Swift: David's Top 10 "Do This" List

DavidTop10

David's Top 10: Do That When Writing Swift

1) Purchase Dash (OS X and iOS) and get Swift from SwiftDoc.org (invaluable reference, I use it daily!)

2) Use Enums for UIView tags and SegmentedControl segments;

   enum MyViews: Int { case OKButton=1...} then switch MyViews(rawValue: view.tag)
   
 also for states (somewhat replaces C's X-Macros, helps during debugging)
 
   enum State: String {   case Idle = "Idle" ...} ; 
   let s: State = State(rawValue: "Idle")!; println("\(s.rawValue)") // Idle

3) When objects need configuration, you can use closures:

   lazy var object: Foo = { let foo=Foo(delegate: self); foo.x = "y"; return foo;} ()

   Benefit: moves "hidden" initializer code in viewDidLoad/etc to top of class.

4) Add main and after to your Code Snippets - big time saver if you use them often:
   main:
      dispatch_async(dispatch_get_main_queue()) { /* new line */ }
   after:
      let t = dispatch_time(DISPATCH_TIME_NOW, Int64(250 * NSEC_PER_MSEC))
      dispatch_after(t, dispatch_get_main_queue()) { /* new line */ }

5) Use same variable name with optional unwrapping (a 'best practice'): if let user = user {...

6) Use "#if true" and "if true" to your advantage. Former to enable/disable chunks of code (but leave them readable),
   the latter replaces C's "{...}" scoping blocks.

7) Switches are syntactic sugar for a list of if and else if statements - most probable should be first in performance 
   sensitive code. Long cases with a often hit default case can be a problem (C often uses jump tables for switches).

8) Never forget: Arrays, Dictionaries, and Sets are all values! If changing a structure in an array, 
   get it, change it, write it back.

9) Use the extended if let style (from Nate Cook, NSHipster), new in Swift 1.2:
   if let
       a = b where yada yada,
       c = d where blah blah // can prefix 'let if you really want to
   { // each clause must be unwrapping an optional with no general logic allowed except in the where section

10) Add a 'nullability' Code Snippet - then use it in your older Objective C code
    #if __has_feature(nullability) 
    NS_ASSUME_NONNULL_BEGIN
    #else
    // For Object pointers
    #define nullable
    #define nonnull
    // For C pointers
    #define __nullable
    #define __nonnull
    #endif

   #if __has_feature(nullability)
   NS_ASSUME_NONNULL_END
   #endif
   
Bonus read: Erica Sadun's "Don't do list"   http://ericasadun.com/2015/05/05/swift-dont-do-that/