Replace substring of NSAttributedString with another NSAttributedString

I want to replace a substring (e.g. @"replace") of an NSAttributedString with another NSAttributedString.

I am looking for an equivalent method to NSString's stringByReplacingOccurrencesOfString:withString: for NSAttributedString.

1. Convert your attributed string into an instance of NSMutableAttributedString.

2. The mutable attributed string has a mutableString property. According to the documentation:

   > "The receiver tracks changes to this string and keeps its attribute mappings up to date."

   So you can use the resulting mutable string to execute the replacement with replaceOccurrencesOfString:withString:options:range:.

Here is how you can change the string of NSMutableAttributedString, while preserving its attributes:

Swift:

// first we create a mutable copy of attributed text 
let originalAttributedText = nameLabel.attributedText?.mutableCopy() as! NSMutableAttributedString

// then we replace text so easily
let newAttributedText = originalAttributedText.mutableString.setString("new text to replace")

Objective-C:

NSMutableAttributedString *newAttrStr = [attribtedTxt.mutableString setString:@"new string"];

In my case, the following way was the only (tested on iOS9):

NSAttributedString *attributedString = ...;
NSAttributedString *anotherAttributedString = ...; //the string which will replace
    
while ([attributedString.mutableString containsString:@"replace"]) {
        NSRange range = [attributedString.mutableString rangeOfString:@"replace"];
        [attributedString replaceCharactersInRange:range  withAttributedString:anotherAttributedString];
    }

Of course it will be nice to find another better way.

Swift 4: Updated sunkas excellent solution to Swift 4 and wrapped in "extension". Just clip this into your ViewController (outside the class) and use it.

extension NSAttributedString {
    func stringWithString(stringToReplace: String, replacedWithString newStringPart: String) -> NSMutableAttributedString
    {
        let mutableAttributedString = mutableCopy() as! NSMutableAttributedString
        let mutableString = mutableAttributedString.mutableString
        while mutableString.contains(stringToReplace) {
            let rangeOfStringToBeReplaced = mutableString.range(of: stringToReplace)
            mutableAttributedString.replaceCharacters(in: rangeOfStringToBeReplaced, with: newStringPart)
        }
        return mutableAttributedString
    }
}

With Swift 4 and iOS 11, you can use one of the 2 following ways in order to solve your problem.

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#1. Using NSMutableAttributedString replaceCharacters(in:with:) method

NSMutableAttributedString has a method called replaceCharacters(in:with:). replaceCharacters(in:with:) has the following declaration:

>Replaces the characters and attributes in a given range with the characters and attributes of the given attributed string.

func replaceCharacters(in range: NSRange, with attrString: NSAttributedString)

The Playground code below shows how to use replaceCharacters(in:with:) in order to replace a substring of an NSMutableAttributedString instance with a new NSMutableAttributedString instance:

import UIKit

// Set initial attributed string
let initialString = "This is the initial string"
let attributes = [NSAttributedStringKey.foregroundColor : UIColor.red]
let mutableAttributedString = NSMutableAttributedString(string: initialString, attributes: attributes)

// Set new attributed string
let newString = "new"
let newAttributes = [NSAttributedStringKey.underlineStyle : NSUnderlineStyle.styleSingle.rawValue]
let newAttributedString = NSMutableAttributedString(string: newString, attributes: newAttributes)

// Get range of text to replace
guard let range = mutableAttributedString.string.range(of: "initial") else { exit(0) }
let nsRange = NSRange(range, in: mutableAttributedString.string)

// Replace content in range with the new content
mutableAttributedString.replaceCharacters(in: nsRange, with: newAttributedString)

---

#2. Using NSMutableString replaceOccurrences(of:with:options:range:) method

NSMutableString has a method called replaceOccurrences(of:with:options:range:). replaceOccurrences(of:with:options:range:) has the following declaration:

>Replaces all occurrences of a given string in a given range with another given string, returning the number of replacements.

func replaceOccurrences(of target: String, with replacement: String, options: NSString.CompareOptions = [], range searchRange: NSRange) -> Int

The Playground code below shows how to use replaceOccurrences(of:with:options:range:) in order to replace a substring of an NSMutableAttributedString instance with a new NSMutableAttributedString instance:

import UIKit

// Set initial attributed string
let initialString = "This is the initial string"
let attributes = [NSAttributedStringKey.foregroundColor : UIColor.red]
let mutableAttributedString = NSMutableAttributedString(string: initialString, attributes: attributes)

// Set new string
let newString = "new"

// Replace replaceable content in mutableAttributedString with new content
let totalRange = NSRange(location: 0, length: mutableAttributedString.string.count)
_ = mutableAttributedString.mutableString.replaceOccurrences(of: "initial", with: newString, options: [], range: totalRange)

