IanKeen

NSDate *date = [NSDate date];
    
    NSTimeZone *timeZoneCST = [NSTimeZone timeZoneWithAbbreviation:@"CST"];
    NSTimeZone *timeZoneEST = [NSTimeZone timeZoneWithAbbreviation:@"EST"];
    
    NSDateFormatter *formatter = [NSDateFormatter new];
    formatter.dateStyle = NSDateFormatterShortStyle;
    formatter.timeStyle = NSDateFormatterShortStyle;
    
    formatter.timeZone = [NSTimeZone systemTimeZone];

IanKeen

Don't let your UIViewController think for itself...

Last time I showed you one strategy for trimming the fat from our view controller by seperating out protocols. In part 2 of this 3 part series we are going to use an architecture known as MVVM to dumb down our view controller. View controllers are usually filled with business rules, this is a problem for a number of reasons, two of which being:

• It makes the code harder to reason about; let the view controller worry about appearance and the business objects worry about the logic, we don't want them thinking for themselves ;)
• It makes your view controller bloated; business rules don't belong in your view controller

MVVM ?

MVVM stands for Model View ViewModel and is just a way of describing how to break up your interface, business rules and data so that they flow together in a logical, but seperated, way.

This is what that flow looks like

IanKeen

Make your UIViewController Awesynchronous!

Welcome back for the conclusion of this 3 part series! In part 1 we learnt how to slim down our view controllers to a manageable size. In part 2 we learnt how to strip out all the non-ui related logic. This time we are going to focus solely on the UITableView and how we can properly handle multiple asynchronous operations in its cells for maximum performance!

As always we will be starting with our project from last time.

What's making our table's scrolling so bad?

Our current implementation is very bad... our UITableViewCells are performing an expensive operation, and on the main thread no less!

The following code is currently in the setup method of our cell:

IanKeen

Put your UIViewcontroller on a diet

I hate to say it but our view controllers have gotten fat, and it's our fault! We feed them protocol after protocol, business rule after business rule. They don't know any better and they just gobble them all up...

This will be a 3 part "Tune up your table view" series in which we will take an old fat view controller, slim it down with some refactoring, freshen it up with some MVVM and then make it fly with some better asynchronous operation management!

In part 1 using refactoring and a couple of Interface Builder tricks hopefully I can provide some motivation to start your journey towards getting your view controllers back in fighting shape!

The current state of things...

UITableViews are pretty integral to most iOS apps so I'm going to use it as an example of how to change a 'fat' view controller into a 'slim' one.

IanKeen

protocol KeyValueStorable {
    subscript (key: String) -> AnyObject? { get set }
    mutating func removeAll() -> Void
}

extension NSUserDefaults: KeyValueStorable {
    subscript (key: String) -> AnyObject? {
        get { return self.objectForKey(key) }
        set { self.setObject(newValue, forKey: key) }

IanKeen

protocol DictionaryConvertable {
    static func fromDictionary(dictionary: [String: AnyObject]) throws -> Self
    func toDictionary() -> [String: AnyObject]
}
protocol DictionaryValueType {
    func dictionaryValue() -> AnyObject?
}

extension Optional: DictionaryValueType {
    func dictionaryValue() -> AnyObject? {

IanKeen

/**
* Usage: toString(object)
*/

public func toString(object: AnyObject) -> String {
    return toString(any: object, indent: 0)
}


private func indented(count: Int, string: String) -> String {

IanKeen

extension NSTimer {
    private class TimerClosure {
        private let closure: (NSTimer) -> Void
        init(closure: (NSTimer) -> Void) { self.closure = closure }
        @objc func selector(timer: NSTimer) { self.closure(timer) }
    }
    
    static func scheduledTimerWithTimeInterval(ti: NSTimeInterval, closure aClosure: (NSTimer) -> Void, userInfo: AnyObject?, repeats yesOrNo: Bool) -> NSTimer {
        let wrapped = TimerClosure(closure: aClosure)
        return NSTimer.scheduledTimerWithTimeInterval(ti, target: wrapped, selector: "selector:", userInfo: userInfo, repeats: yesOrNo)

IanKeen

extension String {
    func componentsSeparatedByStrings(separators: [String]) -> [String] {
        return separators.reduce([self]) { result, separator in
            return result.flatMap { $0.componentsSeparatedByString(separator) }
        }
        .map { $0.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceCharacterSet()) }
    }
}

/* Usage */

IanKeen

extension NSCoder {
    func encode(key: String, value: AnyObject?) {
        self.encodeObject(value, forKey: key)
    }
    func decode<T>(key: String) -> T? {
        return self.decodeObjectForKey(key) as? T
    }
}
extension NSCoding {
    func encode() -> NSData {