在UITextView或UILabel扩展中，添加这个函数:

我添加了一些代码来保持当前的带属性文本，如果您已经在视图中使用带属性字符串(而不是覆盖它们)。

func setLineHeight(_ lineHeight: CGFloat) {
    guard let text = self.text, let font = self.font else { return }

    let paragraphStyle = NSMutableParagraphStyle()
    paragraphStyle.lineSpacing = 1.0
    paragraphStyle.lineHeightMultiple = lineHeight
    paragraphStyle.alignment = self.textAlignment

    var attrString:NSMutableAttributedString
    if let attributed = self.attributedText {
        attrString = NSMutableAttributedString(attributedString: attributed)
    } else {
        attrString = NSMutableAttributedString(string: text)
        attrString.addAttribute(NSFontAttributeName, value: font, range: NSMakeRange(0, attrString.length))
    }
    attrString.addAttribute(NSParagraphStyleAttributeName, value:paragraphStyle, range:NSMakeRange(0, attrString.length))
    self.attributedText = attrString
}

SWIFT 3有用的扩展设置行间的空间更容易:)

extension UILabel
{
    func setLineHeight(lineHeight: CGFloat)
    {
        let text = self.text
        if let text = text 
        {

            let attributeString = NSMutableAttributedString(string: text)
            let style = NSMutableParagraphStyle()

           style.lineSpacing = lineHeight
           attributeString.addAttribute(NSParagraphStyleAttributeName,
                                        value: style,
                                        range: NSMakeRange(0, text.characters.count))

           self.attributedText = attributeString
        }
    }
}

根据@Mike的回答，减少lineHeightMultiple是关键点。下面的例子，它很适合我:

NSString* text = label.text;
CGFloat textWidth = [text sizeWithAttributes:@{NSFontAttributeName: label.font}].width;
if (textWidth > label.frame.size.width) {
  NSMutableParagraphStyle *paragraph = [[NSMutableParagraphStyle alloc] init];
  paragraph.alignment = NSTextAlignmentCenter;
  paragraph.lineSpacing = 1.0f;
  paragraph.lineHeightMultiple = 0.75;     // Reduce this value !!!
  NSMutableAttributedString* attrText = [[NSMutableAttributedString alloc] initWithString:text];
  [attrText addAttribute:NSParagraphStyleAttributeName value:paragraph range:NSMakeRange(0, text.length)];
  label.attributedText = attrText;
}

下面是UILabel的一个子类，它设置lineHeightMultiple并确保内在高度足够大，不会截断文本。

@IBDesignable
class Label: UILabel {
    override var intrinsicContentSize: CGSize {
        var size = super.intrinsicContentSize
        let padding = (1.0 - lineHeightMultiple) * font.pointSize
        size.height += padding
        return size
    }

    override var text: String? {
        didSet {
            updateAttributedText()
        }
    }

    @IBInspectable var lineHeightMultiple: CGFloat = 1.0 {
        didSet {
            updateAttributedText()
        }
    }

    private func updateAttributedText() {
        let paragraphStyle = NSMutableParagraphStyle()
        paragraphStyle.lineHeightMultiple = lineHeightMultiple
        attributedText = NSAttributedString(string: text ?? "", attributes: [
            .font: font,
            .paragraphStyle: paragraphStyle,
            .foregroundColor: textColor
        ])
        invalidateIntrinsicContentSize()
    }
}

在ios6中有另一个答案，那就是在标签上设置attributedText，使用NSAttributedString和适当的段落样式。关于NSAttributedString的行高，请参阅堆栈溢出答案:

NSAttributedString行高，对吗?

这应该会有帮助。然后你可以将你的标签分配给故事板中的这个自定义类，并直接在属性中使用它的参数:

open class SpacingLabel : UILabel {

    @IBInspectable open var lineHeight:CGFloat = 1 {
        didSet {
            let paragraphStyle = NSMutableParagraphStyle()
            paragraphStyle.lineSpacing = 1.0
            paragraphStyle.lineHeightMultiple = self.lineHeight
            paragraphStyle.alignment = self.textAlignment

            let attrString = NSMutableAttributedString(string: self.text!)
            attrString.addAttribute(NSAttributedStringKey.font, value: self.font, range: NSMakeRange(0, attrString.length))
            attrString.addAttribute(NSAttributedStringKey.paragraphStyle, value:paragraphStyle, range:NSMakeRange(0, attrString.length))
            self.attributedText = attrString
        }
    } 
}