// Get range of text that requires new attributes
guard let range = mutableAttributedString.string.range(of: newString) else { exit(0) }
let nsRange = NSRange(range, in: mutableAttributedString.string)

// Apply new attributes to the text matching the range
let newAttributes = [NSAttributedStringKey.underlineStyle : NSUnderlineStyle.styleSingle.rawValue]
mutableAttributedString.setAttributes(newAttributes, range: nsRange)

I had to bold text in <b> tags, here what I've done:

- (NSAttributedString *)boldString:(NSString *)string {
    UIFont *boldFont = [UIFont boldSystemFontOfSize:14];
    NSMutableAttributedString *attributedDescription = [[NSMutableAttributedString alloc] initWithString:string];

    NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@".*?<b>(.*?)<\\/b>.*?" options:NSRegularExpressionCaseInsensitive error:NULL];
    NSArray *myArray = [regex matchesInString:string options:0 range:NSMakeRange(0, string.length)] ;
    for (NSTextCheckingResult *match in myArray) {
        NSRange matchRange = [match rangeAtIndex:1];
        [attributedDescription addAttribute:NSFontAttributeName value:boldFont range:matchRange];
    }
    while ([attributedDescription.string containsString:@"<b>"] || [attributedDescription.string containsString:@"</b>"]) {
        NSRange rangeOfTag = [attributedDescription.string rangeOfString:@"<b>"];
        [attributedDescription replaceCharactersInRange:rangeOfTag withString:@""];
        rangeOfTag = [attributedDescription.string rangeOfString:@"</b>"];
        [attributedDescription replaceCharactersInRange:rangeOfTag withString:@""];
    }
    return attributedDescription;
}

NSMutableAttributedString *result = [[NSMutableAttributedString alloc] initWithString:@"I am a boy."];
[result addAttribute:NSForegroundColorAttributeName value:[UIColor blackColor] range:NSMakeRange(0, [result length])];

NSMutableAttributedString *replace = [[NSMutableAttributedString alloc] initWithString:@"a"];
[replace addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:NSMakeRange(0, [replace length])];

[result replaceCharactersInRange:NSMakeRange(5, [replace length]) withAttributedString:replace];

I find that all of the other answers does not work. Here is how I replaced content of a NSAttributed string in a category extension:

func stringWithString(stringToReplace:String, replacedWithString newStringPart:String) -> NSMutableAttributedString
{
    let mutableAttributedString = mutableCopy() as! NSMutableAttributedString
    let mutableString = mutableAttributedString.mutableString
    
    while mutableString.containsString(stringToReplace) {
        let rangeOfStringToBeReplaced = mutableString.rangeOfString(stringToReplace)
        mutableAttributedString.replaceCharactersInRange(rangeOfStringToBeReplaced, withString: newStringPart)
    }
    return mutableAttributedString
}

I have a specific requirement and fixed like below. This might help someone.

Requirement: In the storyboard, rich text directly added to UITextView's attribute which contains a word "App Version: 1.0". Now I have to dynamise the version number by reading it from info plist.

Solution: Deleted version number 1.0 from the storyboard, just kept "App Version:" and added below code.

NSAttributedString *attribute = self.firsttextView.attributedText;
NSMutableAttributedString *mutableAttri = [[NSMutableAttributedString alloc] initWithAttributedString:attribute];
NSString *appVersionText = @"App Version:";
if ([[mutableAttri mutableString] containsString:appVersionText]) {
    NSDictionary* infoDict = [[NSBundle mainBundle] infoDictionary];
    NSString* version = [infoDict objectForKey:@"CFBundleShortVersionString"];
    NSString *newappversion = [NSString stringWithFormat:@"%@ %@",appVersionText,version] ;
    [[mutableAttri mutableString] replaceOccurrencesOfString:appVersionText withString:newappversion options:NSCaseInsensitiveSearch range:NSMakeRange(0, mutableAttri.length)];
    self.firsttextView.attributedText = mutableAttri;
}

Done!! Updated/modified attributedText.

i created a Swift 5 extension for that

extension NSMutableAttributedString {
    
    func replace(_ findString: String, with replacement: String, attributes: [NSAttributedString.Key : Any]) {
        
        let ms = mutableString
        
        var range = ms.range(of: findString)
        while range.location != NSNotFound {
            addAttributes(attributes, range: range)
            ms.replaceCharacters(in: range, with: replacement)
            
            range = ms.range(of: findString)
        }
        
    }

}

use case

attributedString.replace("%EMAIL%", with: email, attributes: [.font:boldFont])