Question

I have a working app which has a plist as data container. An array of dictionaries is generated from the plist in viewdidload. Three different sub-arrays are generated from the main array depending on segmented control selection and objectforkeys. These arrays then populate a UIickerView.

While using this app user will select different segment each time and the app then has to step through the whole array each time to generate required sub-array.

Should I just go ahead and generate these sub-arrays once in viewdidload, so that they don’t have to be generated repeatedly?

This is not a big file (100 dictionaries). Will it improve overall efficiency of the app?

Answer 1

You could iterate collections numbering in the hundreds on every user action and not notice it, but it’s also very easy to cache the sub-arrays with a property.

Lazy init is a nice pattern here….

@property (nonatomic, strong) NSArray *myFilteredArray;
//...
@synthesize myFilteredArray=_myFilteredArray;

- (NSArray *)myFilteredArray {

    if (!_myFilteredArray) {
        NSMutableArray *array = [NSMutableArray array];
        // add to array using the filter logic you have already
        _myFilteredArray = [NSArray arrayWithArray:array];
    }
    return _myFilteredArray;
}

If nothing else, this makes your filtering code easy to find, and separate for each array, which might be prettier than burying it all in viewDidLoad.