是否有一种巧妙的方法将分数表示为属性字符串？

Question

我想知道是否有内置方法来表示

var someFraction = "1/12"

作为属性字符串？即"1"被抬起并压缩，而"12"被降低并被压缩。

感谢

Answer 1

如果要正确表示任意分数，则应分别为自定义UIFontDescriptor中的UIFontDescriptorFeatureSettingsAttribute设置org.hibernate.spatial.dialect.oracle.OracleSpatial10gDialect.properties和UIFontFeatureTypeIdentifierKey为UIFontFeatureSelectorIdentifierKey和kFractionsType。例如，你可以这样说：

kDiagonalFractionsSelector

具有以下结果：

您可以找到更多信息here

Swift 3.0

let label = UILabel(frame: CGRect(x: 0.0, y: 0.0, width: 1000.0, height: 100.0))
let pointSize : CGFloat = 60.0
let systemFontDesc = UIFont.systemFontOfSize(pointSize,
    weight: UIFontWeightLight).fontDescriptor()
let fractionFontDesc = systemFontDesc.fontDescriptorByAddingAttributes(
    [
        UIFontDescriptorFeatureSettingsAttribute: [
            [
                UIFontFeatureTypeIdentifierKey: kFractionsType,
                UIFontFeatureSelectorIdentifierKey: kDiagonalFractionsSelector,
            ], ]
    ] )
label.font = UIFont(descriptor: fractionFontDesc, size:pointSize)
label.text = "The Fraction is: 23/271"

Answer 2

您可以使用unicode显示分数而不是使用归因字符串。这个link有一个用目标C编写的源代码。您可以轻松地将其移植到swift中。

Answer 3

使用上面的UIFont扩展名：

static func fractionFont(forTextStyle textStyle: UIFontTextStyle) -> UIFont {

    let font = UIFont.preferredFont(forTextStyle: .title1)
    let descriptor = font.fontDescriptor.addingAttributes(
        [
            UIFontDescriptor.AttributeName.featureSettings: [
                [
                    UIFontDescriptor.FeatureKey.featureIdentifier: kFractionsType,
                    UIFontDescriptor.FeatureKey.typeIdentifier: kDiagonalFractionsSelector,
                    ],
            ]
        ] )

    return UIFont(descriptor: descriptor, size: font.pointSize)

}

然后在某处添加以下功能：

func fractionMutableAttributedString(for string: String) -> NSMutableAttributedString {

    let attributes: [NSAttributedStringKey: Any] = [.foregroundColor: UIColor.blue]
    let attributedText = NSMutableAttributedString(string: string, attributes: attributes)

    let substring = string.split(separator: " ") // Do we have a fractional value?
    if substring[1].contains("/") {
         let range = (string as NSString).range(of: String(substring[1]))
        attributedText.addAttribute(NSAttributedStringKey.font, value: UIFont.fractionFont(forTextStyle: .title1), range: range)
     }

     return attributedText

}

及其用途：

let string = "3 5/6"
label.attributedText = fractionMutableAttributedString(for: string)

产生正确的分数。