- Swift 4 2d Array Example
- Swift 4 2d Array Tutorial
- Swift 4 2d Array Function
- Swift 4 Sort 2d Array
- Swift 4 2d Array C++
- Arrays help to store similar type of objects under a single variable name while providing access to the objects using an index. String Arrays store multiple strings under a single variable name. While getting started with String Arrays in Swift programming, let us see the syntax to create an empty array. Create an empty String Array.
- A series of Swift Tutorials that will cover all the basics of Apple's latest programming language - Swift 4! In part 6 we'll learn about arrays and the various functions we can perform with them.
During your programming adventures you might have stumbled upon the term Array a couple of times.
What is it and why is it important? To put it simply an Array is a collection of elements that is in an ordered series or arrangement.
It is important because it organizes and compiles data so that it can be easily managed and accessed. To better understand Arrays it is best to go back to the basics.
The basics
In Swift, we initialize a 2D array like this: var cinema = Int Actually, it's just an array of arrays. That means that each element of this array is an array too. Above, we have successfully declared a multidimensional array but filling it with zeros to be able to represent a cinema would be ineffective.
Suppose that we have to store data of 5 random samples of a product rating, in our normal way to do things we would probably go about by making 5 separate variables named rating1, rating2, rating3, etc.
This is clearly correct but isn’t it a bit cluttered? It also needs to have all 5 variables declared and may be hard to track in the future.
This is where Arrays come in, instead of the mess above we can simply write it as such:
Wasn’t that a lot easier and cleaner? There is a catch though, Array values can be extracted using indexes, and these indexes always start with 0 and not the usual 1.
A minor sacrifice if you ask me. How about we try printing our data? To do so just write it as
Following the same logic we can then treat our array as if its a normal Int variable like so
Of course like any other variable our array can also handle all data types but just remember that once you assign a data type to it then you should use it all throughout
It is also worth to note that we can also declare an empty array that can be done like so
Useful built-in functionalities
Checking and determining number of content
You can check if an array has no values by using isEmpty. Additionally, you can also check the number of content it has by using count
Accessing First and Last content of the array
You can check the first value of the array by using first. Conversely, you can also check the last value of the array by using last.
Subscript/Slice of the array
You can get a subscript/slice of an array by using the Range operator (…)
Adding and Removing elements to the array
Basic functionalities
You can add elements to the array by using append or insert([value], at: [index]). Conversely, you can also remove elements to the array by using remove(at: [index]).
Advanced functionalities
What is interesting to note is that different combinations that you can add and remove data these are
insert(contentsOf:[array], at: [index]) – Instead of just inserting a single value at a specified index we can insert a whole array or range of values inside as well.
insert(contentsOf:[array], at: [index]) – Instead of just inserting a single value at a specified index we can insert a whole array or range of values inside as well.
replaceSubrange([range from own array], with: [array] – We can also replace a whole range of values with another one.
append(contentsOf: [array]) – We can also add a range of values at the end of an array using
removeFirst() – is to remove the first value of the array
removeFirst([num]) – is to remove the first [num] of values from the array
Conversely you can also use
removeLast() – is to remove the last value of the array
removeLast([num]) – is to remove the last [num] of values from the array
removeSubrange([range]) – is to remove elements in a specified range
Checking for data inside the array
contains([element]) – is to check if the element/value is inside the array, returns a Bool
It can also be written as contains(where: [element])
min() – is to get the lowest value in the array. Note that if you compare strings it will get and compare the ASCII value of the letter/string
To check more into ASCII values you can check out this website http://www.asciitable.com/. In our case “A” is min because it has an ASCII value of 65, compared to a and b that has an ASCII value of 97 and 98 respectively.
max() – is to get the highest value in the array. Note that if you compare strings it will get and compare the ASCII value of the letter/string
Miscellaneous uses for data inside the array
sort() – sorts the value of the array. Note that if you compare strings it will get and compare the ASCII value of the letter/string
Swift 4 2d Array Example
You can also apply sort in descending using sort(by: > )
reverse() – it reverses the data inside the array
shuffle() – it shuffles the values of the array in a random order
randomElement() – it takes a random element in the array
forEach{ [element] -> Void } – iterates over the array and does specified commands to it
Swift 4 2d Array Tutorial
This can be written in another way by utilizing loops
And that’s it! Hope this information will serve you well to better understand and utilize Arrays in the future ?
