NSString *extension = @"txt";
NSFileManager *fileManager = [NSFileManager defaultManager];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];

NSArray *contents = [fileManager contentsOfDirectoryAtPath:documentsDirectory error:NULL];
NSEnumerator *e = [contents objectEnumerator];
NSString *filename;
while ((filename = [e nextObject])) {

if ([[filename pathExtension] isEqualToString:extension]||[[filename pathExtension] isEqualToString:@"db"]) {

[fileManager removeItemAtPath:[documentsDirectory stringByAppendingPathComponent:filename] error:NULL];
}
}

针对后缀删除文件的方法