Change UIButton image to another one objective C - iphone

Question

I want to change an image on my UIButton when a user presses on it. The image has transparency effects (it is a .png that shows only an edge). The problem is that when the button is tapped, all works fine (other functions connected to it), but the app overwrites the 2 different images one over the second! When the button is pressed I want to show the second image, and remove the first (that becomes unnecessary). PS: I don't want to use array of images. Here the code for the button:
UIButton *overlayButton = [UIButton buttonWithType:UIButtonTypeCustom];
[overlayButton setImage:[UIImage imageNamed:#"image1.png"] forState:UIControlStateNormal];
[overlayButton setFrame:CGRectMake(20, 382, 120, 60)];
[overlayButton addTarget:self action:#selector(scanButtonPressed) forControlEvents:UIControlEventTouchUpInside]; //just graphics
[overlayButton addTarget:self action:#selector(buttonshapeClicked:) forControlEvents:UIControlEventTouchUpInside]; //just to set a variable i++ for my cycle
[overlayButton addTarget:self action:#selector(changeshape:) forControlEvents:UIControlEventTouchUpInside]; //function that changes another shape
[[self view] addSubview:overlayButton];
my simple cycle
- (void)buttonshapeClicked:(id)sender{
shape++;
if (shape == 4) {
shape = 1;
}}
here the main function that allows to change a primary shape on the screen
-(void) changeshape:(id)sender {
if (shape==1 && people==2) {
//bottone forma
UIButton *overlayButton = [UIButton buttonWithType:UIButtonTypeCustom];
[overlayButton setImage:[UIImage imageNamed:#"passaquadrato.png"] forState:UIControlStateNormal];
[overlayButton setFrame:CGRectMake(20, 382, 120, 60)];
[overlayButton addTarget:self action:#selector(scanButtonPressed) forControlEvents:UIControlEventTouchUpInside];
[overlayButton addTarget:self action:#selector(buttonshapeClicked:) forControlEvents:UIControlEventTouchUpInside];
[overlayButton addTarget:self action:#selector(changeshape:) forControlEvents:UIControlEventTouchUpInside];
[[self view] addSubview:overlayButton];
//bottone people
UIButton *overlayButtonp = [UIButton buttonWithType:UIButtonTypeCustom];
[overlayButtonp setImage:[UIImage imageNamed:#"passatre.png"] forState:UIControlStateNormal];
[overlayButtonp setFrame:CGRectMake(180, 382, 120, 60)];
[overlayButtonp addTarget:self action:#selector(scanButtonPressed) forControlEvents:UIControlEventTouchUpInside];
[[self view] addSubview:overlayButtonp];
UIImageView *overlayImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:#"circle2.png"]];
[overlayImageView setFrame:CGRectMake(20, 88, 280, 280)];
[[self view] addSubview:overlayImageView];
}
else if (shape==2 && people==2) {
//bottone forma
UIButton *overlayButton = [UIButton buttonWithType:UIButtonTypeCustom];
[overlayButton setImage:[UIImage imageNamed:#"passarettangolo.png"] forState:UIControlStateNormal];
[overlayButton setFrame:CGRectMake(20, 382, 120, 60)];
[overlayButton addTarget:self action:#selector(scanButtonPressed) forControlEvents:UIControlEventTouchUpInside];
[overlayButton addTarget:self action:#selector(buttonshapeClicked:) forControlEvents:UIControlEventTouchUpInside];
[overlayButton addTarget:self action:#selector(changeshape:) forControlEvents:UIControlEventTouchUpInside];
[[self view] addSubview:overlayButton];
//bottone people
UIButton *overlayButtonp = [UIButton buttonWithType:UIButtonTypeCustom];
[overlayButtonp setImage:[UIImage imageNamed:#"passatre.png"] forState:UIControlStateNormal];
[overlayButtonp setFrame:CGRectMake(180, 382, 120, 60)];
[overlayButtonp addTarget:self action:#selector(scanButtonPressed) forControlEvents:UIControlEventTouchUpInside];
[[self view] addSubview:overlayButtonp];
UIImageView *overlayImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:#"square2.png"]];
[overlayImageView setFrame:CGRectMake(20, 88, 280, 280)];
[[self view] addSubview:overlayImageView];
}}
I want to have the same button but with a different image to show

Answer 1

It doesn't look like you are ever removing the previous buttons.
Also, you don't have to create new buttons - you can simply store a reference to the button, and change the image, and change the action target (by removing the old ones before adding the new ones).

Answer 2

I've solved for a few of cycle with removing all from the view with:
for (int i = 0; i < [[self.view subviews] count]; i++ ) {
[[[self.view subviews] objectAtIndex:i] removeFromSuperview];
}
The problem now is to reinitialize the cycle because, when my variable goes to 4 I want that it becomes 1. I do it with:
- (void)buttonshapeClicked:(id)sender{shape++;
if (shape == 4) {
shape = 1;
}}
But after the number 4, I've the same problem of overview that I've had before!