How to initialize a property in iOS UITableViewController

Question

I am working on a UITableViewController

@interface GinkgoDeliveryOrdersTableViewController : UITableViewController

@property PFQuery * query;
@property NSArray * products;

@end

How shall I initialize these two properties? Currently, I am doing lazy initialization:

@implementation GinkgoDeliveryOrdersTableViewController

@synthesize query = _query;
@synthesize products = _products;

- (void) initQuery {
    _query = [PFQuery queryWithClassName:@"_Product"];
}

- (void) initProducts {
    if(! _query)
        [self initQuery];
    _products = [_query findObjects];
}

As a result, every time I want to use these two properties, I have to do something like this:

if(! self.products)
        [self initProducts];

and

if(! self.query)
        [self initQuery];

I feel I am doing something wrong here. Is there a cleaner way to do this? Thank you very much!

Answer 1

If the values are not being set from the outside then they shouldn't be read/write properties. Make them read-only and use lazy loading in the "getter" method.

@interface GinkgoDeliveryOrdersTableViewController : UITableViewController

@property (nonatomic, readonly) PFQuery * query;
@property (nonatomic, readonly) NSArray * products;

@end


@implementation GinkgoDeliveryOrdersTableViewController

@synthesize query = _query;
@synthesize products = _products;

- (PFQuery *)query {
    if (!_query) {
        _query = ...
    }

    return _query;
}

Do the same for the products getter.

Note that in your original code there was no need for the @synthesize lines but in this updated code they are needed because otherwise the ivar wouldn't be auto generated due to the explicit getter method.