iOS NSComparisonresult issue - objective-c

Question

It raises an exception when I enter more than two characters in the searchfield. I use NSComparisonResult to show results on a UITableView:
- (void)filterContentForSearchText:(NSString*)searchText
{
for (mystring in self.array)
{
NSComparisonResult result = [mystring compare:searchText options:(NSCaseInsensitiveSearch)
range:NSMakeRange(0, [searchText length])];
if (result == NSOrderedSame)
{
NSUInteger index=[self.array indexOfObjectIdenticalTo:mystring];
NSUInteger maxindex = index + 50;
for (index ; (index < [self.array count] && index <= maxindex && index!= NSNotFound); index ++)
{
[self.filteredListContent addObject:[NSDictionary dictionaryWithObjectsAndKeys:[self.array objectAtIndex:index],#"english",[self.secondarray objectAtIndex:index],#"translated",nil]];
}
break;
}
}
The output shows:
-[UIDeviceWhiteColor compare:options:range:]: unrecognized selector sent to instance 0x5e4a5d0
2011-11-06 12:10:51.932 XXX[2583:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UIDeviceWhiteColor compare:options:range:]: unrecognized selector sent to instance 0x5e4a5d0'
What does UIDeviceWhiteColor in this case mean?
self.array = [[NSArray alloc] initWithArray:
[[NSString stringWithContentsOfFile:[[NSBundle mainBundle] pathForResource:#"first" ofType:#"txt"]
encoding:NSUTF8StringEncoding error:NULL] componentsSeparatedByString:#"\n"]];
self.secondarray = [[NSArray alloc] initWithArray:
[[NSString stringWithContentsOfFile:[[NSBundle mainBundle] pathForResource:#"second" ofType:#"txt"]
encoding:NSUTF8StringEncoding error:NULL] componentsSeparatedByString:#"\n"]];

Answer 1

That's because there is a UIDeviceWhiteColor somewhere in your self.array, which should be made of just NSStrings. How do you populate this array?

Answer 2

There's a UIDeviceWhiteColor object in self.array. You should also cast mystring as an NSString or whatever kind of object it is. If you'd cast it in UIDeviceWhiteColor then the compiler would give you a warning that UIDeviceWhiteColor does not respond to compare:options:range:.
for (NSString *mystring in self.array)
{
//some code
}