digitalmars.D.learn - A couple questions about a simple project
- Andre Polykanine via Digitalmars-d-learn (29/29) Aug 17 2015 Hi everyone,
- John Colvin (12/43) Aug 17 2015 Check if args has changed length after calling getopt, if not
- Andre Polykanine via Digitalmars-d-learn (47/78) Aug 17 2015 Hello John,
- =?UTF-8?B?QWxpIMOHZWhyZWxp?= (25/46) Aug 17 2015 output(format("%s: validation passed!", f));
- FreeSlave (15/46) Aug 17 2015 1. getopt modifies args array leaving not processed arguments in
Hi everyone, I'm new to D (I'm learning it by reading the great online book by Ali Çehreli - thank you very much for it, sir!), and, more than that, programming is my hobby, so please bear with me if I'm asking stupid questions. I've made a toy project which is a small command-line XML files validator: https://github.com/Oire/dxv/ and I have a couple questions about it: 1. I'm using std.getopt but don't know how to make it display a help message if no options are present at all: D:\repos\git\dxv\dxv.exe (nothing happens but I would like it to show the help as with --help switch) 2. As you can see, I check whether the file to validate can be read. I tried both `try...catch` and `enforce` (current version: `string s = enforce(cast(string)std.file.read(f), "Unable to read file");` ), but this very exception for some reason can be caught only in `main()`. What am I missing? Thanks! -- With best regards from Ukraine, Andre Skype: Francophile Twitter: m_elensule; Facebook: menelion My blog: http://menelion.oire.org/
Aug 17 2015
On Monday, 17 August 2015 at 15:05:56 UTC, Andre Polykanine wrote:Hi everyone, I'm new to D (I'm learning it by reading the great online book by Ali Çehreli - thank you very much for it, sir!), and, more than that, programming is my hobby, so please bear with me if I'm asking stupid questions. I've made a toy project which is a small command-line XML files validator: https://github.com/Oire/dxv/ and I have a couple questions about it: 1. I'm using std.getopt but don't know how to make it display a help message if no options are present at all: D:\repos\git\dxv\dxv.exe (nothing happens but I would like it to show the help as with --help switch)Check if args has changed length after calling getopt, if not then it didn't find any options.2. As you can see, I check whether the file to validate can be read. I tried both `try...catch` and `enforce` (current version: `string s = enforce(cast(string)std.file.read(f), "Unable to read file");` ), but this very exception for some reason can be caught only in `main()`. What am I missing? Thanks!string s; try { s = cast(string)std.file.read(f); } catch (FileException e) { // do whatever you want. }
Aug 17 2015
Hello John,
Yes, but this doesn't work, either.
Now I have this (that was my first variant, btw):
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));
}
}
To catch the exception, I need to wrap the validate() call in
`try...catch` in `main()`. Why so?
Thanks!
--
With best regards from Ukraine,
Andre
Skype: Francophile
Twitter: m_elensule; Facebook: menelion
My blog: http://menelion.oire.org/
------------ Original message ------------
From: John Colvin via Digitalmars-d-learn <digitalmars-d-learn puremagic.com>
To: digitalmars-d-learn puremagic.com
Date created: , 6:17:38 PM
Subject: A couple questions about a simple project
On Monday, 17 August 2015 at 15:05:56 UTC, Andre Polykanine wrote:
Hi everyone,
I'm new to D (I'm learning it by reading the great online book
by Ali
Çehreli - thank you very much for it, sir!), and, more
than that,
programming is my hobby, so please bear with me if I'm asking
stupid
questions.
I've made a toy project which is a small command-line
XML files
validator:
https://github.com/Oire/dxv/
and I have a couple questions about it:
1. I'm using std.getopt but don't know how to make it display
a help
message if no options are present at all:
D:\repos\git\dxv\dxv.exe
(nothing happens but I would like it to show the help
as with
--help switch)
Check if args has changed length after calling getopt, if not
then it didn't find any options.
2. As you can see, I check whether the file to validate can be
read. I
tried both `try...catch` and `enforce` (current version:
`string s = enforce(cast(string)std.file.read(f), "Unable
to read
file");`
), but this very exception for some reason can be caught
only in
`main()`.
What am I missing?
Thanks!
string s;
try
{
s = cast(string)std.file.read(f);
}
catch (FileException e)
{
// do whatever you want.
}
Aug 17 2015
=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> 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 worksoutput(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
Aug 17 2015
On Monday, 17 August 2015 at 15:05:56 UTC, Andre Polykanine wrote:Hi everyone, I'm new to D (I'm learning it by reading the great online book by Ali Çehreli - thank you very much for it, sir!), and, more than that, programming is my hobby, so please bear with me if I'm asking stupid questions. I've made a toy project which is a small command-line XML files validator: https://github.com/Oire/dxv/ and I have a couple questions about it: 1. I'm using std.getopt but don't know how to make it display a help message if no options are present at all: D:\repos\git\dxv\dxv.exe (nothing happens but I would like it to show the help as with --help switch) 2. As you can see, I check whether the file to validate can be read. I tried both `try...catch` and `enforce` (current version: `string s = enforce(cast(string)std.file.read(f), "Unable to read file");` ), but this very exception for some reason can be caught only in `main()`. What am I missing? Thanks!1. getopt modifies args array leaving not processed arguments in it, i.e. name of the program and positional arguments (those without leading - or --). If there're no command line arguments given, args array will contain the only one element - the name of executable. Therefore you can check for args.length == 1 after processing by getopt. 2. catch can handle only exception of type specified in its argument and derived. std.file.read throws FileException on fail, while you catch only CheckException. To cover all cases you can catch any exception by using Exception type (it's the base class for all exception classes), or write two catch-statements in a row for both FileException and CheckException. You don't need enforce here, unless you want to check if std.file.read returns null slice.
Aug 17 2015