dmytro-anokhin

protocol Store {

    func fetch(_ completion: @escaping (_ result: Model?) -> Void)
}

class LocalStore: Store {
    
    func fetch(_ completion: @escaping (_ result: Model?) -> Void) {
        // Perform database operation
    }

dmytro-anokhin

class CompositeTableViewDataSource: UITableViewDataSource {
    // ...
}

class CompositeCollectionViewDataSource: UICollectionViewDataSource {
    // ...
}

class CompositeMapViewDelegate: MKMapViewDelegate {
    // ...

dmytro-anokhin

// Initialization of lock, pthread_rwlock_t is a value type and must be declared as var in order to refer it later. Make sure not to copy it.
var lock = pthread_rwlock_t()
pthread_rwlock_init(&lock, nil)

// Protecting read section:
pthread_rwlock_rdlock(&lock)
// Read shared resource
pthread_rwlock_unlock(&lock)

// Protecting write section:

dmytro-anokhin

class ThreadSafeCollection<Element> {
  
    // Concurrent synchronization queue
    private let queue = DispatchQueue(label: "ThreadSafeCollection.queue", attributes: .concurrent)
  
    private var _elements: [Element] = []
  
    var elements: [Element] {
        var result: [Element] = []
        

dmytro-anokhin

repeat {
    let oldValue = // read value (1)
    let newValue = // calculate new value
    let success = compareAndSwap(old: oldValue,
                                 new: newValue,
                                 current: /* read value (2) */)
} while (!success)

dmytro-anokhin

protocol ThreadSafeContainer: AnyObject {
  
    func read(_ closure: (_ object: Any?) -> Void)
  
    func write(_ closure: (_ object: Any?) -> Any?)
}

dmytro-anokhin

class ShapeView: UIView {
    var strokeColor: UIColor?
    var fillColor: UIColor?
}

class RectangleView: ShapeView {
    override func draw(_ rect: CGRect) {
        // Drawing a rectangle
    }
}

dmytro-anokhin

protocol ShapeViewDelegate {
    func drawShapeView(_ shapeView: ShapeView)
}

class ShapeView: UIView {
    var strokeColor: UIColor?
    var fillColor: UIColor?
    
    var delegate: ShapeViewDelegate? {
        didSet {

dmytro-anokhin

@import Foundation;

NS_ASSUME_NONNULL_BEGIN


@class MyClass // Forward declaration required by the compiler
    
@protocol MyDelegate <NSObject>

- (BOOL)myClass:(MyClass *)myClass shouldProcessEvent:(id)event;

dmytro-anokhin

protocol MyDelegate : AnyObject {
    func myClass(_ myClass: MyClass, shouldProcessObject object: Any) -> Bool
}

class MyClass : NSObject {
    weak var delegate: MyDelegate?
}