CR204-1.swift

// This is meant to go along with Coder Radio Episode 204 
// Optional types in Swift 101

struct JarJar {
  var senateSpeach: String? // the '?' means messa might be nil and makes me an Optional type
  
  func voteOfNoConfidence() {

    // attempting to use the senateSpeach var but not setting it's value    
    let isSith = senateSpeach?.containsString("something something darkside") // senateSpeach is nil
    // the '?' let's the compiler know that we're not sure about that slippery senateSpeech, so if it's nil this won't crash
    // we should note that isSith is a Bool but doesn't default ot false in this case, instead it's nil / 'invalid'
  }
  
  func insaneVoteOfConfidence() {
      // attempting to use the senateSpeach var but not setting it's value
    let isSith = senateSpeach!.containsString("messa gonna burn this mother down!") // senateSpeach is still nil...
    // the '!' let's the compiler now that we are 'SURE' that senateSpeach isn't nil -- this is called force unwrapping
    // this is suicide...  we are force unwrapping an optional that we have no reason to think or guarantee that it's not nil
    // this code will crash with: "fatal error: unexpectedly found nil while unwrapping an Optional value"
    // in general force unwrapping should be done sparingly and only if you're 100% sure that the value isn't nil
  }
  
}

CR204-2.m

// this is the rough ObjC equivelant to the Swift above. I have ignored a header and truncated some code for brevity
// for the purposes of this sample we'll ignore the differences between Swift String and NSString
@interface JarJar()

@property(nonatomic, weak) NSString *senateSpeach;

@end

@implementation JarJar

- (void)voteOfNoConfidence() {
  // to get the nil protection '?' in Swift gives, we'd need to manually implement a nil check
  if(_senateSpeach != nil) {
    BOOL isSith = [_senanteSpeach containsString:@"something something darkside"]; 
  }
}

- (void)insaneVoteOfConfidence() {
      // '!' is Swift has the same effect as just going sans a nil check in ObjC
      BOOL isSith = [_senanteSpeach containsString:@"something something darkside"]; 
      // this crashes and burns
}

@end

So the objc version isSith is not defined if _senateSpeach == nil. From reading the swift version if senateSpeach == nil then isSith would be defined and assigned the value of nil. A bit of a difference. I don't know how much of a fan I am of optionals. I haven't written a lot of swift but I could see it leading to unintended nil propagation.

Also, more coding examples on the show! and Jar Jar references!

When you have to do a lot of parsing, where some values will inevitably be null (or "nil"), this is a very useful feature, especially if you have some logic taking care of the nulls. I'm glad C# 6.0 got this as well.