Unrecognized selector sent to instance

Question

I'm having trouble with this method, more specifically I'm having trouble with my logic. I'm trying to combine two array's firstName and lastName both sequentially matching up. I was thinking I could us a for loop to iterate through the array count and then combine the array's using arrayByAddingObjectsFromArray.

Unfortunately it seems that this part throws up an error : __NSCFConstantString arrayByAddingObjectsFromArray:]: unrecognized selector sent to instance 0x10c824218

Any ideas why this is? What does it mean by selector; is that it doesn't like the array i'm trying to pass to it?

- (NSString *)badgeForSpeaker:(NSString *)speaker{


    NSArray *firstName = @[@"Adele", @"Edsger", @"Joan", @"Clarence", @"Margaret", @"George", @"Tim", @"Jean"];
    NSArray *lastName = @[@"Goldberg",@"Dijkstra",@"Clarke",@"Ellis",@"Hamilton",@"Boole",@"Berners-Lee",@"Bartik"];


    NSString *uppercaseString = [speaker copy];
    NSMutableString *hello = [[NSMutableString alloc]init];

    for (NSUInteger i =0; i < [lastName count] ; i++) {
        uppercaseString = [lastName[i] capitalizedString];
        hello = [@"Hello, my name is " mutableCopy];
        firstName = [firstName[i] arrayByAddingObjectsFromArray:lastName[i]];
        NSString *fullNameString = [firstName componentsJoinedByString:@" "];
        [hello appendFormat:@"%@",fullNameString];
        NSLog(@"%@",hello);

    }

    return hello;
}

firstName[i] returns NSString object. the method arrayByAddingObjectsFromArray belongs to NSArray — ProblemSlover, Oct 22 '15 at 17:07
My fault, I expect "hello" to return a String "Hello, my name is [firstName] [lastName]." — Diego Aguirre, Oct 22 '15 at 17:42
Possible duplicate of [How can I debug 'unrecognized selector sent to instance' error](https://stackoverflow.com/questions/25853947/how-can-i-debug-unrecognized-selector-sent-to-instance-error) — Cœur, Jul 08 '19 at 05:54

luckyShubhra · Accepted Answer · 2015-10-22T17:44:43.923

You are getting this error as arrayByAddingObjectsFromArray method is not defined for NSString object. You are trying to use this method with a NSSting object as first name[i] returns a NSString not an NSArray.

Why r u complicating things you can achieve the same by

NSArray *firstName = @[@"Adele", @"Edsger", @"Joan", @"Clarence", @"Margaret", @"George", @"Tim", @"Jean"];
    NSArray *lastName = @[@"Goldberg",@"Dijkstra",@"Clarke",@"Ellis",@"Hamilton",@"Boole",@"Berners-Lee",@"Bartik"];

    NSMutableArray *array = [[NSMutableArray alloc] init];
    NSString *hello;

    for (NSUInteger i = 0; i < [lastName count] ; i++) {
        NSString *fullName = [[[firstName objectAtIndex:i] uppercaseString]stringByAppendingString:[@" " stringByAppendingString:[[lastName objectAtIndex:i]uppercaseString]]];

        [array addObject:fullName];
        hello = [NSString stringWithFormat:@"Hello, my name is %@", fullName];
        NSLog(@"%@",hello);
    }

Hope it helps.. Happy Coding.. :)

Thanks for the help lucky! – Diego Aguirre Oct 23 '15 at 00:44 — Diego Aguirre, Oct 23 '15 at 00:44

Ty Lertwichaiworawit · Answer 2 · 2015-10-22T17:34:52.633

If I undestand correctly, you want the hello string to be

Hello, my name is Firstname Lastname

You can do this by:

NSArray *firstName = @[@"Adele", @"Edsger", @"Joan", @"Clarence", @"Margaret", @"George", @"Tim", @"Jean"];
NSArray *lastName = @[@"Goldberg",@"Dijkstra",@"Clarke",@"Ellis",@"Hamilton",@"Boole",@"Berners-Lee",@"Bartik"];

NSMutableArray *fullNameArray = [[NSMutableArray alloc] init];
NSString *hello;
NSString *uppercaseString = [speaker copy];

for (NSUInteger i = 0; i < [lastName count] ; i++) {

   uppercaseString = [lastName[i] capitalizedString];

   //join firstName and lastName in a string
   NSString *fullName = [[firstName objectAtIndex:i] stringByAppendingString:[NSString stringWithFormat:@" %@", uppercaseString]];

   //add fullName string to fullNameArray
   [fullNameArray addObject:fullName];

   //set it in hello string
   hello = [NSString stringWithFormat:@"Hello, my name is %@", fullName];

   NSLog(@"%@",hello);
}

Thanks tnylee, this definitely closer matches my original code and logic. Appreciate the help — Diego Aguirre, Oct 23 '15 at 00:46

score 1 · Answer 3 · answered Oct 22 '15 at 17:58

Method arrayByAddingObjectsFromArray: is used to connect two arrays. It works like this:

NSArray * first = @[@1, @2, @3]; //[1, 2, 3]
NSArray * second = @[@4, @5];    //[4, 5]
NSArray * bothArrays = [first arrayByAddingObjectsFromArray:second]; // [1, 2, 3, 4, 5]

If you really wanna use this method for this task, you can wrap strings into arrays, like this:

NSArray * fullNameComponents = [@[firstName[i]] arrayByAddingObjectsFromArray:@[lastName[i]]];

but it is like the most unefficient whay to do that. Much better is to create array instantly:

NSArray * fullNameComponents = @[firstName[i], secondName[i]];

In your case the best option will be to omit all the array job, and create your string using format:

NSString * hello = [NSString stringWithFormat:@"Hello, my name is %@ %@", firstName[i], secondName[i]];

Unrecognized selector sent to instance

3 Answers3