UIButton problems - ios

Question

So I have been trying to get help with this from other users, but we can never get anywhere, my syntax and code looks good but no matter what I can not get rid of "undecared identifier" error when trying to call my button's method. Im starting to think it is a issue of global/vs not global. Here is my code and my errors
UIButton *add = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[add addTarget:self
action:#selector(aMethod:)forControlEvents:UIControlEventTouchDown];
[add setTitle:#"add new" forState:UIControlStateNormal];
add.frame = CGRectMake(100, 100, 100, 100);
[self.view addSubview:add];
- (void) aMethod:(id)sender
{
button[0].backgroundColor = [UIColor greenColor];
}
This is all my code for that button in my ViewController.m file... I have 1 warning and 1 error. My warning is
"method definition for 'aMethod' not found"
And this error is tagged under the line "#implementation ViewController" near the top of my code.
My error is
Use of undeclared identifier 'aMethod'
And this is tagged under my "-(void) aMethod: (id)sender"
And I have this in my ViewController.H file
- (void)aMethod;
No erros with that.. I have tried to get help with this before and I keep getting tips and edits that have to do with my programming syntax, But NO MATTER WHAT, i cant get rid of these errors. Is there anything else that could be wrong? Would it be helpful to see the rest of my program? And there is one more piece of info that could be of use. My entire program is written after one of initial lines that xcode sets me up with,
- (void)viewDidLoad
{
//my entire program is between these brackets.
}
When I try this code "-(void) aMethod: (id)sender{ }" before "viewdidload" i dont get an error. but when i put it after "-(void) aMethod: (id)sender{ }" i get the error. I figured that out when i was messing around trying to figure out what's wrong. Let me know if more info is needed. And by the way, i am trying to do it all programmatically, without ever using storyboard...Thank you so much in advance!!

Answer 1

change this in your .h file:
- (void)aMethod;
to this:
- (void)aMethod:(id)sender;
The actual method in your view controller (the .m file) should match this signature.

Answer 2

The "method definition for 'aMethod' not found" is not referring to your button but the fact you have defined the method aMethod in your header but you haven't implemented it in your implementation because you instead have -(void)aMethod:(id)sender;
edit:
Your code should look more like this:
-(void)viewDidLoad {
[super viewDidLoad];
UIButton *add = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[add addTarget:self action:#selector(aMethod:)forControlEvents:UIControlEventTouchDown];
[add setTitle:#"add new" forState:UIControlStateNormal];
add.frame = CGRectMake(100, 100, 100, 100);
[self.view addSubview:add];
}
- (void) aMethod:(id)sender {
button[0].backgroundColor = [UIColor greenColor];
}