Swift中创建一个UIBarButtonItem的分类

1.新建文件创建分类

//
//  UIBarButtonItem+Category.swift


import UIKit

extension UIBarButtonItem{

    /**
     返回一个UIBarButtonItem

     - parameter imageName: 图片名称
     - parameter target:    目标
     - parameter action:    监听方法

     - returns: UIBarButtonItem
     */

    // 如果在func前面加上"class"，就相当于OC中的 + 
    class func createBarButtonItem(imageName:String, target:AnyObject, action:Selector) -> UIBarButtonItem{
        let btn = UIButton()
        btn.setImage(UIImage(named: imageName), forState: UIControlState.Normal)
        btn.setImage(UIImage(named: imageName + "_highlighted"), forState: UIControlState.Highlighted)
        btn.addTarget(target, action: action, forControlEvents: UIControlEvents.TouchUpInside)
        btn.sizeToFit()
        return UIBarButtonItem(customView: btn)
    }
}

2.使用这个分类

 /**
     初始化导航条
     */
    private func setupNav(){
        navigationItem.leftBarButtonItem = UIBarButtonItem.createBarButtonItem("navigationbar_friendattention",target: self,action:#selector(HomeTableViewController.leftItemClick))
        navigationItem.rightBarButtonItem = UIBarButtonItem.createBarButtonItem("navigationbar_pop",target: self,action: #selector(HomeTableViewController.rightItemClick))
    }

    func leftItemClick(){
        print(#function)
    }

    func rightItemClick(){
        print(#function)
    }