效果图：
image
//实现富文本
var string:NSMutableAttributedString
string = NSMutableAttributedString(string:"北京")
//进行图文混排
var textAttachment:NSTextAttachment
textAttachment = NSTextAttachment()
textAttachment.image =UIImage(named:"f_flagdown02@2x")
textAttachment.bounds =CGRectMake(0,0,11,8);
var textAttachmentString:NSAttributedString
textAttachmentString = NSAttributedString(attachment: textAttachment)
//在城市名称后插入图片
string.insertAttributedString(textAttachmentString, atIndex: string.length)
//自定义导航左侧按钮
let btn =UIButton.init(type:UIButtonType.RoundedRect)
btn.frame =CGRectMake(0,0,70,30);
btn.backgroundColor =UIColor.redColor()
btn.addTarget(self, action:#selector(navBtnClick), forControlEvents: UIControlEvents.TouchUpInside)
let lbText:UILabel
lbText = UILabel()
lbText.frame =CGRectMake(0,0, btn.frame.size.width+10, btn.frame.size.height)
lbText.attributedText = string
lbText.textColor =UIColor.whiteColor()
lbText.font =UIFont.systemFontOfSize(13)
btn.addSubview(lbText)
btn.backgroundColor =UIColor.clearColor()
self.navigationItem.leftBarButtonItem =UIBarButtonItem.init(customView: btn)
