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    <p><strong>Logging</strong></p> <p>Vala has some fairly robust logging facilities built in. You can use <code>debug()</code>, <code>message()</code>, <code>warning()</code>, <code>error()</code>, and <code>critical()</code> as shortcuts for the slightly more complex <a href="http://valadoc.org/#!api=glib-2.0/GLib.log" rel="noreferrer"><code>log()</code></a> function. All are included in the base (automatically included) <a href="http://valadoc.org/#!wiki=glib-2.0/index" rel="noreferrer"><code>GLib</code> namespace</a>.</p> <p>If you want to redirect log output or send different types of messages to different destinations, everything you need is in the <a href="http://valadoc.org/#!api=glib-2.0/GLib.Log" rel="noreferrer"><code>GLib.Log</code> namespace</a>. You might want to read the <a href="http://developer.gnome.org/glib/stable/glib-Message-Logging.html" rel="noreferrer">glib docs on logging</a> for what's going on behind the scenes there.</p> <p><strong>Defensive Programming</strong></p> <p>Vala also includes support for assertions and contracts. The short version: <code>assert()</code> and <code>assert_not_reached()</code> for assertions, and <code>requires()</code> and <code>ensures()</code> in method signatures for contracts. See the tutorial section on <a href="http://live.gnome.org/Vala/Tutorial#Assertions_and_Contract_Programming" rel="noreferrer">Assertions and Contract Programming</a> for more info.</p> <p><strong>Error Handling</strong></p> <p>Vala's error handling is a little odd: similar-looking to exceptions, but not quite the same. The tutorial section on <a href="http://live.gnome.org/Vala/Tutorial#Error_Handling" rel="noreferrer">Error Handling</a> covers the basics pretty well, and again it might be helpful to read the <a href="http://developer.gnome.org/glib/stable/glib-Error-Reporting.html" rel="noreferrer">glib docs on errors</a> to get a more advanced understanding of what's going on behind the scenes. As far as I know, there is no way to get a stack trace out of Vala errors -- just a type and a message.</p> <p><strong>Best Practices</strong></p> <p>In terms of best practices, I think Vala is similar enough to Java or C# that the practices you already know can be applied in a general sense. I suggest playing around with these features to get a feel for how the specifics look in Vala. Good luck!</p>
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    1. CODoes Vala support custom messages for contract violations? Or is it going to give a cryptic default error message? I'm trying to find a good way to throw errors and the default "Error Handling"/"Contractual Programming" sections of the Vala tutorial don't seem to describe anything truly useful.
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    2. COIt looks like contracts are compiled into calls to g_return_if_fail(), which doesn't support any custom error message. And you're right that the error message it shows from the generated C code isn't the most helpful. If you want custom errors with your own messages to get thrown, Vala doesn't offer any syntactic sugar for you -- you'll just have to do it the old fashioned way with if and throw.
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