1. 清除字符串小數(shù)點(diǎn)末尾的0

代碼

import UIKit

extension String {
    /// 清除字符串小數(shù)點(diǎn)末尾的0
    func cleanDecimalPointZear() -> String {
        let newStr = self as NSString
        var s = NSString()
        
        var offset = newStr.length - 1
        while offset > 0 {
            s = newStr.substringWithRange(NSMakeRange(offset, 1))
            if s.isEqualToString("0") || s.isEqualToString(".") {
               offset -= 1
            } else {
                break
            }
        }
        return newStr.substringToIndex(offset + 1)
    }
}

2. 計算字符串的高度

主要通過以下兩個方法計算：
// String
func boundingRectWithSize(size: CGSize, options: NSStringDrawingOptions, attributes: [NSObject : AnyObject]!, context: NSStringDrawingContext!) -> CGRect
第一個參數(shù)是傳入一個CGSize結(jié)構(gòu)體;
第二個參數(shù)options是個配置選項(xiàng)
高度計算時就傳入NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading
如果你是用的String 的方法就有第三個參數(shù)：attributes其實(shí)就是NSAttributeString的屬性惑折，是個字典類型的對象，傳入你的字體
let attrs = [NSFontAttributeName : UIFont.systemFontOfSize(14)]
最后一個參數(shù)就穿nil 就好了
// 例子
let rowHeight: CGFloat = str.boundingRectWithSize(maxSize, options: NSStringDrawingOptions.UsesLineFragmentOrigin, attributes: [NSFontAttributeName : UIFont.systemFontOfSize(14)], context: nil).size.height + 14

// NSAttributedString
func boundingRectWithSize(size: CGSize, options: NSStringDrawingOptions, context: NSStringDrawingContext?) -> CGRect
注意：如果是計算NSMutableAttributedString揽碘，必須設(shè)置富文本的字體樣式辫诅，才可以計算正確

代碼

extension String {
    func heightWithConstrainedWidth(width: CGFloat, font: UIFont) -> CGFloat {
        let constraintRect = CGSize(width: width, height: CGFloat.max)
        let boundingBox = self.boundingRectWithSize(constraintRect, options: NSStringDrawingOptions.UsesLineFragmentOrigin, attributes: [NSFontAttributeName: font], context: nil)
        return boundingBox.height
    }
}

extension NSAttributedString {
func heightWithConstrainedWidth(width: CGFloat) -> CGFloat {
    let constraintRect = CGSize(width: width, height: CGFloat.max)
    let boundingBox = self.boundingRectWithSize(constraintRect, options: NSStringDrawingOptions.UsesLineFragmentOrigin, context: nil)
    return ceil(boundingBox.height)
  }
}