Getting error [UIImage length]: unrecognized selector

Question

I got this error

2014-05-08 11:36:11.781 LtrRainOptic[1176:c07] * Terminating app due to uncaught exception NSInvalidArgumentException, reason: -[UIImage length]: unrecognized selector sent to instance 0x7af55c0'

 -(void)letterfall
{
   letterView.clipsToBounds = YES;
   image4 = [[UIImageView alloc]initWithFrame:CGRectMake(200, -80, 200, 200)];
   image4.image = [UIImage imageNamed:[sprtL objectAtIndex:0]];
   [letterView addSubview:image4];
   self->falling=[NSTimer scheduledTimerWithTimeInterval:0.015 target:self    selector:@selector(letterPosition) userInfo:nil repeats:YES];
}


-(void)setImagesInArray
{
    if (numLtr == 1)
{
       //if (r == 1) {   [self filltheLetterArray];}
        image4.image = [UIImage imageNamed:[oneletter objectAtIndex:r]];
       r++;
}

}

-(void)filltheLetterArray
{
   fillrequried = [self requiredArray];
   int rand;
    if (numLtr == 1)
   {
       rand = (0 + arc4random()%(1));
      [oneletter replaceObjectAtIndex:rand withObject:[sprtL objectAtIndex:sliderindex]];
      if (rand == 1) {    [oneletter replaceObjectAtIndex:0 withObject:[sprtL objectAtIndex:[self randomImage]]];}
      else           {    [oneletter replaceObjectAtIndex:1 withObject:[sprtL objectAtIndex:[self randomImage]]];}
}
    [self letterfall];
}


-(void)letterPosition
{
    if (numLtr == 1)
    {
        image4.frame = CGRectMake(image4.frame.origin.x, image4.frame.origin.y + 2, image4.frame.size.width, image4.frame.size.height);
    }
    if (image4.frame.origin.y >= 690) 
    {  
        [falling invalidate];
        falling = nil;
        [self filltheLetterArray];
    }
}

Answer 1

There's problem in your filltheLetterArray method, you're replacing objects in oneletter array, you're storing images (UIImages from randomImage method)directly into it, and this method crashing the app, setImagesInArray, this line image4.image = [UIImage imageNamed:[oneletter objectAtIndex:r]]; as you're assigning image file name (as NSString) but actually its containing UIImage objects.