在设置attributedText后阻止自动UILabel字体更改

问题描述

我发现如果我将属性文本设置为 UILabel ，预定义字体将更改为属性文本的第一个字符的字体。例如：

I've figured out that if I set an attributed text to an UILabel, the predefined font will be changed to the font of the first character of attributed text. for example:

// the font size is set to 20 in Interface Builder
println(theLabel.font.pointSize);
var styledText = NSMutableAttributedString(string: "$100");
var smallFont = UIFont(name: theLabel.font.fontName, size: theLabel.font.pointSize / 2)!;
styledText.addAttribute(NSFontAttributeName, value: smallFont, range: NSMakeRange(0, 1));
theLabel.attributedText = styledText;
println(theLabel.font.pointSize);
// output:
// 20
// 10

我不知道它是否可以被称为错误，但在某些情况下它会导致问题。

I've no idea if it could be called a bug or not, but it causes problem in some cases.

任何人都可以建议一个干净的解决方案来获取默认字体在界面生成器中设置？

Can anybody suggest a clean solution to obtain the default font that have set in the Interface Builder?

将字体重置为预定义字体的一种解决方案是设置文本属性 UILabel ，因为这会导致 UILabel 切换到纯文本模式（不再有属性文本）。 / p>

One solution to reset the font to predefined font is to set the text property of UILabel, because that causes the UILabel to switch to the plain text mode (no attributed text anymore).

theLabel.text = ""; // reset the font
println(theLabel.font.pointSize);
// output:
// 20

推荐答案

假设让myLabel：UILabel 的字体大小为20. myLabel 应显示属性文本：foo bar，其中bar的字体大小为30。

Let say that let myLabel: UILabel have a font size of 20. myLabel should display an attributed text: "foo bar", where "bar" has font size of 30.

如果更改 myLabel 上的字体，打算更改字体大小 foo不是20，而是15，相反，你会发现这会导致你的 attributedText 搞砸了。

If you change the font on myLabel, with the intention to change the font size of "foo" to not be 20, but rather 15 instead, you will notice that this results in your attributedText being messed up.

受@ Majid调查结果的启发，如果在应用字体更改之前设置 text 属性。 attributedText 保持不变，现在更新为新的默认字体！

Inspired by @Majid's findings, if you set the text property before applying the font change. The attributedText stays intact, and now updated with a new "default" font!

func setFont(_ font: UIFont, keepAttributes: Bool = true) {
    // Store attributedText before it gets ruined by font change
    let attributed = attributedText
    if attributed != nil && keepAttributes {
        // This trick enables us to change "default" font for our attributedText.
        text = ""
    }
    // Apply font change
    self.font = font.font
    if keepAttributes {
        // Restore attribute text, now with a new `default` font
        attributedText = attributed
    }
}

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