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Every time you change existing code, you break some other part of the system. You may not realize it, but you do. It may show up in the form of a broken unit test, but that presumes that a) said unit test exists, and b) it properly tests the aspect of the code you are changing. Sadly, more often than not, there is either no test to cover your change, or any test that does exist doesn't handle the case you are changing.
The dependency graph of your application can provide a lot of insight into how objects call each other. In a well designed application, this is probably mostly acyclic and no one node on the graph has more than a handful of edges coming off of it. The kinds of applications we talk about here, on the other hand, we have a name for their graphs: the Enterprise Dependency and the Big Ball of Yarn.
Thomas K introduces us to an entirely new iteration: The Big Ball of Mandelbrot
We often point to dates as one of the example data types which is so complicated that most developers can’t understand them. This is unfair, as pretty much every data type has weird quirks and edge cases which make for unexpected behaviors. Floating point rounding, integer overflows and underflows, various types of string representation…
But file-not-founds excepted, people have to understand Booleans, right?
"On my admittedly old and cheap phone, Google Maps seems to have confused the definition of the word 'trip'," writes Ivan.
In programming, sometimes the ordering of your data matters. And sometimes the ordering doesn’t matter and it can be completely random. And sometimes… well, El Dorko found a case where it apparently matters that it doesn’t matter:
DirectoryInfo di = new DirectoryInfo(directory);
FileInfo[] files = di.GetFiles();
DirectoryInfo[] subdirs = di.GetDirectories();
// shuffle subdirs to avoid problematic places
Random rnd = new Random();
for( int i = subdirs.Length - 1; i > 0; i-- )
{
int n = rnd.Next( i + 1 );
DirectoryInfo tmp = subdirs[i];
subdirs[i] = subdirs[n];
subdirs[n] = tmp;
}
foreach (DirectoryInfo dir in subdirs)
{
// process files in directory
}Have you ever secured something with a lock? The intent is that at some point in the future, you'll use the requisite key to regain access to it. Of course, the underlying assumption is that you actually have the key. How do you open a lock once you've lost the key? That's when you need to get creative. Lock picks. Bolt cutters. Blow torch. GAU-8...
In 2004, Ben S. went on a solo bicycle tour, and for reasons of weight, his only computer was a Handspring Visor Deluxe PDA running Palm OS. He had an external, folding keyboard that he would use to type his notes from each day of the trip. To keep these notes organized by day, he stored them in the Datebook (calendar) app as all-day events. The PDA would sync with a desktop computer using a Handspring-branded fork of the Palm Desktop software. The whole Datebook could then be exported as a text file from there. As such, Ben figured his notes were safe. After the trip ended, he bought a Windows PC that he had until 2010, but he never quite got around to exporting the text file. After he switched to using a Mac, he copied the files to the Mac and gave away the PC.
We talk a lot about the sort of wheels one shouldn’t reinvent. Loads of bad code stumbles down that path. Today, Mary sends us some code from their home-grown unit testing framework.
Mary doesn’t have much to say about whatever case of Not Invented Here Syndrome brought things to this point. It’s especially notable that this is Python, which comes, out of the box, with a perfectly serviceable unittest module built in. Apparently not serviceable enough for their team, however, as Burt, the Lead Developer, wrote his own.
Yasmin needed to fetch some data from a database for a report. Specifically, she needed to get all the order data. All of it. No matter how much there was.
The required query might be long running, but it wouldn’t be complicated. By policy, every query needed to be implemented as a stored procedure. Yasmin, being a smart prograammer, decided to check and see if anybody had already implemented a stored procedure which did what she needed. She found one called GetAllOrders. Perfect! She tested it in her report.