Objective-C: passing a string parameter to tapgesture @selector

Question

What I am trying to achieve is this: when I tap an specific UIImageView, the UITapGesture will pass a string into the tap method.

My code follows below: Imagine I have an UIImageView object there already, and when I tap this image, it will make a phone call,

UITapGestureRecognizer *tapFirstGuy = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(makeCallToThisPerson:@"1234567")];
[imageViewOne addGestureRecognizer:tapFirstGuy];

- (void)makeCallToThisPerson:(NSString *)phoneNumber
{
    NSString *phoneNum = [NSString stringWithFormat:@"tel:%@", phoneNumber];
    [[UIApplication sharedApplication] openURL:[NSURL URLWithString:phoneNum]];
}

However, I am getting the following compile error: @selector(makeCallToThisPerson:@"1234567");

I cannot figure what is happening. Why can't I pass string to the private method?

Answer 1

One more way you can try writing subclass of UITapGestureRecognizer like that below:-

@interface customTapGestureRecognizer : UITapGestureRecognizer

@property (nonatomic, strong) NSString * phoneNumber;

@end


// customTapGestureRecognizer.m

@implementation customTapGestureRecognizer

@end


// =====================

....

customTapGestureRecognizer *singleTap = [[customTapGestureRecognizer alloc] initWithTarget:self action:@selector(makeCallToThisPerson:)];

singleTap.phoneNumber = @"1234567";


-(void) makeCallToThisPerson:(UITapGestureRecognizer *)tapRecognizer {

customTapGestureRecognizer *tap = (customTapGestureRecognizer *)tapRecognizer;

NSLog(@"phoneNumber : %@", tap.phoneNumber);

}

Note:- The advantages of writing subclass is that you can pass more number of data easily in your UITapGestureRecognizer.

Answer 2

This is wrong, It's not a valid selector.

    UITapGestureRecognizer *tapFirstGuy = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(makeCallToThisPerson:@"1234567")];

You need to change to this:

 UITapGestureRecognizer *tapFirstGuy = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(makeCallToThisPerson:)];

In your methods the parameter will be the tapGesture, that's it:

 - (void)makeCallToThisPerson:(UITapGestureRecognizer *)tapGesture

You can do several things, in order to pas a parameter:

1.- Use de tag of the imageView, the tapGesture knows the view than it´s attached you can use the tag view:

 UITapGestureRecognizer *tapFirstGuy = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(makeCallToThisPerson:)];
         imageViewOne.tag = 1234567
        [imageViewOne addGestureRecognizer:tapFirstGuy];

- (void)makeCallToThisPerson:(UITapGestureRecognizer *)tapGesture
 {
NSString *phoneNum = [NSString stringWithFormat:@"tel:%ld",tapGesture.view.tag];
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:phoneNum]];
 }

Other option, subclassing in order to attach a NSString to imageView as a new property.