How to split string swift

In the previous exercise, Solved tasks for Swift lesson 8, we’ve practiced our knowledge from previous lessons.

In today’s Swift tutorial, we’re going to explain other String methods that I have intentionally kept from you because we didn’t know that strings are similar to arrays

When you create an arbitrary variable and write a dot after it, XCode will show us all of the available methods and variables, that we can call on that variable (we’ll go deeper into this in the OOP course). Let’s try it out:

The same suggestion can also be accessed by pressing Ctrl + Spacebar when the text cursor is on the dot. Of course, this applies to all variables and classes (we’ll use it further along the way, as well). The methods are ordered alphabetically and we can list them using the arrow keys. Xcode shows us the description of the methods, what they do, and what parameters do they need.

Let’s talk about the following methods and demonstrate them on simple examples:

Additional String methods

insert()

Inserts a substring into the string at a specific position. The parameters are the position in the string and the substring.

remove() and removeSubrange()

The remove() method is very simple, but it can only remove one character at a given index. Again, the index must be specified as the String.Index data type we have already encountered. removeSubrange() removes a substring from our string, but again, we need to pass it String.Index via the Range data type which makes it more complicated.

And a removeSubrange() example:

Note that in Range we need to use the (less than) operator, otherwise endIndex would make us overflow one position outside of the String via and the program would crash.

Substring()

Let’s try another example:

And the last one:

compare()

Now let’s look at 2 more, very useful, String methods.

split() and joined()

The joined() method, on the other hand, merges an array of substrings using a separator into a single string. The parameter is the separator. The output of the method is the resulting string. The method can be also called without a parameter, thus joining strings without separators.

Right then, let’s see what we’ve got up until now. We still don’t know how to declare objects, users, or even work with multidimensional arrays, i.e. matrices. Nevertheless, we want to make something cool, so we’ll settle with making a Morse code message decoder.

Morse code decoder

We’ll start out by preparing the program structure, as always. We need two strings for the messages, one for a message in Morse code, the other one will be empty for now and we’ll store the results of our efforts there. Next, we need letter definitions (as we had with vowels). Of course, we’ll also need the Morse code versions of the letter definitions. We’ll use arrays for both definitions this time since Morse letters consist of multiple text characters.

The structure of our program should now look something like this:

Why we defined the alphabet as an array too? It’ll save us a lot of effort when searching for a character by the Morse character representation. Otherwise, we’d have to deal with conversion of an Array.Index to a String.Index and the code would be much longer.

We could also add other Morse characters such as numbers and punctuation marks, but we won’t worry about them for now. We’ll split the String s with the split() method into an array of substrings containing the Morse characters. We’ll split it by the space character. Then we’ll iterate over the array using a for in loop:

Ideally, we should somehow deal with cases when the user enters e.g. multiple spaces between characters (users often do things of the sort). In this case, split() creates one more empty substring in the array. We should then detect it in the loop and ignore it, but we won’t deal with that in this lesson.

In the loop, we’ll attempt to find the current Morse character in the morseChars array. We’ll be interested in its index because when we look at that same index in the alphabetChars array, there will be the corresponding letter. This is mainly because both the arrays contain the same characters which are ordered alphabetically. Let’s place the following code into the loop’s body:

Now, we’ll print the message:

Done! If you want to train some more, you can create a program which would encode a string to the Morse code. The code would be very similar. We’ll use the split() and joined() methods several more times throughout our Swift courses.

Special characters and escaping

Let’s test them out:

The «\» character indicates a special character sequence in a string and can be used also e.g. to write Unicode characters as \u where xxxx is the character code.

The problem might be when we want to write \ itself, in this case we’ve to escape it by writing one more \ :

We can escape a quotation mark in the same way, so Swift wouldn’t misinterpret it as the end of the string:

Today we basically finished the on-line course on the Swift basic constructs.

In the following exercise, Solved tasks for Swift lesson 9, we’re gonna practice our knowledge from previous lessons.

How to split a string into an array of substrings in Swift

There are different ways to split a string into an array of substrings.

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Split by a string

You can use components(separatedBy:) method to divide a string into substrings by specifying string separator.

The result components look like this:

The above will produces the array:

Split by a set of characters

Split by a character

The above example will produce the following array of Substring:

maxSplits
The maximum number of times to split the collection, or one less than the number of subsequences to return. If maxSplits + 1 subsequences are returned, the last one is a suffix of the original collection containing the remaining elements. maxSplits must be greater than or equal to zero. The default value is Int.max.

