Add highlight/background to only text using Swift - ios

Question

I want to highlight or add a background only on a text on a label that is not center-aligned.
I already tried Attributed Strings (https://stackoverflow.com/a/38069772/676822) and using regex but didn't get near a good solution.
NSAttributedString won't work because my label is not centered and it doesn't contain line breaks. It's just a long text that takes multiple lines.
This is what I'm trying to accomplish:
Note: It's not "Evangelizing\nDesign\nThinking" it's "Evangelizing Design Thinking"
Thanks!

Answer 1

As far as I have tried its not possible to get what you want simply with attributed text because using:
let attributedText = NSMutableAttributedString(string: "Evangelizing Desing Thinking",
attributes: [
.font: UIFont.systemFont(ofSize: 14),
.backgroundColor: UIColor.gray
]
)
Will add extray gray background at the end of each line. My previous answer was not good neither because it only adds a gray background on each word, not on spaces, and as #Alladinian noticed, ranges can be wrong in some cases.
So here is a hack you can use to achieve what you want. It uses multiple labels but it can be easily improved by putting labels in a custom view. So, in your viewDidLoad / CustomView function add:
// Maximum desired width for your text
let maxLabelWidth: CGFloat = 80
// Font you used
let font = UIFont.systemFont(ofSize: 14)
// Your text
let text = "Eva ngel izing Des ing a Thin king"
// Width of a space character
let spaceWidth = NSString(string: " ").size(withAttributes: [NSAttributedString.Key.font: font]).width
// Width of a row
var currentRowWidth: CGFloat = 0
// Content of a row
var currentRow = ""
// Previous label added (we keep it to add constraint betweeen labels)
var prevLabel: UILabel?
let subStrings = text.split(separator: " ")
for subString in subStrings {
let currentWord = String(subString)
let nsCurrentWord = NSString(string: currentWord)
// Width of the new word
let currentWordWidth = nsCurrentWord.size(withAttributes: [NSAttributedString.Key.font: font]).width
// Width of the row if you add a new word
let currentWidth = currentRow.count == 0 ? currentWordWidth : currentWordWidth + spaceWidth + currentRowWidth
if currentWidth <= maxLabelWidth { // The word can be added in the current row
currentRowWidth = currentWidth
currentRow += currentRow.count == 0 ? currentWord : " " + currentWord
} else { // Its not possible to add a new word in the current row, we create a label with the current row content
prevLabel = generateLabel(with: currentRow,
font: font,
prevLabel: prevLabel)
currentRowWidth = currentWordWidth
currentRow = currentWord
}
}
// Dont forget to add the last row
generateLabel(with: currentRow,
font: font,
prevLabel: prevLabel)
Then you have to create the generateLabel function:
#discardableResult func generateLabel(with text: String,
font: UIFont,
prevLabel: UILabel?) -> UILabel {
let leftPadding: CGFloat = 50 // Left padding of the label
let topPadding: CGFloat = 100 // Top padding of (first) label
let label = UILabel()
label.translatesAutoresizingMaskIntoConstraints = false
self.view.addSubview(label)
label.leftAnchor.constraint(equalTo: self.view.leftAnchor, constant: leftPadding).isActive = true
if let prevLabel = prevLabel {
label.topAnchor.constraint(equalTo: prevLabel.bottomAnchor).isActive = true
} else {
label.topAnchor.constraint(equalTo: self.view.topAnchor, constant: topPadding).isActive = true
}
label.font = font
label.text = text
label.backgroundColor = .gray
return label
}
Previous answer:
As Yogesh suggested, you can use attributed string:
// Init label
let label = UILabel(frame: CGRect(x: 50, y: 50, width: 90, height: 120))
self.view.addSubview(label)
label.lineBreakMode = .byTruncatingTail
label.numberOfLines = 0
label.backgroundColor = .white
// Create attributed text
let text = "Evangelizing Desing Thinking"
let attributedText = NSMutableAttributedString(string: text,
attributes: [
.font: UIFont.systemFont(ofSize: 14)
]
)
// Find ranges of each word
let subStrings = text.split(separator: " ")
let ranges = subStrings.map { (subString) -> Range<String.Index> in
guard let range = text.range(of: subString) else {
fatalError("something wrong with substring") // This case should not happen
}
return range
}
// Apply background color for each word
ranges.forEach { (range) in
let nsRange = NSRange(range, in: text)
attributedText.addAttribute(.backgroundColor, value: UIColor.gray, range: nsRange)
}
// Finally set attributed text
label.attributedText = attributedText