Get string value of class propery names in Objective-C

Question

I have the following class definition.

Contact.h

#import <CoreData/CoreData.h>


@interface Contact :  NSManagedObject  
{
}

@property (nonatomic, retain) NSString * City;
@property (nonatomic, retain) NSDate * LastUpdated;
@property (nonatomic, retain) NSString * Country;
@property (nonatomic, retain) NSString * Email;
@property (nonatomic, retain) NSNumber * Id;
@property (nonatomic, retain) NSString * ContactNotes;
@property (nonatomic, retain) NSString * State;
@property (nonatomic, retain) NSString * StreetAddress2;
@property (nonatomic, retain) NSDate * DateCreated;
@property (nonatomic, retain) NSString * FirstName;
@property (nonatomic, retain) NSString * Phone1;
@property (nonatomic, retain) NSString * PostalCode;
@property (nonatomic, retain) NSString * Website;
@property (nonatomic, retain) NSString * StreetAddress1;
@property (nonatomic, retain) NSString * LastName;

@end

Is it possible to obtain an array of NSString objects with all of the properties by name?

Array would look like this...

[@"City", @"LastUpdated", @"Country", .... ]

Solution (updated based on comment)

Thanks to Dave's answer I was able to write the following method to be used

- (NSMutableArray *) propertyNames: (Class) class { 
    NSMutableArray *propertyNames = [[NSMutableArray alloc] init];
    unsigned int propertyCount = 0;
    objc_property_t *properties = class_copyPropertyList(class, &propertyCount);

    for (unsigned int i = 0; i < propertyCount; ++i) {
        objc_property_t property = properties[i];
        const char * name = property_getName(property);
        [propertyNames addObject:[NSString stringWithUTF8String:name]];
    }
    free(properties);
    return [propertyNames autorelease];
}

You should return [propertyNames autorelease]; to follow memory management guidelines. Also, why not just pass in a Class object instead of a string to convert to a Class object? — Dave DeLong
– Dave DeLong, Commented Jun 8, 2010 at 22:49
This should also be a free function or a class method, rather than an instance method. — dreamlax
– dreamlax, Commented Jun 9, 2010 at 4:04
@dreamlax does having it as a class method make much of a difference if I am using it privately within a singleton? (still new in objc) — Chris Wagner
– Chris Wagner, Commented Jun 9, 2010 at 4:16
It is more logical for it to be a class method because it doesn't depend on the state of an instance (it doesn't reference any instance variables). If a method doesn't depend on the state of an instance, it should be a class method. The output is entirely dependent only on the class parameter, so it should be a class method or free function. Alternatively you could make it a class category method that operates on the current class. — dreamlax
– dreamlax, Commented Jun 9, 2010 at 4:36
Well, actually that's not entirely true, but generally speaking it is the case. — dreamlax
– dreamlax, Commented Jun 9, 2010 at 4:41

Dave DeLong · Accepted Answer · 2010-06-08 22:02:39Z

5

Yep! Here you go:

#import <objc/runtime.h>

//somewhere:
unsigned int propertyCount = 0;
objc_property_t * properties = class_copyPropertyList([self class], &propertyCount);

NSMutableArray * propertyNames = [NSMutableArray array];
for (unsigned int i = 0; i < propertyCount; ++i) {
  objc_property_t property = properties[i];
  const char * name = property_getName(property);
  [propertyNames addObject:[NSString stringWithUTF8String:name]];
}
free(properties);
NSLog(@"Names: %@", propertyNames);

Warning: code typed in browser.

answered Jun 8, 2010 at 22:02

Dave DeLong

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Comments

Alex · Accepted Answer · 2010-06-08 21:42:46Z

2

You could call dictionaryWithValuesForKeys: and then call the allValues method on that dictionary to get an array of values. Note that you'll need to convert the non-NSString properties to strings yourself.

answered Jun 8, 2010 at 21:42

Alex

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2 Comments

Dave DeLong Over a year ago

That gives you the values of the specified keys. It seems like @Flash84x wants a list of keys.

Chris Wagner Over a year ago

What would I pass to dictionaryWithValuesForKeys:?

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