Is it possible to get a listing of attributes and

问题:

I've created a method that takes a NSAttributedString and I'm looking to dynamically create a subview and label to put the string into. Because attributes like font and size need to be determined to correctly determine the size of the label, I need to determine if it is possible to iterate through values and ranges that have been applied to the attributed string?

I understand that I could pass the attributes separately, but for sake of reusability, i'd like to be able to pass as few parameters to the method as possible.

回答1:

Apple expects you to use enumerateAttributesInRange:options:usingBlock:. The block you supply will receive ranges and the attributes applicable for that range.

I've used that in my code to create invisible buttons that are placed behind text so that it acts as a hyperlink.

You could also use enumerateAttribute:inRange:options:usingBlock: if there's only one you're interested in, but no halfway house is provided where you might be interested in, say, two attributes but not every attribute.

回答2:

Swift 5 – 4

let attributedText = NSAttributedString(string: "Hello, playground", attributes: [
  .foregroundColor: UIColor.red, 
  .backgroundColor: UIColor.green, 
  .ligature: 1, 
  .strikethroughStyle: 1
])

// retrieve attributes
let attributes = attributedText.attributes(at: 0, effectiveRange: nil)

// iterate each attribute
for attr in attributes {
  print(attr.key, attr.value)
}

---

In case, that you have defined attributedText of label.

Swift 3

var attributes = attributedText.attributes(
  at: 0, 
  longestEffectiveRange: nil, 
  in: NSRange(location: 0, length: attributedText.length))

Swift 2.2

var attributes = attributedText.attributesAtIndex(0,   
  longestEffectiveRange: nil, 
  inRange: NSMakeRange(0, attributedText.length))

回答3:

If you need all of the attributes from the string in the entire range, use this code:

NSDictionary *attributesFromString = [stringWithAttributes attributesAtIndex:0 longestEffectiveRange:nil inRange:NSMakeRange(0, stringWithAttributes.length)];

回答4:

Apple's Docs have a number of methods to access attributes:

To retrieve attribute values from either type of attributed string, use any of these methods:

attributesAtIndex:effectiveRange: attributesAtIndex:longestEffectiveRange:inRange: attribute:atIndex:effectiveRange: attribute:atIndex:longestEffectiveRange:inRange: fontAttributesInRange: rulerAttributesInRange:

回答5:

Swift 3:

// in case, that you have defined `attributedText` of label
var attributes = attributedText.attributes(at: 0, longestEffectiveRange: nil, in: NSMakeRange(0, attributedText.length))
...

回答6:

Swift 4:

If you want to get the attributes for NSTextAttachment (just change the attribute value if you want font)

commentTextView.attributedText.enumerateAttribute(NSAttachmentAttributeName,
                        in:NSMakeRange(0, commentTextView.attributedText.length),
                        options:.longestEffectiveRangeNotRequired) {
                        value, range, stop in
                            if let attachment = value as? NSTextAttachment {
                                print("GOT AN ATTACHMENT! for comment at \(indexPath.row)")
                            }
}

回答7:

I have modified one of the answers with suggested fixes to prevent infinite recursion and application crashes.

@IBDesignable
extension UITextField{

    @IBInspectable var placeHolderColor: UIColor? {
        get {
            if let color = self.attributedPlaceholder?.attribute(.foregroundColor, at: 0, effectiveRange: nil) as? UIColor {
                return color
            }
            return nil
        }
        set {
            self.attributedPlaceholder = NSAttributedString(string:self.placeholder != nil ? self.placeholder! : "", attributes:[.foregroundColor: newValue!])
        }
    }
}