UIImage gives nil - objective-c

Question

I'm quite new to iOS development. My app gets a file over a network, writes it as image.png and later on reads and displays the image. However, the display part is not working as my UIImage object is always set to nil (on the iOS simulator). I've tried implementing other answers from stackoverflow, but no luck.
Here's my code to save the file:
//inside utility class for model
NSFileHandle * handle = nil;
//For first packet of new file request
if(CountFileParts == 1)
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *appFile = [documentsDirectory stringByAppendingPathComponent:#"image.png"];
NSLog(#"%#",appFile);
handle = [NSFileHandle fileHandleForWritingAtPath:appFile];
if(handle == nil)
{
[[NSFileManager defaultManager] createFileAtPath:appFile contents:nil attributes:nil];
handle = [NSFileHandle fileHandleForWritingAtPath:appFile];
}
}
//For other incoming packets of the same request
else
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *appFile = [documentsDirectory stringByAppendingPathComponent:#"image.png"];
//NSLog(#"%#",appFile);
handle = [NSFileHandle fileHandleForUpdatingAtPath:appFile];
[handle seekToEndOfFile];
//NSLog(#"Writing continue in new file");
}
if(handle == nil)
NSLog(#"handle nil");
NSData * data = [str dataUsingEncoding:NSUTF8StringEncoding];
[handle writeData:data];
[handle closeFile];
if(index != -1 && index!= NSNotFound)
{
NSLog(#"Inside Bool");
self.isPlotReady = YES;//kvo in view-controller as shown below
self.isPlotReady = NO;
}
Here's my code to load the image file:
-(void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
if([keyPath isEqualToString:#"isPlotReady"])
{
self.isReady = [[change objectForKey:NSKeyValueChangeNewKey] boolValue];
[self updateUI];
}
}
-(void) updateUI
{
if(self.isReady)
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
[self lsOwnDirectory:documentsDirectory];
NSString *appFile = [documentsDirectory stringByAppendingPathComponent:#"image.png"];
//NSLog(#"%#",appFile);
UIImage *img = [UIImage imageWithContentsOfFile:appFile];
if(img == nil)
NSLog(#"Couldn't find image");
else
{
UIImageView *imageView = [[UIImageView alloc] initWithImage:img] ;
[self.view addSubview:imageView];
}
}
}
//Prints Directory contents of input directory
- (void) lsOwnDirectory:(NSString *) currentpath {
NSError * error = [[NSError alloc] init];
NSFileManager *filemgr;
filemgr = [[NSFileManager alloc] init];
//currentpath = [filemgr currentDirectoryPath];
NSLog(#"Current Directory Path : %#",currentpath);
NSArray * files = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:currentpath error: &error];
for(NSString * file in files){
NSLog(#"%#", file);
}
}
It alway's prints "Couldn't find image" corresponding to the if statement, but I've seen the file is still there (lsOwnDirectory prints directory contents). Maybe I'm doing something basic wrong here. Thanks in advance.