使用swift根据文本中的字符创建NSMutableAttributedString

Question

I have an array of labels for my buttons:

whenButtonArray = ["THURSDAY\nJUNE 5", "FRIDAY\nJUNE 6", "SATURDAY\nJUNE 7", "SUNDAY\nJUNE 8"]

What I'm trying to do is to use NSMutableAttributedString to make the text before the "\\n" be a bigger font than the text after it.

I initialized my string like this:

myMutableString = NSMutableAttributedString(string: whenWhereButtonArray[i], attributes: [NSFontAttributeName:UIFont(name: "Tungsten-Book", size: 22.0)!])

But how can I make the second part of the string (after the \\n) be a smaller font size? I know I can do something like this:

myMutableString.addAttribute(NSFontAttributeName, value: UIFont(name: "Tungsten-Book", size: 12.0)!, range: NSRange(location:3,length:4))

But I need the range to be dynamic based on the text for each button. Thanks!

Answer 1

As long as there are no Unicode character representations/emojis within your string the following should work. Otherwise it's best to work with NSString s as in rintaro's answer...

In order to update the location and length of the remaining string dynamically as needed for your sub attribute, you have to start by getting the position of "\\n" (I've used the formula from this answer.):

let range = whenWhereButtonArray[i].rangeOfString("\n")
let newlineIndex : Int = distance(whenWhereButtonArray[i].startIndex, range.startIndex)

Then knowing the beginning index of "\\n" you can calculate (1) the second string's index and then (2) the length of the second string. ex:

let secondStringIndex : Int = newlineIndex + countElements("\n")
let lengthOfSecondString : Int = countElements(whenWhereButtonArray[i]) - secondStringIndex

Then you can enter that info into the sub attribute formula like so:

myMutableString.addAttribute(NSFontAttributeName, value: UIFont(name: "Tungsten-Book", size: 12.0)!, range: NSRange(location:secondStringIndex,length:lengthOfSecondString))

Answer 2

In this case, working with NSString is relatively easier than working with Swift String :

let whenButtonArray = ["THURSDAY\nJUNE 5", "FRIDAY\nJUNE 6", "SATURDAY\nJUNE 7", "SUNDAY\nJUNE 8"]

let str = whenButtonArray[0] as NSString // cast to `NSString`
let attributed = NSMutableAttributedString(string: str, attributes: [NSFontAttributeName:UIFont(name: "Arial", size: 22.0)!])
let nl = str.rangeOfString("\n")
if nl.location != NSNotFound {
    let range = NSMakeRange(NSMaxRange(nl), str.length - NSMaxRange(nl))
    attributed.addAttribute(NSFontAttributeName, value: UIFont(name: "Arial", size: 12.0)!, range: range)
}