Question or problem with Swift language programming:
Trying to understand how swift compares arrays.
Apple says there are optimisations behind the scene on array copies. Looks like sometimes – not always – structures are actually copied or not.
That said,
1) is iterating over all the array to perform a element-based comparison ? (looks like it)
-> How about performance / memory usage on very large arrays then ?
-> How about performance / memory usage on very large arrays then ?
2) Are we sure will ever return true if all elements are equal ? I have bad memories of on Java Strings
3) Is there a way to check if myArray1 and myArray2 are technically using the same “memory location” / pointer / etc. ? i’m after understanding how the optimisation works and potential caveats.
Thanks.
How to solve the problem:
Solution 1:
You’re right to be slightly nervous about :
Why? Swift arrays do not conform to
Equatable
, but they do have an operator, defined in the standard library as:This operator loops over the elements in
lhs
and rhs
, comparing the values at each position. It does not do a bitwise compare – it calls the operator on each pair of elements. That means if you write a custom for your element, it’ll get called.But it contains an optimization – if the underlying buffers for the two arrays are the same, it doesn’t bother, it just returns true (they contain identical elements, of course they’re equal!).
This issue is entirely the fault of the
NeverEqual
equality operator. Equality should be transitive, symmetric and reflexive, and this one isn’t reflexive (x x
is false). But it could still catch you unawares. Swift arrays are copy-on-write – so when you write
var x = y
it doesn’t actually make a copy of the array, it just points x
’s storage buffer pointer at y
’s. Only if x
or y
are mutated later does it then make a copy of the buffer, so that the unchanged variable is unaffected. This is critical for arrays to behave like value types but still be performant.In early versions of Swift, you actually could call on arrays (also in early versions, the mutating behaviour was a bit different, if you mutated
x
, y
would also change even though it had been declared with let
– which freaked people out so they changed it).You can kinda reproduce the old behaviour of on arrays with this (very implementation-dependent not to be relied-on except for poking and prodding investigations) trick:
Solution 2:
in Swift is the same as Java’s
equals()
, it compares values. in Swift is the same as Java’s , it compares references. Rules for dammit card game.
In Swift you can compare array content values as easy as this:
But this will not work if you want to compare references:
So the answers:
- I think the performance is optimal for doing value (not reference)
comparisons - Yes, if you want to compare values
- Swift arrays are value type and not reference type. So the memory
location is the same only if you compare it to itself (or use unsafe
pointers)
Solution 3:
For compare arrays of custom objects we can use elementsEqual.
Solution 4:
It depends on how do you want to compare. For example:
but
['1', '2'] ['1', '2'] // true
but
['1', '2'] ['2', '1'] // false
If you need that second case to also be true and are ok with ignoring repetitive values, you can do:
(use NSSet for Swift 2)
Set(['1', '2']) Set(['2', '1']) // true
(use NSSet for Swift 2)
Solution 5:
Swift 4 2d Array Function
Arrays conform to
Equatable
in Swift 4.1, negating the caveats mentioned in previous answers. This is available in Xcode 9.3.Swift 4 Sort 2d Array
Teechart pro vcl 2013 crack.
But just because they implemented did not mean Array or Optional conformed to Equatable. Since these types can store non-equatable types, we needed to be able to express that they are equatable only when storing an equatable type.
This meant these operators had a big limitation: they couldn’t be used two levels deep.
With conditional conformance, we can now fix this. It allows us to write that these types conform to Equatable—using the already-defined operator—if the types they are based on are equatable.
But just because they implemented did not mean Array or Optional conformed to Equatable. Since these types can store non-equatable types, we needed to be able to express that they are equatable only when storing an equatable type.
This meant these operators had a big limitation: they couldn’t be used two levels deep.
With conditional conformance, we can now fix this. It allows us to write that these types conform to Equatable—using the already-defined operator—if the types they are based on are equatable.