Access an objects property dynamically using a string with property name in Objective-C

Question

I have 2 objects, AddressBook and AddressCard. The AddressCard has the properties name, email, & birthday. The AddressBook has a lookup method that takes a string as an argument, and searches each added AddressCard for a match. In this lookup method I'd like to have an NSArray of each of the fields i'd like to search in the AddressCards. Then loop through each AddressBook entry test each field in my array for a match to the lookup's argument. The problem is I dont know how to access an objects property dynamically with a string - is this possible in Objective-C, or should I be trying to do this in a different way? I realize I could just use IF statements, but thats not a scalable solution.

Heres my lookup method:

-(AddressCard *)lookup:(NSString *)aName
{
    NSArray *fields = [[NSArray alloc] initWithObjects:@"name",@"email",@"birthday",nil];
    BOOL STATUS = NO;
    for(AddressCard *entry in book)
    {

        for(int i = 0; i < [fields count]; i++)
        {
            NSString *fieldName = [[NSString alloc] initWithString:[fields objectAtIndex:i]];
            NSRange range = [[entry fieldName]  rangeOfString:aName];

            if(range.location != NSNotFound)//Important to not directly test the NSRange struct, but one of its properties(BAD_ACCESS)
            {
                NSLog(@"'%@' found in field:%@ at range:%i,%i",aName,fieldName,range.location,range.length);
                STATUS = YES;
                return entry;
            }
            [n release];
        }

    }
    if(!STATUS)
        NSLog(@"'%@' not found in %@ address book",aName, bookName);

    return nil;
}

Any ideas or suggestions appreciated, thanks!

You are leaking fields and fieldName. In fact, you could use just NSString *fieldName = [field objectAtIndex:i];. You should perform a Build and Analyze. — dreamlax
– dreamlax, Commented Oct 18, 2010 at 20:57
the above wouldn't compile - n should be fieldName - I changed it when I copy/pasted it, but thanks you're right fields is leaking. :-) — desertmonad
– desertmonad, Commented Oct 18, 2010 at 21:04

Alejandro · Accepted Answer · 2010-10-18 20:52:47Z

4

The method you are looking for is valueForKey:

NSRange range = [[entry valueForKey:fieldName]  rangeOfString:aName];

answered Oct 18, 2010 at 20:52

Alejandro

3,7461 gold badge25 silver badges29 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

desertmonad Over a year ago

entry is the AddressCard object returned from enumerating through the array of AddressCards and doesnt have the valueForKey method?

Alejandro Over a year ago

as long as AddressCard inherits from NSObject and you declare your properties with @property, you get that for free (developer.apple.com/library/ios/#documentation/Cocoa/Conceptual/…)

desertmonad Over a year ago

Thank you for that -- now I have a new problem though, I'm getting this error:NSUnknownKeyException', reason: '[<AddressCard 0x100108dd0> valueForUndefinedKey:]: this class is not key value coding-compliant for the key birthday. I'm going to google this but I've never gotten that error..

desertmonad Over a year ago

I did print out the fields array and it does contain the strings which correspond to properties on the AddressCard class that were created with @property and @synthesize.

desertmonad Over a year ago

thanks - found the problem - birthday property is actually birthdate. *palmface.

Collectives™ on Stack Overflow

Access an objects property dynamically using a string with property name in Objective-C

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related