Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

iOS Swift Functions and Optionals Parameters and Tuples Decomposing a Tuple

Posted by Chepu Lee
Chepu Lee
1,007 Points

Extra Credit

Hello everyone, I've tried to solve this Extra Credit problem, but still don't have any idea...

"Write a function that accepts a Dictionary as parameter and returns a named tuple. The dictionary should contain the following keys: title, artist and album."

Would you please help me or give me some clues? Thanks a lot :)

1 Answer

Richard Lu
Richard Lu
20,185 Points
Richard Lu
Richard Lu
20,185 Points

Hey Chepu,

Here's my approach to the problem assuming that the dictionary passed from the parameter has all three of these keys, and the dictionary is of type [String: String].

func afunction(aDict: [String: String]) -> (title: String, artist: String, album: String) {
   // This function could of been written in one line, but i've separated it to make it more clear.
   // if it were to be in one line it would look like this
   // return (aDict["title"]!, aDict["artist"]!, aDict["album"]!)

   let title = aDict["title"]!
   let artist = aDict["artist"]!
   let album = aDict["album"]!

   return (title, artist, album)
}

otherwise, another solution would be

func afunction(aDict: [String: String]) -> (title: String?, artist: String?, album: String?) {
    // This function could of been written in one line, but i've separated it to make it more clear.
    // if it were to be in one line it would look like this
    // return (aDict["title"], aDict["artist"], aDict["album"])

    let title = aDict["title"]
    let artist = aDict["artist"]
    let album = aDict["album"]

    return (title, artist, album)
}

if there are any questions, feel free to ask! :)

Ryan Watson
Ryan Watson
1,472 Points
Ryan Watson
Ryan Watson
1,472 Points

Quick question - the first solution includes a "!" after each of the declared constants in the function, and the second a "?" after the tuple names. Just not following the rationale there (possible we've just not covered it yet in the course).

Richard Lu
Richard Lu
20,185 Points
Richard Lu
Richard Lu
20,185 Points

Hey Ryan,

Short answer:

! - never nil and ? - may either be a nil or some value

Here's a simple example

var (x, y): (Int?, Int?) = (5, nil)

print(x)   // prints out optional(5)
print(y)   // prints out nil

y = 10  // assigned y to 10 (not nil anymore)
print(y)   // prints out optional(10)

print(x!) // prints out 5     the '!' is 'like' asserting x will NEVER be nil (very dangerous if not checked)
print(y!) // prints out 10    the '!' is 'like' asserting y will NEVER be nil (very dangerous if not checked)

Note this since they do speak of it in the videos

var (x, y) : (Int?, Int?)

and

var z : (Int, Int)?

are not the same

Let me know if that makes sense. Happy coding! :)