A couple questions about a simple project

[Ali Çehreli via Digitalmars-d-learn]

On 08/17/2015 10:08 AM, Andre Polykanine via Digitalmars-d-learn wrote:

 >                                  string s;
 >                                  try {
 >                                          s = 
cast(string)std.file.read(f);
 >                                          try {
 >                                                  check(s);
 >                                                  if (this.verbose) {
 > 
output(format("%s: validation passed!", f));
 >                                                  }
 >                                          } catch(CheckException e) {
 > // This is output when a file is invalid, that works
 > 
output(format("Failed to validate %s: %s", f, e.toString()));
 >                                          }
 >                                  } catch(Exception exc) {
 > //  And  that  isn't  output,  I  see  just  the  stacktrace as if the
 > exception was not caught at all
 >                                          output(format("Error reading 
%s: %s", f, exc.msg));
 >                                  }
 >                          }

Regardless of whether it is the best solution here, you can have 
multiple catch blocks for a single try:

try {
     // ...

} catch(CheckException e) {
     // ...

} catch(Exception exc) {
     // ...
}

 > To  catch  the  exception,  I  need  to  wrap  the  validate() call in
 > `try...catch` in `main()`. Why so?

The reason is you don't try to make use of the provided file name until 
validate() starts executing. If it's important that the program notify 
the user right away, then you can call std.file.exists() to make sure 
that the file is there. Still, it does not try to open so it can't know 
whether the file will be readable later.

The funny thing is, even though the upfront check sees a file as being 
present, it may disappear when it is being used or it may become unreadable.

A better solution may be to open the files first and then pass File 
objects to validate().

 > Thanks!

And thank you very much for the kind words! :)

Ali