Swift：重构 NSMutableAttributedString

Question

I have used NSMutableAttributedString/NSAttributedString here and there but don't have extensive experience with them. I have a code block that repeats itself and was wondering how would I go about refactoring it? I've been working on a few extensions to refactor this but haven't had any luck.

The attributes goes into a UILabel variable closure.

let attributes = NSMutableAttributedString(string: "ID: \n",
                                               attributes: [NSAttributedString.Key.foregroundColor : UIColor.black,
                                                            NSAttributedString.Key.backgroundColor : UIColor.clear,
                                                            NSAttributedString.Key.font : UIFont(name: "Helvetica", size: 15)!])
    attributes.append(NSMutableAttributedString(string: "\(nameID)",
                                                attributes: [NSAttributedString.Key.foregroundColor : UIColor.white,
                                                             NSAttributedString.Key.backgroundColor : UIColor.customBlue(),
                                                             NSAttributedString.Key.font : UIFont(name: "Helvetica", size: 15)!]))
    attributes.append(NSMutableAttributedString(string: "\nDate Created: \n",
                                                attributes: [NSAttributedString.Key.foregroundColor : UIColor.black,
                                                             NSAttributedString.Key.backgroundColor : UIColor.clear,
                                                             NSAttributedString.Key.font : UIFont(name: "Helvetica", size: 15)!]))
    attributes.append(NSMutableAttributedString(string: "TEST",
                                                attributes: [NSAttributedString.Key.foregroundColor : UIColor.white,
                                                             NSAttributedString.Key.backgroundColor : UIColor.customBlue(),
                                                             NSAttributedString.Key.font : UIFont(name: "Helvetica", size: 15)!]))
    attributes.append(NSMutableAttributedString(string: "\nDate Last Used: \n",
                                                attributes: [NSAttributedString.Key.foregroundColor : UIColor.black,
                                                             NSAttributedString.Key.backgroundColor : UIColor.clear,
                                                             NSAttributedString.Key.font : UIFont(name: "Helvetica", size: 15)!]))
    attributes.append(NSMutableAttributedString(string: "TEST",
                                                attributes: [NSAttributedString.Key.foregroundColor : UIColor.white,
                                                             NSAttributedString.Key.backgroundColor : UIColor.customBlue(),
                                                             NSAttributedString.Key.font : UIFont(name: "Helvetica", size: 15)!]))

Answer 1

Try looking at your code and seeing if there's a pattern. What I see is creating multiple NSAttributedString s with String values, setting foreground and background, and the same font over and over. So this is ripe for the refactor picking.

First, set up your data:

// one note here is that you actually have a newline char for every entry, so it's probably better practice t simply drop them and apply them in your loop which we'll get to
let values = ["ID:", nameID /*I assume this is already a `String`*/, "Date Created: ", "TEST", "Date Last Used:", "Test"]

Colors seem to follow their own pattern: titles are black on clear and values are white on custom blue. We can use this in our loop, too. Let's set up our attributes so they're easy to reference:

let titleAttributes: [NSAttributedString.Key: Any] = [
  .foregroundColor: UIColor.black,
  .backgroundColor: UIColor.clear,
  .font: UIFont(name: "Helvetica", size: 15)!
]

let valueAttributes: [NSAttributedString.Key: Any] = [
  .foregroundColor: UIColor.white,
  .backgroundColor: UIColor.customBlue(),
  .font: UIFont(name: "Helvetica", size: 15)!
]

Now, let's loop:

let mutableString = NSMutableAttributedString()

for (index, currentValue) in values.enumerated() {
  // if we're on an even number, we have a title. If it's odd, it's a value
  let attributes = index % 2 == 0 ? titleAttributes : valueAttributes

  // if we aren't on the last index, add a newline to the value
  let value = index < values.count - 1 ? "\(currentValue)\n" : currentValue

  mutableString.appendAttributedString(string: value, attributes: attributes)
}