Is there any difference between the following?
var array1_OfStrings = [String]()
var array2_OfStrings: [String] = []
var array3_OfStrings: [String]
Testing in Playground shows that 1 and 2 are the same but 3 behaves differently.
Can someone explain me the difference please? And also what will be the preferred way to declare an empty array of String?
First two have the same effect.
declare a variable array1_OfStrings, let it choose the type itself. When it sees [String](), it smartly knows that's type array of string.
You set the variable array2_OfStrings as type array of string, then you say it's empty by []
This is different because you just tell you want array3_OfStrings to be type array of string, but not given it an initial value.
I think the first one is recommended as The Swift Programming Language uses it more often.
While I might be late to the party, there is one thing that needs to be said.
First option set array1_OfStrings to array of Strings
The other option tells that array1_OfStrings is array of Strings and then set it empty.
While this might be a really small difference, you will notice it while compiling. For the first option compiler will automatically try to find out what is the type of array1_OfStrings. Second option won't do that, you will let compiler know that this actually is array of Strings and done deal.
Why is this important? Take a look at the following link:
https://thatthinginswift.com/debug-long-compile-times-swift/
As you can see, if you don't declare type of your variable that might impact build performance A LOT.
Disclaimer: I am pretty much a novice to Swift so prepare to cringe.
I have a series of arrays set out, when a user taps a button I would like one of these arrays to be called so I can use it in a function. They are named with thisArray then a number, i.e: thisArray1, thisArray2, etc.
I cannot find a way to make this work, the closest I have come to what I want is shown below but as you can all tell this definitely does not work.
var currentArray = "thisArray" + selectedArrayNumber
The outcome of this is to use the variable like below:
button1.setTitle(currentArray[1], for .normal)
If any of you can shed some light on this situation and tell me how badly I have gone wrong that would be much appreciated.
Create an array of your arrays, and then retrieve it using the selectedArrayNumber.
let arrays = [thisArray1, thisArray2, etc]
let currentArray = arrays[selectedArrayNumber]
If I have an array with elements linked to xassets with names like "card1", "card2", etc up to "card100" is there a quicker way to write these elements in the array format without having to write out all 100?
Also if this has been answered already please let me know or link to it. About 2 days into trying to teach myself to program.
Not exactly sure what you're asking but you may want to look at loops - Swift Loops. You can add items to an array in a for loop from 1 to 100.
Is this what you are looking for ?
let cards = Array(1...100).map({"card\($0)"})
This question already has answers here:
How to copy end of the Array in swift?
(6 answers)
Closed 6 years ago.
Swift's implementation of arrays is throwing me for a loop again! (Haw, haw.) All I want is to take an array of arbitrary length and get a new array (or an array slice) from it that has the first element removed.
Why is this so hard?
I just want to be able to do something like this:
let suffix = someArray.suffixFrom(1)
But I can't figure out how to do this. It seems the closest method I've found requires knowing the length of the array, which I don't know because it's computed inline and I really really hate having to split such a simple concept up into a bunch of variables and lines.
Elaboration:
I have a string split by colons (:) and I just want to create a Set containing all the :-delimited components excluding the first one.
So that a string "one:two:three" would return a set containing ["two", "three"]. Since I can create a Set from an array, all I really need is to get the suffix of the array, but I don't know how many components there are because it's inline:
return Set(attributeName?.componentsSeparatedByString(":").suffixFrom(1))
Why does Swift make this so hard?
Edit: Before a bunch of you suggest it, I'm well aware I could extend the array class to do this myself, but I'm writing a framework and I don't want to do that, and I also don't want to have to write a bloody utility function to do something so darned simple.
The CollectionType.dropFirst(_:) does exactly what you need, with the exact syntax you're looking for.
let suffix = someArray.dropFirst(1)
I do realize similar questions have been asked before, I looked at them before seeking help. But they were either not in Swift or too complex for me to decipher. My question is different from How do I shuffle an array in Swift? in that I have already done some of the work, like shuffling. The title was actually different from the question asked, which was "How do I randomize or shuffle the elements within an array in Swift?" I am only interested in iterating the resulting array and I couldn't separate that part from the rest of the code in the answers given for a question that encompassed so much more. That said, there are some great suggestions on that page so I think people like me will benefit from having both pages available. Maybe someone can set up a reciprocal link on that page as I have done here.
