, but I've forgotten where I put it.

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