Replace substring of NSAttributedString with another NSAttributedString

Question

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

I am looking for a

Answer 1

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;
}

Answer 2

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
}

Answer 3

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)

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#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)