Do you consider yourself a Swift Ninja? Take our programming challenge! Beginners are also welcome to follow through and learn the craft.
Your solution of the challenge 2 doesn’t really answer the point “If no parameters pass to the function, it will return the string “none”.” but more “If the sum of the 2 strings is empty then return none”
Would it be more correct to write this ?
func flexStrings(s1 s1: String = “none”, s2: String = “”) → String {
return s1 + s2
}
Yeah that’s a nice solution - and shorter too 
please someone explain to me how challenge one works. How on earth does rearranging a tuple swap the values of two variables?? I understand tuples (i thought), inout functions etc. I feel like ive never encountered this before however.
var x = 1
var y = 2
how does
(x,y) = (y,x)
have anything to do with the values assigned to x and y?
Imagine tuples like little anonymous arrays (like closures are anonymous functions - you construct them only to use them once - most often to assign them to a variable).
You can access the members of a tuple by their numeric index (since they are not named)
so (x, y) = (y, x) becomes → (anonymous1.0, anonymous1.1) = (anonymous2.0, anonymous2.1)
so then anonymous2.0 and anonymous2.1 get assigned the values of x and y, and then those are assigned to anonymous1.0 and anonynous1.1
Finally since the two members of anonymous1 are in fact the variables x and y, you get the final values assigned to those two variables…
Three things on Challange #3:
1 . There is a known memory leak issue when using optional binding with switch like in the solution.
[SR-1339] `switch` statement memory leak (again) · Issue #43947 · apple/swift · GitHub
2 . For people (like me) who like to avoid Any anywhere possible might have found that let result1 = sumAny(Double(), 10, "-10", 2) prints 2 instead.
This is because that’s how NSNumber behaves when the fractional digit is 0. It just drops it.
print((1.0 as? NSNumber) as? Int) // Optional(1)
print(1.0 as? Int) // nil
3 . The map is unnecessary since in reduce, one can just return the input number like so
func sumAny(params: Any...) -> String {
return String(params.reduce(0) {
if let string = $1 as? String {
if string.isEmpty {
return $0 - 10
} else if let int = Int(string) where int > 0 {
return $0 + int
}
} else if let int = $1 as? Int {
return int == 0 ? $0 - 10 : $0 + int
}
return $0
})
}
Not a huge fan of the solution for #4.
I don’t think the solution is “Swifty” at all. It’s just general programming challenge. No reason to be on this thread…
I think introducing stride would make it more Swifty like so:
func countFrom(from: Int, to: Int) {
assert(from < to)
print(from.stride(through: to, by: 1).reduce("") { return $0+"\($1)" })
}
Plus, since the original post is old, print no longer prints in-line, but adds a line break at the end. So for the current 2.2 syntax, the following would be the correct answer:
func altCountFrom(from: Int, to: Int) {
guard from <= to else { return }
print(from, terminator: from < to ? "" : "\n")
altCountFrom(from+1, to: to)
}
Challenge 2: Can it also be implemented in this way? using variadic parameter feature in swift
func concatenateString(_ colors: String...) -> String{
return colors.count>0 ? String(colors.flatMap { String.CharacterView($0)}) : "None"
}
var result = concatenateString()
result = concatenateString("Red","Blue")
The answer for challenge 2, while definitely “swifty”, could be much simpler in order to complete the challenge as stated:
func params(s1: String = “none”, s2: String = “”) → String {
return(s1+s2)
}
This tutorial is more than six months old so questions are no longer supported at the moment for it. Thank you!