在输入文本字段时在文本字段字符之间添加空格

Question

我有一个textfield最大字符范围为16的字符，每4个字符后，我要添加一个负字符或空格，然后编写其余的字符，例如本示例5022-2222-2222-2222。有我的代码，但是那不起作用，该怎么办？

if textField.text?.characters.count  == 5 {

               let  l = textField.text?.characters.count
            let attributedString = NSMutableAttributedString(string: cartNumberTextField.text!)
            attributedString.addAttribute(NSKernAttributeName, value: CGFloat(4.0), range: NSRange(location: l!, length: 4))
            cartNumberTextField.attributedText = attributedString

            }

            else if textField.text?.characters.count  == 9 {

                let  l = textField.text?.characters.count
                let attributedString = NSMutableAttributedString(string: cartNumberTextField.text!)
                attributedString.addAttribute(NSKernAttributeName, value: CGFloat(4.0), range: NSRange(location: l!, length: 4))
                cartNumberTextField.attributedText = attributedString

            }

            else if textField.text?.characters.count  == 13 {

                let  l = textField.text?.characters.count
                let attributedString = NSMutableAttributedString(string: cartNumberTextField.text!)
                attributedString.addAttribute(NSKernAttributeName, value: CGFloat(4.0), range: NSRange(location: l!, length: 4))
                cartNumberTextField.attributedText = attributedString

            }

我在UITextField shouldChangeCharactersIn范围方法中添加此代码。

Answer 1

我们可以从实现oisdk：s SwiftSequence

chunk(n:)方法的（版本号）的Swift
3版本开始：Collection

/* Swift 3 version of Github use oisdk:s SwiftSequence's 'chunk' method:
   https://github.com/oisdk/SwiftSequence/blob/master/Sources/ChunkWindowSplit.swift */
extension Collection {
    public func chunk(n: IndexDistance) -> [SubSequence] {
        var res: [SubSequence] = []
        var i = startIndex
        var j: Index
        while i != endIndex {
            j = index(i, offsetBy: n, limitedBy: endIndex) ?? endIndex
            res.append(self[i..<j])
            i = j
        }
        return res
    }
}

在这种情况下，实现自定义格式是创建4个字符的块并将其通过“-”连接的简单情况：

func customStringFormatting(of str: String) -> String {
    return str.characters.chunk(n: 4)
        .map{ String($0) }.joined(separator: "-")
}

用法示例：

print(customStringFormatting(of: "5022222222222222")) // 5022-2222-2222-2222
print(customStringFormatting(of: "50222222222222"))   // 5022-2222-2222-22
print(customStringFormatting(of: "5022222"))          // 5022-222

如果适用于的textField(_:shouldChangeCharactersIn:replacementString:)方法UITextFieldDelegate，我们可能希望过滤掉customStringFormatting(of:)方法中的现有分隔符，并将其实现为String扩展：

extension String {
    func chunkFormatted(withChunkSize chunkSize: Int = 4, 
        withSeparator separator: Character = "-") -> String {
        return characters.filter { $0 != separator }.chunk(n: chunkSize)
            .map{ String($0) }.joined(separator: String(separator))
    }
}

并实现文本字段的受控更新，例如，如下所示：

let maxNumberOfCharacters = 16

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
    // only allow numerical characters
    guard string.characters.flatMap({ Int(String($0)) }).count ==
        string.characters.count else { return false }

    let text = textField.text ?? ""

    if string.characters.count == 0 {
        textField.text = String(text.characters.dropLast()).chunkFormatted()
    }
    else {
        let newText = String((text + string).characters
            .filter({ $0 != "-" }).prefix(maxNumberOfCharacters))
        textField.text = newText.chunkFormatted()
    }
    return false
}

上面的最后一部分将截断用户可能粘贴的字符串（假定它们都是数字的），例如

// current 
1234-1234-123

// user paste:
777777777
  /* ^^^^ will not be included due to truncation */

// will result in
1234-1234-1237-7777