The split(separator:maxSplits:omittingEmptySubsequences:) method return an array of Substring. When you finish the operation, you should convert it to a String by using the String(_:) initializer.

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How to Split a String — Swift 3.0

The following error kept showing up while I tried to split a string by iterating through it using a for-in loop:

Though this error informed me that, unlike arrays, strings can’t be split using a for-in loop, it did not provide guidance on how to fix the error. Naturally, I sought help from Stackoverflow. Below you will find the fruits of my search: two ways to split a string….

Option 2: Use components(separatedBy:) to create an array containing each word within the string that you would like to split. In the example below, each word within the string is separated into an array that you can then iterate through using a for-in loop.

This option is useful when the goal is to change each item (or in this case, word) within the string in the same manner. For instance, in the example below I used components(separatedBy:) to change each word within the stringOfWordsArray into Pig Latin. I did not want each character to change, but rather I wanted each word to be altered in the same way during each iteration (move the first letter of the original word to the end of the word and add “ay”).

Helpful links below….

Strings and Characters Overview — Apple’s The Swift Programming Language (Swift 3)

How to split a string by new lines in Swift

I have a string that I got from a text file.

I want to convert it to an array, one array element per line.

Depending on how the file was saved, the string could take one of the following forms:

string = «Line 1\nLine 2\nLine 3\n. » where \n is the new line (line feed) character

string = «Line 1\r\nLine 2\r\nLine 3\r\n. » where \r is the carriage return character.

As I understand it, \n is commonly used in Apple/Linux today, while \r\n is used in Windows.

How do I split a string at any line break to get a String array without any empty elements?

Update

There are several solutions that work below. At this point I don’t have any compelling reason to choose one as more correct than the others. Some factors that may influence choice could be (1) how «Swift» it is and (2) how fast it is for very long strings. You can provide feedback by upvoting one or more of them and/or leaving a comment.

See my summarized answer here

9 Answers 9

Trending sort

Trending sort is based off of the default sorting method — by highest score — but it boosts votes that have happened recently, helping to surface more up-to-date answers.

It falls back to sorting by highest score if no posts are trending.

Switch to Trending sort

Swift 5.2 or later

You can split your String using the new Character property isNewline :

You can also extend StringProtocol and create a lines instance property to break up the string lines into subsequences:

Original Answer

You can use String method enumerateLines:

Enumerates all the lines in a string.

Swift 3 or later

in Xcode 8.2, Swift 3.0.1:

Use NSString method components(separatedBy:)

Or use String method enumerateLines, like Leo Dabus ‘s answer

In Swift 2, the top-level split function is now a method on CollectionType (which each of String s «character views» conforms to). There are two versions of the method, you want the one that takes a closure as a predicate to indicate whether a given element should be treated as a separator.

So for a nice Swift-like way of doing this:

If you want to avoid NSCharacterSet altogether, you can just as easily split the collection of unicode compliant Character s.

How to split a string into substrings of equal length

If I make currentIndex = string.startIndex and then try to advance() it further than a string.endIndex, I get «fatal error: can not increment endIndex» before I check if my currentIndex Follow

10 Answers 10

Trending sort

Trending sort is based off of the default sorting method — by highest score — but it boosts votes that have happened recently, helping to surface more up-to-date answers.

It falls back to sorting by highest score if no posts are trending.

Switch to Trending sort

I just answered a similar question on SO and thought I can provide a more concise solution:

Swift 2

Swift 3

Swift 4

Changed to a while loop for better efficiency and made into a String’s extension by popular request:

Swift 5, based on @Ondrej Stocek solution

This problem could be easily solved with just one pass through the characters sequence:

Swift 2.2

Swift 3.0

Since String is a pretty complicated type, ranges and indexes could have different computational costs depending on the view. These details are still evolving, thus the above one-pass solution might be a safer choice.

Hope this helps

String extension based on «Code Different» answer:

Swift 3/4/5

Here is a string extension you can use if you want to split a String at a certain length, but also take into account words:

Swift 4:

This is a modification of Matteo Piombo‘s answer above.

My solution with an array of characters:

Or you can use more optimised variant for large strings with Substring:

You must not use range that exceeds the string size. The following method will demonstrates how to do it:

Usage:

endIndex is not a valid index; it is one more than the valid range.

Here is a version, that works in the following situations:

The solution with a while loop is actually a bit more flexible than the one with the stride. Here is a slight update (Swift 5) of Adam’s answer:

We can generalise it to take a an array of Ints instead of a single Int. So that we can split a string into substrings of various lengths like so:

Not the answer you’re looking for? Browse other questions tagged string swift swift2 or ask your own question.

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