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1. Cast

   if ("ABCDE" as NSString).containsString("BC") {
       println("Containing")
   }
   

2. dispatch groups

   let group = dispatch_group_create()
   let mainQueue = dispatch_get_main_queue()
   
   for i in 1...10 {
   
       dispatch_group_enter(hgReadGroup)
   
       longSubTask(param:String, completionHandler: { (results) -> () in
           // ...
           dispatch_group_leave(group)
       })
   }
   
   dispatch_group_notify(group, mainQueue) {
       print("-> all subtasks are finished")
       completionHandler(entries:entries)
   }
   

3. Introspection

   let date = NSDate()
   let name: AnyClass! = object_getClass(date) // __NSDate
   
   let string = "Hello"
   let name = string.dynamicType // Swift.String
   

   also:

   class MyClass { }
   
   let o : AnyObject = MyClass()
   
   print(o is String) // false
   print(o is MyClass) // true
   

4. JSON deserialization in guard

   guard let data = optionalData,
      optionalDict = try? NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers) as? [String:AnyObject],
      d = optionalDict,
      latestVersionString = d["latest_version_string"] as? String,
      latestVersionURL = d["latest_version_url"] as? String else {
      return
   }
   

5. Lazy initialize static variable

   static var x = {
       // ...
       return xxx 
   }()
   

6. Objective-C flags

   let date = NSDate()
   let unitFlags: NSCalendarUnit = [.Hour, .Day, .Month, .Year]
   let components = NSCalendar.currentCalendar().components(unitFlags, fromDate: date)
   

7. Open the REPL

   $ xcrun swift
   Welcome to Swift!  Type :help for assistance.
     1> var x = "toto"
   x: String = "toto"
     2> println(x)
   toto
     3>  
   

8. Properties initialization with code

   private var stravaAPI : StravaAPI = {
       return StravaAPI()
   }()
   

9. Public property with private setter

   public class Person {
       public private(set) var name: String
       // ...
   }
   

10. Standalone file

    #!/usr/bin/swift
    
    /*
     $ swift x.swift
    */
    
    import Foundation
    
    for arg in Process.arguments {
        print(arg)
    }
    

11. Static instance

    static let dateFormatter: NSDateFormatter = {
        let df = NSDateFormatter()
        df.dateFormat = "yyyyMMdd"
        return df
    }()
    

12. subscript

    struct Board {
    
        var cells : [[Int]]
    
        init(row:Int, columns:Int) {
            self.cells = [[Int]]()
            for _ in 0..<row {
                self.cells.append([Int](count: columns, repeatedValue: 0))
            }
        }
    
        subscript(row: Int, column: Int) -> Int {
            get {
                return cells[row][column]
            }
    
            set {
                cells[row][column] = newValue
            }
        }
    }
    
    var b = Board(row: 3, columns: 4)
    
    b[1,1] = 1
    
    print(b[1,1])
    

13. Swift script

    #!/usr/bin/env xcrun --toolchain com.apple.dt.toolchain.XcodeDefault swift
    
    // -F/my/frameworks               add to search path
    // -framework MyUtils.framework   load framework
    // -D FLAG                        compilation flag
    
    import Foundation
    
    print(CommandLine.arguments)
    

14. Swift Singleton

    class MyClass {
        static let sharedInstance = MyClass()
    }