Swift 4 in Xcode 9 - 如何在 NSAttributedstring 中使用 boundingrect？

Question

我想获取UILabel中一些文本的长度，动态改变UILabel的宽度属性

但是我不知道如何在函数boundingrect中设置参数。这是Apple Developer的文档。

func boundingRect(with size: CGSize, 
      options: NSStringDrawingOptions = [], 
      context: NSStringDrawingContext?) -> CGRect

，我试过这样

let attr = NSMutableAttributedString(string: "test test test test , this is test text. test test test test , this is test text. test test test test , this is test text. ")
//attr.addattributes
print(attr.boundingrect(with: CGSize(width: CGFloat.greatestFiniteMagnitude, height: 0), option: .truncatesLastVisibleLine
,context: nil)!)

但最后我在打印时得到了错误的宽度，那么为什么以及如何得到正确的宽度。

Answer 1

使用

public extension NSAttributedString {
    public func width(height: CGFloat) -> CGFloat {
        let constraintRect = CGSize(width: .greatestFiniteMagnitude, height: height)
        let boundingBox = self.boundingRect(with: constraintRect,
                                            options: [.usesLineFragmentOrigin, .usesFontLeading],
                                            context: nil)
        return ceil(boundingBox.height)
    }
}

然后得到 let width = attr.width(height: height) 身高 > 0

Swift 4 in Xcode 9 - 如何在 NSAttributedstring 中使用 boundingrect？

Swift 4 in Xcode 9 - How to use boundingrect in NSAttributedstring?

nsattributedstring

ios

swift

swift4