Dynamically changing cell.update Date function? - ios

Question

I am only new to all this so forgive my ignorance! I have a Table View to which I call a cell update method every time I open the Scene (it's sorted by date). I am trying to dynamically show a different date format depending on the when the Object was last edited. Example: Show time if date is today, Show "Yesterday" if date was yesterday etc. My question is - What is the best way to write this and is calling the below func in my cell.update call going to be memory intensive? How can I write this better? Any help would be greatly appreciated!
func update(with fitnessInfo: Fitness) {
if let date = fitnessInfo.dateEdited as Date? {
let today = Calendar.current.isDateInToday(date)
let yesterdayFunc = Calendar.current.isDateInYesterday(date)
let yesterday = date.addingTimeInterval(172800)
let withinSevenDays = date.addingTimeInterval(604800)
let dateFormatter = DateFormatter()
func setdate(_ dateFormatter: DateFormatter) {
let convertedDate = dateFormatter.string(from: date)
fitnessDateLabel.text = convertedDate
}
if today == true {
dateFormatter.dateFormat = "h:mm a"
setdate(dateFormatter)
} else if yesterdayFunc == true {
fitnessDateLabel.text = "Yesterday"
} else {
switch date {
case yesterday...withinSevenDays:
dateFormatter.dateFormat = "EEEE"
setdate(dateFormatter)
default:
dateFormatter.dateFormat = "MMMM dd, yyyy"
setdate(dateFormatter)
}
}
}
Here is the Table View func (cellForRowAt) which this is called from.
tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: “fitnessCell", for: indexPath) as! FitnessTableViewCell
let fitnessInfo = fetchedRC.object(at: indexPath)
cell.update(with: fitnessInfo)
return cell
}

Answer 1

If code works it can not be bad.
It's a good idea to write unit- and performance-tests before any performance optimization. So you will see that your changes don't affect result and give performance improvement. Also you can use Xcode instruments to understand how exactly your code use CPU and memory by click Product->Profile and select Time profile and Allocations instruments. Don't forget that performance optimization is often a tradeoff between memory and CPU usage.
You should separate logic from presentation. So you be able to write unit-test. Also you can retain DateFrommater statically instead of initialize it each time you draw a cell. Here is an example how it can be done:
final class DateMapper {
static let todayDateFormatter = DateFormatter()
static let lastWeekAgoDateFormatter = DateFormatter()
static let moreThanWeekAgoDateFormatter = DateFormatter()
let today: Date
let currentCalendar = Calendar.current
init(today: Date) {
self.today = today
DateMapper.todayDateFormatter.dateFormat = "h:mm a"
DateMapper.lastWeekAgoDateFormatter.dateFormat = "EEEE"
DateMapper.moreThanWeekAgoDateFormatter.dateFormat = "MMMM dd, yyyy"
}
func formattedDate(date: Date) -> String {
guard let totalDays = currentCalendar.dateComponents([.day], from: date, to: today).day else {
return ""
}
switch totalDays {
case 0:
return DateMapper.todayDateFormatter.string(from: date)
case 1:
return "Yesterday"
case 2...7:
return DateMapper.lastWeekAgoDateFormatter.string(from: date)
default:
return DateMapper.moreThanWeekAgoDateFormatter.string(from: date)
}
}
}
This class can be used at your update method like this:
func update(with fitnessInfo: Fitness) {
let dateMapper = DateMapper(today: Date())
fitnessDateLabel.text = dateMapper.formattedDate(date: fitnessInfo.dateEdited)
}
Or you can retain DateMapper at ViewController and use it directly at cellForRowAt.
This class can be covered with unit test:
class ExampleTests: XCTestCase {
var dateMapper: DateMapper {
let todayStub = dateStubByComponents(year: 2019, month: 5, day: 4, hour: 12)
return DateMapper(today: todayStub)
}
func testTodayDate() {
// arrange
let todayStub = dateStubByComponents(year: 2019, month: 5, day: 4, hour: 11)
// act
let result = dateMapper.formattedDate(date: todayStub)
// assert
XCTAssertEqual(result, "11:00 AM")
}
func testYestadayDate() {
// arrange
let yesterdayStub = dateStubByComponents(year: 2019, month: 5, day: 3, hour: 0)
// act
let result = dateMapper.formattedDate(date: yesterdayStub)
// assert
XCTAssertEqual(result, "Yesterday")
}
func testLastWeekDate() {
// arrange
let lastWeekStub = dateStubByComponents(year: 2019, month: 5, day: 2, hour: 0)
// act
let result = dateMapper.formattedDate(date: lastWeekStub)
// assert
XCTAssertEqual(result, "Thursday")
}
func testPerformanceExample() {
let lastWeekStub = dateStubByComponents(year: 2019, month: 5, day: 2, hour: 0)
self.measure {
_ = dateMapper.formattedDate(date: lastWeekStub)
}
}
// MARK: Private
private func dateStubByComponents(year: Int, month: Int, day: Int, hour: Int) -> Date {
var dateStubComponents = DateComponents()
dateStubComponents.year = year
dateStubComponents.month = month
dateStubComponents.day = day
dateStubComponents.hour = hour
guard let dateStub = Calendar.current.date(from: dateStubComponents) else { fatalError("Date must be valid") }
return dateStub
}
}
At console you will see how long will take to transform Date to String:
values: [0.000922, 0.000063, 0.000041, 0.000038, 0.000036, 0.000035,
0.000035, 0.000036, 0.000043, 0.000027]