Swift for loop nested array performance

Question

Which is better performance?

Option 1

var sections: [SubMenu]

var selectedItem: BeverageItem? {
    var item: BeverageItem?
    for section in sections {
        for beverage in section.beverages {
            if beverage.isSelected {
                item = beverage
                break
            }
        }
    }
    return item
}

Option 2

var selectedItem: BeverageItem? {
    var item: BeverageItem?
    if let subMenuIndex = sections.index(where: { (subMenu) -> Bool in
        for beverage in subMenu.beverages {
            if beverage.isSelected {
                return true
            }
        }
        return false
    }) {
        let subMenu = sections[subMenuIndex]
        if let beverageIndex = subMenu.beverages.index(where: { (beverage) -> Bool in
            return beverage.isSelected
        }) {
            item = subMenu.beverages[beverageIndex]
        }
    }
    return item
}

If option 1 then where would you use option 2 and why?

How large are your arrays? Unless they are very large, the difference is probably negligible and you should use what you understand better. – For large arrays, use Instruments, profile and compare. — Martin R
– Martin R, Commented Sep 19, 2016 at 12:01
When it comes to performance questions, the answer always is: what did you measure? — vikingosegundo
– vikingosegundo, Commented Sep 19, 2016 at 12:14

Yury · Accepted Answer · 2016-09-19 12:08:11Z

1

For unsorted arrays here most simple efficient way (result equal to your first solution):

var sections: [SubMenu]

var selectedItem: BeverageItem? {
    for section in sections.reverse() {// remove .reverse() if you don't really need last existed section
        for beverage in section.beverages {
            if beverage.isSelected {
                return beverage
            }
        }
    }
    return nil
}

answered Sep 19, 2016 at 12:08

Yury

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