Swift 寫九九乘法表

1. Nested for-loop 產生 100個 UILabel：

筆記： view.addSubview(label) 要寫在 inner loop

let width = view.frame.width / 10
        var x: CGFloat = 0
        for i in 0...9{
            print(x)
            var y: CGFloat = width
            for j in 0...9{
                let label = UILabel(frame: CGRect(x: x, y: y, width: width, height: width))
                if i == 0, j == 0 {
                    label.text = "X"
                    label.font = UIFont.boldSystemFont(ofSize: 17)
}else if i != 0, j == 0 {
                    label.text = "\(i)"
                    label.font = UIFont.boldSystemFont(ofSize: 17)
}else if i == 0, j != 0 {
                    label.text = "\(j)"
                    label.font = UIFont.boldSystemFont(ofSize: 17)
                }else if j == 9 || (i>1 && i<5 && i+j == 10) || (j >= 5 && i == j)  {
                    label.text = "\(j*i)"
                    label.backgroundColor = UIColor(
                        red:   .random(in: 0...1),
                        green: .random(in: 0...1),
                        blue:  .random(in: 0...1),
                        alpha: 1.0
                     )
                }else{
                    label.text = "\(j*i)"
                }
                view.addSubview(label)
                y = y + width*CGFloat(1)
        }
        x = x + width
    }

參考作品：

Swift 九九乘法App/Multiplication Table App

2. Nested for-loop 寫入String:

for i in 1...9{
      for j in 1...9{
           if i == 9 || (j > 1 && j<5 && i+j == 10) || (i >= 5 && i == j)  {
                    content += " " + "\(i*j)" + ""
                    content += "\t"
       }else{
                    content += " " + "🍎" + ""
                    content += "\t"
                }
            }
            content += "\n"
        }
        numberLabel.text = content
        numberLabel.textAlignment = .center
    
    }

由于只有一个Label， NSAttributedString 無法成功更換 String 裡以 if … esle 區隔的 backgroundColor。彼得潘提醒前一種作法方便更換個別 label 的backgroundColor 和 font。

因此，要将content 定義為NSMutableAttributedString屬性，同時創建string 。以for-loop 將一段段的string藉由append()拼接起來，最後放到content 裡。如此能以if vs else 分別設定不同的string 內容和attributes(String 的樣式)。完整思路和作法寫在下面文章中。

One UILabel with two NSMutableAttributedString

numberLabel.textAlignment = .center
        var content: NSMutableAttributedString = NSMutableAttributedString()
        for i in 1...9{
         for j in 1...9{
             let string: String
             let attributes: [NSMutableAttributedString.Key: Any]
             if i == 9 || (j > 1 && j<5 && i+j == 10) || (i >= 5 && i == j)  {
                 string = " \(i*j)\t"
                 attributes = [
                     .foregroundColor: UIColor.black,
                     .backgroundColor: UIColor(
                         red:   .random(in: 0...1),
                         green: .random(in: 0...1),
                         blue:  .random(in: 0...1),
                         alpha: 1.0
                      ),
                     .font: UIFont.boldSystemFont(ofSize: 17)
                 ]
             }else{
                 string = " \(i*j)\t"
                 attributes = [
                     //.kern: 5,
                     .foregroundColor: UIColor.black,
                     .backgroundColor: UIColor.white,
                     .font: UIFont.boldSystemFont(ofSize: 17)
                 ]
             }
             let attributedStringToAppend = NSMutableAttributedString(string: string, attributes: attributes)
             content.append(attributedStringToAppend)
         }
         content.append(NSAttributedString(string: "\n"))
     }
        numberLabel.attributedText = content
}

twber/multiplicationTable