How to retrieve where an error happens

SimJ

I get an error message that I wrote myself in a method, but I can't figure out in which centext it happens.

Example :

void aMethod() {
 if(problem){print("Error");}
}

The method aMethod is used in a lots of different contexts in my sketch. How can I modify my error message so I get something like the stack trace of an error ?

KevinWorkman

You can use exceptions for this.

If you want to pass an error up the stack:

if(problem){
   throw new Exception("Error");
}

If you just want to print a stack trace:

if(problem){
  new Exception().printStackTrace();
}

Shameless self-promotion: I wrote a tutorial on Exceptions available here.

kfrajer

What id your definition for problem? You get access to the stack when an error is thrown. However, how to merge your approach with:

try {
    .....
} 
catch (IOException e) {
  e.printStackTrace();
}

More info is needed.

Kf

Chrisir

first idea

you can make a different println statement in every place that aMethod() is called

println ("I am line number 93 calling aMethod()");
aMethod(); 

second idea

OR you can pass an ID (or a String) to aMethod():

void aMethod(int ID) {
     if(problem) { 
        print("Error: " + ID);
    }
 }

SimJ

@KevinWorkman the first solution gives me an Unhandled exception type Exception. The second doesn't print anything but looks to me like what I'm looking for.

@kfrajer the true situation is :

Real divide(Real A, Real B) { // divide A by B
  if(B.isZero()){print("Error");}
  else{...}
}

For a homemade class Real

@Chrisir I'll use this as a last resort if I can't find something easier to handle

KevinWorkman

That is what I would expect the first solution to do. You need to handle the exception. Please read the link on exceptions I posted above.

The second solution should print a stack trace to your console, unless you're immediately exiting or something. Please post a MCVE showing exactly what you tried.

SimJ

Problem solved, new Exception().printStackTrace(); did it ! I realized that I wrote the same error message in another line in the same method, and it was this other one that was written in the console. Thanks !