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El Presidente · Aug 14, 2001, 05:21 AM

I have a little function that I am going to use in a file browsing application that takes an array and returns a filtered array. The array contains the names of files in a certain directory. The filter removes known invisibles from that array. Another thing I need to remove are items that begin with a dot ( "." ).

Here is the function:
<BLOCKQUOTE>code:<HR><pre>
NSArray *RemoveHiddenFiles(NSArray *dirArray)
{
NSArray *hiddenFiles = [[NSArray alloc] initWithObjects:@"bin", @"Cleanup At Startup", @"cores", @"Desktop DB", @"Desktop DF", @"dev", @"etc", @"mach", @"mach.sym", @"mach_kernel", @"private", @"sbin", @"Temporary Items", @"TheFindByContentFolder", @"TheVolumeSettingsFolder", @"tmp", @"Trash", @"usr", @"var", nil];
NSMutableArray *filteredFiles = [[NSMutableArray alloc] initWithArray:dirArray];
int num1, num2;
for (num2=0; num2<[filteredFiles count]; num2++)
{
if ([[[filteredFiles objectAtIndex:num2] substringWithRange:NSMakeRange(0,1)] isEqualToString:@"."])
{
[filteredFiles removeObjectAtIndex:num2];
}
}
for (num1=0; num1<[hiddenFiles count]; num1++)
{
[filteredFiles removeObject:[hiddenFiles objectAtIndex:num1]];
}
return (NSArray *)filteredFiles;
}
[/code]

Yeah, there are probably some memory leaks, but I will get to those later. The real problem is that when I try to remove files starting with a dot, it only removes .DS_Store and .Trashes.

In my home directory I have a lot more than that (.xinitrc, .gimp, .dillo, etc.). In the root directory there are still .vol and .hidden.

I don't know why the filter won't remove those files, I think there might be something wrong with the for loop, but that is just a guess.

Any help would be greatly appreciated.

lindberg · Aug 14, 2001, 01:51 PM

When you remove an item from the array, all of its objects above it shift down one slot, and so your index is now incorrect. You should not increment num2 if you remove an object, or start num2 at count-1 and decrement each iteration instead, stopping when num < 0. Or, more cleanly, don't create a copy first but instead only add "validated" objects to the filtered array. Generally, be very careful when removing items from an array you're iterating over -- it's very easy to make mistakes. Removing objects from an array when you're using an NSEnumerator to do the iteration is illegal for this reason.

<BLOCKQUOTE>code:<HR><pre>
NSArray *RemoveHiddenFiles(NSArray *dirArray)
{
static NSArray *hiddenFiles = nil;
NSMutableArray *filteredFiles = [NSMutableArray arrayWithCapacity:[dirArray count]];
int num;

if (hiddenFiles == nil)
hiddenFiles = [[NSArray alloc] initWithObjects:@"bin", @"Cleanup At Startup", @"cores", @"Desktop DB", @"Desktop DF", @"dev", @"etc", @"mach", @"mach.sym", @"mach_kernel", @"private", @"sbin", @"Temporary Items", @"TheFindByContentFolder", @"TheVolumeSettingsFolder", @"tmp", @"Trash", @"usr", @"var", nil];

for (num=0; num<[dirArray count]; num++)
{
NSString *name = [dirArray objectAtIndex:num];

if (![name hasPrefix:@"."] && ![hiddenFiles containsObject:name])
[filteredFiles addObject:name];
}

return filteredFiles;
}
[/code]

Also as a FYI, the ".hidden" file in a directory contains a list of files that don't show up in Finder. That's actually what Finder uses to filter with for files that don't start with '.'.

Also, your second loop in your original code could have been replaced with [filteredFiles removeObjectsInArray:hiddenFiles] though I did it a different way above. Just for future reference :-)

El Presidente · Aug 14, 2001, 08:14 PM

Wow, thanks a lot!

I actually tried using the removeobjectsinarray, but it didn't work, probably for the reason you stated.