(Im)Proper way to end an iOS app . . .

I am very new to Swift and iOS programming in general, and I had a situation where I wanted to throw an exception to fail an app in an unacceptable situation, and all I knew to do was to call exit(1) in plain old C-fashion.  I put that in my code like on the first day, and I forgot about it.  Since then I have had a lot of bizarre problems with XCode like not running my tests and just logging weird errors like "Failed to bootstrap" and other things.  I finally figured out that was what was causing the errors, and instead I could use:

    fatalError(@autoclosure message: () -> String = default, file: StaticString = default, line: UInt = default)

E.G.

   fatalError("You did something dumb.");

and it accomplishes the same thing (tells me I have done something stupid), but now the debugger stops on that line of code so I remember exactly what I have done.

exit(int), don't use it.

By the way, this is something that only a developer could do, clearly this would not be the way to handle an unexpected user condition.

Preach it, brother.

I came across this post today.

I especially like this:  “There is a fundamental difference between the few developers that will become highly skilled and all the other copy and paste developers. The former know they lack knowledge and take the time to grow it. The latter never bother, they go on with what little they know, trying to hack together something and calling it a day.”

Life can be frustrating as a dig-in-and-find-out-how-it-works developer, but I have always admired someone who will dig into something, endure the frustration and "What were they thinking???!?" moments, and come out on the other side with an actual understanding of how something works.

Swift Protocol-Oriented programming

Apple makes a big deal about Protocols in swift and how they are better than anything else ever.  I found it quite irritating that nowhere in their explanation of what makes them so great did they mention that a protocol is eerily similar to an interface in Java.  Moving from a C++ background to Java, I was completely baffled why you would use an interface rather than an abstract class.  That question was answered back in 1997 when I started designing applications and APIs using interfaces first.  Nowadays, moving into swift, protocols certainly have features that interfaces do not - such as extensions and conditional conformance - but really - this is not something they just pulled out of nowhere.  I wish they didn't have to act like every thing they do is new and unprecedented.

It would be so much more honest for them to come out and say, "In designing a new language, we looked at what works in Java, Lisp, Python, (gasp) Perl, Haskell, Go, JavaScript - the needs of iOS and the environment apps find themselves in - and created a best-of-breed language."

Swift 2.0, Reference and Value Types, and Unintended Sharing.

I have recently begun learning swift 2.0, because I would like to build an iOS app and I really don't want to have to learn Objective-C.  I am trying to learn it the right way, which means understanding how the language works and not just mutating examples to learn by accident.

I have been reading a lot about structs and classes, and the difference between value types and reference types.  In short, classes pass around object references and structs make copies whenever you pass them around.  I visualize it in old-school terms:  Classes use pointers, but with structs the variable IS the data.

This seems pretty simple - especially if you are comfortable with object languages.  I have watched a few Apple videos, though, and they make it sound revolutionary.  This one in particular goes on about unintended sharing - I pass a handle to the same object into two different contexts where they are expected to be independent.  Change one, impact the other, etc.  His illustrative example was "I created a thermostat object, assigned it to my house.  Then I set the thermostat in my oven to 450, and my house caught on fire!"  Paraphrase.  Gag - what a juvenile way to introduce a language feature.  They could have at least used a real-world scenario they came across implementing their standard libraries that made this feature such a deal-maker.

This seems to me to be very valuable to a college student, or someone learning an object language coming from C, but really, is this that big of a deal?  I can honestly say that I haven't had a bug of this type in my code, that I have detected of course - for decades.  On the other hand, I just spent an agonizing couple of days trying to figure out why extremely routine code did not work.  Take this example:

var map = [String: [String: String]]();

var subMap = [String: String]();

map["map"] = subMap;

subMap["1"] = "2";

For those who don't know swift, this means create a map which can hold maps of string value/pairs.  Next, create a string value/pair map, and assign it to the key "map" in the top-level map.  Finally, assign the key/value entry "1" -> "2" into the sub map.  The expectation being that it will be reflected in the top-level map as well.  This is pretty standard in Java - I do it a lot so I can factor code which handles the sub trees into external code.  In this case, it doesn't work.  Because collections in swift are structs - I.E., value types - the assignment on the third line makes a copy which is unaffected by the assignment on line 4.  I came up with this working code after much hair-pulling:

var map: Dictionary = [String: [String: String]]();

map["map"]!["1"] = "2";

And only later uncovered the reason that I explained before.  I find this extremely annoying, but certainly manageable once you understand the language - and maybe even something you can use effectively.  But I found his example so contrived that I basically checked out.