Throw an Exception?

canalrun · May 13, 2012

Hello,
I would like to throw an exception as a means of breaking out of a series of loops as a check for something totally unexpected. I could not find an example or if this is even possible.

Here is some "dream" code. Is something like this possible in B4A? What is the correct syntax?

B4X:

Try
.....
  .....
    .....
      If (x < 0) Then Throw
    .....
  .....
.....
Catch
  Log("This will never work.")
End Try

Thanks,
Barry.

corwin42 · May 14, 2012

I haven't tried it but the Threading library has an ExceptionEx object which can throw exceptions.

kickaha · May 14, 2012

Why not seperate the block of loops into a function, and then to break out of them all you need to do is return. You can use a return value to check if it returned due to an error.

Erel · May 14, 2012

You can also do something like:

B4X:

If x < 0 Then ThrowError


Sub ThrowError
 Dim i As Int
 i = "sdf"
End Sub

canalrun · May 14, 2012

Thanks.
Using ExceptionEx is the solution. I found a quick example embedded in code intended as a threading example – very helpful.

I have a bunch of nested loops within a subroutine. If I get an interim result that is negative, this physically makes no sense. I have to abort and exit the subroutine. This is actually a case when Goto's are useful, but using an Exception and Throw is a more structured solution.

Thanks,
Barry.

mc73 · May 14, 2012

Perhaps, using a flag would do it? For example,

B4X:

do while flagError=false and flagFinalResult=false
if x<0 then
flagerror=true
else
'continue
flagFinalResult=true
end if
loop
if flagerrror=true then
return
else
'continue
end if

I don't know, just a thought.

Throw an Exception?

canalrun

Well-Known Member

corwin42

Expert

kickaha

Well-Known Member

Erel

B4X founder

canalrun

Well-Known Member

mc73

Well-Known Member

Throw an Exception?

canalrun

Well-Known Member

corwin42

Expert

kickaha

Well-Known Member

Erel

B4X founder

canalrun

Well-Known Member

mc73

Well-Known Member

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