CODEWITHSUNDEEP
objective-cparameter-passingselector
megara
megara

Reputation: 97

how to create a method with a selector parameter

Hi I'm trying to make an objective-C method that has a selector as parameter. But I keep receiving the "unrecognized selector sent to instance " error message. I'm doing the following:

this is the method with the selector parameter:

-(void)createURL: (SEL) selector{ 
dispatch_sync(kBgQueue,^{
NSData* data = [NSData dataWithContentsOfURL: wcfURL];
    [self performSelectorOnMainThread:@selector(selector)
                           withObject:data waitUntilDone:YES];


});
}

this is the method i want to be the selector:

-(void)fetchedUserType:(NSData *)responseData{

NSError* error;
NSDictionary* json = [NSJSONSerialization JSONObjectWithData:responseData
                                                     options:kNilOptions
                                                       error:&error];

userType = [json objectForKey:@"getUserTypeResult"];
}

and this is where I'm calling my method:

- (void)viewDidLoad
{
[super viewDidLoad];
NSString *url = [NSString stringWithFormat:@"http://10.211.55.3:1234/Service1.svc/getUserType/%@", userEmail];
wcfURL = [[NSURL alloc]initWithString:url];
SEL sel = NSSelectorFromString(@"fetchedUserType:");
[self createURL:sel];

}

Upvotes: 3

Views: 4339

Answers (1)

Anoop Vaidya
Anoop Vaidya

Reputation: 46563

EDIT 1:

Your error is here:

 [self performSelectorOnMainThread:@selector(selector)
 ----------------------------------^^^^^^^^^^^^^^^^^^^

selector is already a selector, and your are putting it in @selector() again.

It should be 

 [self performSelectorOnMainThread:selector withObject:data waitUntilDone:YES];

Edit 0:

Your codes are correct. And you get the error only when your SEL method in not found in the current class.

As in the code below, if I change the method name sum to add this will throw the same error.

-(void)sum{
    NSLog(@"sum");
}

-(void) createURL: (SEL) selector{
    [self performSelector:selector];
}

- (IBAction)total:(id)sender {
    SEL sel = NSSelectorFromString(@"sum");
    [self createURL:sel];
}

Also, you need to meet the method signature as well. If your method takes one argument, You need to send exactly one.

-(void)sum:(id)integer{
    NSLog(@"sum:%ld",[integer integerValue]);
}

-(void) createURL: (SEL) selector{
    //NSData* data = [NSData dataWithContentsOfURL: nil];
    //[self performSelectorOnMainThread:@selector(selector) withObject:data waitUntilDone:YES];

    [self performSelector:selector withObject:@(12)];
}

- (IBAction)total:(id)sender {
    NSInteger total=0;

    for (id element in self.arrayController.arrangedObjects) {
        total += [element firstNumber]*[element secondNumber];
    }
    [self.label setStringValue:[NSString stringWithFormat:@"%ld",total]];


    SEL sel = NSSelectorFromString(@"sum:");
    [self createURL:sel];

}

Upvotes: 4

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