selector as parameter in IOS - ios

Question

I want to raise a different method for each created button.
I try to call "FirstImage" method in viewDidLoad but it doesn't work.
I have a problem with the selector in ViewDidLoad. Didn't recognise "FirstImage" which is a void method without parameter.
ViewController.m
- (void)createFirstButton:(NSString *)myName: (SEL *)myAction{
UIButton *btn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[btn addTarget:self
action:#selector(myAction)
forControlEvents:UIControlEventTouchUpInside];
[btn setTitle:myName forState:UIControlStateNormal];
btn.frame = CGRectMake(20, 916, 120, 68);
[self.view addSubview:btn];
}
- (void)viewDidLoad{
[self createFirstButton:#"First" myAction:[self FirstImage]];
}
What I have done (I changed "CreateFirstButton" into "CreateButton") :
ViewControler.m
#import "ViewController.h"
#interface ViewController ()
#end
#implementation ViewController
#synthesize myHeight;
#synthesize myWidth;
#synthesize myX;
#synthesize myY;
- (void)createButton:(NSString *)myName:(SEL)myAction:(NSUInteger)my_x:(NSUInteger)my_y:(NSUInteger)my_width:(NSUInteger)my_height
{
UIButton *btn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[btn addTarget:self
action:myAction
forControlEvents:UIControlEventTouchUpInside];
[btn setTitle:myName forState:UIControlStateNormal];
btn.frame = CGRectMake(my_x, my_y, my_width, my_height);
[self.view addSubview:btn];
}
- (void)myXcrementation{
myX = myX + 150;
}
- (void)viewDidLoad{
myX = 20; myY = 916; myWidth = 120; myHeight = 68;
[self createButton:#"First":#selector(FirstImage):myX:myY:myWidth:myHeight];
[self myXcrementation];
[self createButton:#"Previous":#selector(PreviousImage):myX:myY:myWidth:myHeight];
[self myXcrementation];
[self createButton:#"Pause":#selector(PauseImage):myX:myY:myWidth:myHeight];
[self myXcrementation];
[self createButton:#"Next":#selector(NextImage):myX:myY:myWidth:myHeight];
[self myXcrementation];
[self createButton:#"Last":#selector(LastImage):myX:myY:myWidth:myHeight];
}
- (void)FirstImage{
current = 0;
[self SetImage];
}
-(void)SetImage{
[myImageView setImage: [myArray objectAtIndex:(current)]];
}
#end
ViewController.h
#import <UIKit/UIKit.h>
#interface ViewController : UIViewController{
}
#property(assign, nonatomic) NSUInteger myHeight;
#property(assign, nonatomic) NSUInteger myWidth;
#property(assign, nonatomic) NSUInteger myX;
#property(assign, nonatomic) NSUInteger myY;
#end
I edited this post again and there is no more error.
Special thanks to everybody. It took me time to understand :)

Answer 1

You have to use use #selector as follows
[self createFirstButton:#"First" myAction:#selector(FirstImage)];
Then your signature is wrong, since SEL shouldn't be a pointer.
Change
- (void)createFirstButton:(NSString *)myName: (SEL *)myAction{
to
- (void)createFirstButton:(NSString *)myName: (SEL)myAction{
Finally myAction has type SEL so you can pass it directly to the UIButton method, as follows
[btn addTarget:self
action:myAction
forControlEvents:UIControlEventTouchUpInside];
Also, I'd like to add that using capitalized names for methods it's a very bad practice.

Answer 2

You should use
- (void)viewDidLoad{
[self createFirstButton:#"First" myAction:#selector(FirstImage)];
}
or
- (void)viewDidLoad{
[self createFirstButton:#"First" myAction:NSSelectorFromString(#"FirstImage")];
}
#selector(myAction) should be replaced with myAction, and (SEL *) should be replaced with SEL.
In your code, before -createFirstButton:myAction: is called, its second parameter [self FirstImage] would be evaluated(called) first. #selector() takes a name and returns a SEL.

Answer 3

Change the method literal as in the following
- (void)createFirstButton: (NSString *)myName withAction: (SEL)myAction
For both declaration and definition.
And also why have you declared the same method as a public as well as private?

Answer 4

Use
[self createFirstButton:#"First" withAction:NSSelectorFromString(#"FirstImage")];
And change the method name as :
- (void)createFirstButton:(NSString *)myName: withAction: (SEL) myAction{
UIButton *btn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[btn addTarget:self
action:myAction
forControlEvents:UIControlEventTouchUpInside];
[btn setTitle:myName forState:UIControlStateNormal];
btn.frame = CGRectMake(20, 916, 120, 68);
[self.view addSubview:btn];
}
Also,
I wonder-all buttons having same frame, if possible pass frame this method.

Answer 5

If you are looking to pass string as method name to selector, then use NSSelectorFromString. String should end with ':' Example-
NSString *myName=#"aMethod:";
[button addTarget:self
action:NSSelectorFromString(myName)
forControlEvents:UIControlEventTouchDown];