CODEWITHSUNDEEP
objective-cxcode
Joel Derfner
Joel Derfner

Reputation: 2207

error using selector as an argument

I'm setting up a UINavigationBar and am having trouble with the buttons. When I do this:

-(void)addLeftButton:(NSString *)titl
{
UIBarButtonItem *button = [[UIBarButtonItem alloc] initWithTitle:titl style:UIBarButtonItemStyleBordered target:self action:@selector(haikuInstructions)];
self.titleOfNavItem.leftBarButtonItem = button;
}

Then everything turns out fine. But if I do this:

-(void)addLeftButton:(NSString *)titl callingMethod:(NSString *)method
{
UIBarButtonItem *button = [[UIBarButtonItem alloc] initWithTitle:titl style:UIBarButtonItemStyleBordered target:self action:@selector(method)];
self.titleOfNavItem.leftBarButtonItem = button;
}

and call the method in another method like this:

[self addLeftButton:@"Instructions" callingMethod:@"haikuInstructions"];

I get an unrecognized selector error. Any thoughts about what I'm doing wrong?

Upvotes: 0

Views: 47

Answers (1)

Johnnywho
Johnnywho

Reputation: 5539

You should use NSSelectorFromString(NSString *aSelectorName):

UIBarButtonItem *button = [[UIBarButtonItem alloc] initWithTitle:titl style:UIBarButtonItemStyleBordered target:self action:NSSelectorFromString(method)];

EDIT: To elaborate, @selector directive will treat name between parenthesis literally. What's more, it won't check if that method really exists. This means if you use @selector(method) and have also variable NSString *method = @"haikuInstructions" you won't point to selector named "haikuInstructions", but to selector named "method".

Upvotes: 3

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