Admittedly, I am new to Swift and not a seasoned programmer in any language, but please don't assume I am coming here seeking help without trying to figure it out on my own. I am spending many hours learning the fundamentals of all C based languages and reading the Swift literature at developer.apple.com.
So the question will be more obvious, I and attempting to build the card game War. Thus far I have accomplished constructing the (an array) deck of cards and randomized it (shuffled). I am stuck at looping through the resulting array of 52 objects and assigning (moving) them to the two players hands (two new arrays). I'm not sure how much of my code I should display in order to help me but if you need more, I'll gladly provide it. Please note that this is only an exercise, practice for me to learn how to write complex programs, and some code, like the function to randomize, is not mine, I found it right here at stackoverflow. I'd almost prefer if you didn't just hand me the code that will work, I'm not likely going to learn as much that way, but if providing steps in plain English so I can figure out the syntax is too much trouble, so be it, provide an example, I'm sure I'll get plenty of chances to write/use the syntax later.
One more note, I'm only working in a playground at the moment, when and if I can get all the code working, I'll move to the UI stuff.
Thanks in advance, Rick
/* Skipping past everything I did to get here,
the array (shuffledDeck) has 52 shuffled cards (elements) in it.
The array is NSMutableArray and contains strings like
2Hearts, 5Spades, 14Clubs, etc. Each suit has 14 cards.*/
shuffledDeck
// create vars to hold shuffled hands
var playerOneHand = []
var playerTwoHand = []
/* Started a for loop to assign cards to each hand
but don't know which method(s) is/are best to use
to remove the first or last card and alternately
append (move) it to the (hopefully) initialized
variables playerOneHand and PlayerTwoHand.
Optionally, since the cards are already shuffled,
I could just split the deck using the range method,
whichever is easier. I tried and failed at both ways.*/
var i = 0
for dealtCard in shuffledDeck {
}
var shuffledDeck:[String] = ["2Hearts", "5Spades", "14Clubs", "etc"]
//shuffledDeck will of course be your shuffled deck
var playerOneHand:[String] = []
var playerTwoHand:[String] = []
for (index, cardString) in enumerate(shuffledDeck) {
if index % 2 == 0 {
playerOneHand.append(cardString)
}else{
playerTwoHand.append(cardString)
}
}
I’m looping through every item in the shuffledDeck, but with that I use the index of the array to get a number. I use this number to see if that number devided by 2 is equal to 0 (the number is even) or not (uneven) if a number is even, I get the item that is in the array at the given index and add that item to the hand of player one. If the index is uneven I add the item to the second player’s hand. This means the first item goed to player one’s hand, the second item goes to the hand of the second player. the third Item goes back to the first player and so on.
As mentioned by Martin R you can use the range method to assign the first half of the deck to the first player and the second to the second player as follow:
let cards:[String] = ["2♦️","3♦️","4♦️","5♦️","6♦️","7♦️","8♦️","9♦️","T♦️","J♦️","Q♦️","K♦️","A♦️","2♠️","3♠️","4♠️","5♠️","6♠️","7♠️","8♠️","9♠️","T♠️","J♠️","Q♠️","K♠️","A♠️","2♥️","3♥️","4♥️","5♥️","6♥️","7♥️","8♥️","9♥️","T♥️","J♥️","Q♥️","K♥️","A♥️","2♣️","3♣️","4♣️","5♣️","6♣️","7♣️","8♣️","9♣️","T♣️","J♣️","Q♣️","K♣️","A♣️"]
extension Array {
var shuffled:[T] {
var elements = self
for index in 0..<elements.count - 1 {
swap(&elements[index], &elements[Int(arc4random_uniform(UInt32(elements.count - 1 - index))) + index])
}
return elements
}
}
let cardsShuffled = cards.shuffled
let playerOneHand = cardsShuffled[0...25]
let playerTwoHand = cardsShuffled[26...51]
Note: The shuffle extension was created using this answer as reference