Adding text to string

Question

I am styling some dynamic markdown, however the framework I am using for styling doesnt support nested tags for links.

I need to parse the string and close the styling markdown tags effectively this :

    "__Some bold text [FIRST LINK](https://FIRSTLINK.COM \"FIRST LINK\"), more bold text.__\n\n additional text \n\n
 *some italic text[SECOND LINK](https://SECONDLINK.COM) ending text,*"

to this:

    "__Some bold text __[FIRST LINK](https://FIRSTLINK.COM \"FIRST LINK\")__, more bold text.__\n\n additional text \n\n
 *some italic text*[SECOND LINK](https://SECONDLINK.COM)* ending text,*"

This is only really going to be for bold and italic text. I started going down the route of

var str = "__Some bold text [FIRST LINK](https://FIRSTLINK.COM \"FIRST LINK\"), more bold text.__\n\n additional text \n\n *some italic text[SECOND LINK](https://SECONDLINK.COM) ending text,*"

    let bold = str.components(separatedBy: "__")
    for var string in bold {
        if let matchedIndex = string.index(of: "[") {
            string.insert(contentsOf: "__", at: matchedIndex)
        }
    }

But wondered, is there a better way to do this in Swift?

Edit - for clarity - essentially I need to modify the existing string to have closed tags prior to a link tag and re opened after a link tag - this prevents the links from being nested with the style tags and allows the styler framework to apply attributed strings accordingly

EDIT --- in line with @Linus comment here is the results of the regex (note running these out side of an extension in order to be able to test in a playground

var str = "__Some bold text [FIRST LINK](https://FIRSTLINK.COM \"FIRST LINK\"), more bold text.__\n additional text \n *some italic text[SECOND LINK](https://SECONDLINK.COM) ending text,*\n__sfdadhfjkh [THIRD LINK](https://THIRDLINK.COM \"THIRD LINK\"), more bold text.__"

do {
    var regex = try NSRegularExpression(pattern:  "(\\[.*?\\))" , options: [.caseInsensitive])
    var newString = regex.stringByReplacingMatches(in: str, options: [], range: NSMakeRange(0, str.utf16.count), withTemplate: "__$1__")
    print("\nFirst regex  __$1__  \n\n\(newString)")

    regex = try NSRegularExpression(pattern:  "(\\[.*?\\))" , options: [.caseInsensitive])
        var newerString = regex.stringByReplacingMatches(in: str, options: [], range: NSMakeRange(0, str.utf16.count), withTemplate: "*$1*")
        print("\nSecond Regex *$1* \n\n"+newerString)
} catch { print("ERROR: searchFor regex (\("(\\[.*?\\))")) on string (\(str)) failed") }

Printed results

First regex  __$1__  

__Some bold text __[FIRST LINK](https://FIRSTLINK.COM "FIRST LINK")__, more bold text.__
 additional text 
 *some italic text__[SECOND LINK](https://SECONDLINK.COM)__ ending text,*
__sfdadhfjkh __[THIRD LINK](https://THIRDLINK.COM "THIRD LINK")__, more bold text.__

Second Regex *$1* 

__Some bold text *[FIRST LINK](https://FIRSTLINK.COM "FIRST LINK")*, more bold text.__
 additional text 
 *some italic text*[SECOND LINK](https://SECONDLINK.COM)* ending text,*
__sfdadhfjkh *[THIRD LINK](https://THIRDLINK.COM "THIRD LINK")*, more bold text.__

I need to have both Italic and strong tags amended on the same string in order to pass it to a view to be styled

Your example doesn't work, right? I don't see anything that inserts the __ after the link's closing parenthesis. — NRitH
– NRitH, Commented Aug 6, 2018 at 17:17
@NRitH the example isn't complete as its just an indication of the route i was going to take.... — user499846
– user499846, Commented Aug 6, 2018 at 19:58

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

I'm using the following String extension that allows you to find strings that match a certain regex pattern and replace it with some other string:

extension String {
    mutating func replaceOccurrence(ofPattern pattern: String, with replacementString: String) {
        do {
            let regex = try NSRegularExpression(pattern: pattern, options: [.caseInsensitive])
            self = regex.stringByReplacingMatches(in: self, options: [], range: NSMakeRange(0, utf16.count), withTemplate: replacementString)
        } catch { print("ERROR: searchFor regex (\(pattern)) on string (\(self)) failed") }
    }
}

Then, you could replace (\[.*?\)) with __$1__, like this:

str.replaceOccurrence(ofPattern: "(\\[.*?\\))", with: "__$1__")

Explanation

...in case you're unfamiliar with regular expressions:

The regex:

( - opening parenthesis, that creates a new group which is later used to insert the matched string back into the replacement string
\[ - matches a bracket; needs to be escaped using \ to disable the bracket's regex meaning & match the actual character instead
.* - matches any character...
? - ...until...
\) - ...the next closing parenthesis; this one also needs to be escaped to match the actual character, and not create a new group
) - closes the group

The replacement:

__ - your replacement string: opening bold range in this case
$1 - inserts the previously matched group here __ - again, your replacement string: closing bold range in this case

Fun-Fact: in Swift, you need to escape escaping characters, like \\ to make sure the code compiles, because Xcode thinks, you're trying to escape a character from the string at compile-time.
That's why the regex isn't (\[.*?\)), but (\\[.*?\\)).

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Aug 6, 2018 at 17:27

LinusG.

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14 Comments

user499846 Over a year ago

Hey thanks @Linus - this looks really good - however there are a couple of issues. I ideally want to just amend the text in place rather than pulling out specific sections: for instance running the following : do { let regex = try NSRegularExpression(pattern: "(\[.*?\))" , options: [.caseInsensitive]) var newString = regex.stringByReplacingMatches(in: str, options: [], range: NSMakeRange(0, str.utf16.count), withTemplate: "$1") print("First regex (newString)") } catch { print("ERROR: searchFor regex (("(\[.*?\))")) on string ((str)) failed") }

user499846 Over a year ago

only returns First regex Some bold text _FIRST LINK, more bold text._

user499846 Over a year ago

Also I need to run the same for the italic - which changing the pattern to '"$1"' returns Some bold text FIRST LINK, more bold text.

user499846 Over a year ago

Sorry regex is something I have never mastered :(

LinusG. Over a year ago

No problem. I’m having a hard time to understand what you’re actually trying to do, as I apparently misunderstood it at least in some way. Can you please, in a clean and compact example, show what exactly you’re trying to do? @user499846

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