Custom getter not called in Objective C

Question

I'm trying to create a getter for a property - for the time being I'm just using the method to build up an NSMutableObject from static arrays but eventually these will be dynamic config settings. In a previous app and from getter and setters not working objective c I did this:

#import "ViewController.h"

@interface ViewController ()

@property (nonatomic) NSMutableDictionary *questions;

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    [[self questions] setValue:@"FOO" forKey:@"bar"];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

+ (NSMutableDictionary *)questions
{
    static NSMutableDictionary *_questions;
    if (_questions== nil)
    {
        NSArray *genders = @[@"male", @"female"];
        NSArray *ages = @[@"<10", @">60", @"Other"];
        _questions = [[NSMutableDictionary alloc] init];
        [_questions setValue:genders forKey:@"gender"];
        [_questions setValue:ages forKey:@"age"];

    }

    return _questions;
}

When I get to the line in viewDidLoad where I try to use the 'questions' property, it doesn't use the custom getter (it just assigns bar:FOO to a nil dictionary). What am I missing?

Answer 1

The reason your custom questions method is not being called through setValue:forKey: is that it is a class method:

+ (NSMutableDictionary *)questions is a method defined on the ViewController class, while the property accessor (which setValue:forKey: is looking for) is defined on the instance .

To access your custom method as it is currently defined call the class method:

[[[self class] questions] setValue:@"FOO" forKey:@"bar"];

This may not have the effect you intend, as this value will be shared across all instances of the class.

Answer 2

Try changing the

+ (NSMutableDictionary *)questions

To

- (NSMutableDictionary *)questions

You may also want to change the return type to NSDictionary * to prevent the static variable from being mutated, or return _questions.copy or _questions.mutableCopy