swift 创建类方法(扩展)和便利构造函数

本文主要是介绍swift 创建类方法(扩展)和便利构造函数，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

https://blog.csdn.net/zhengyanfeng1989/article/details/60867795

import UIKit
//UIButton的类方法扩展
extension UIButton {
//这里的类方法相当于OC中的加号方法
class func creatButtonWithImageName(imageName : String , bgImageName : String) -> UIButton {
//创建按钮
let button = UIButton()
//设置按钮的背景图片
button.setBackgroundImage(UIImage(named: bgImageName), for: UIControlState.normal)
button.setBackgroundImage(UIImage(named: bgImageName + "_highlighted"), for: UIControlState.highlighted)
//设置按钮的图片
button.setImage(UIImage(named: imageName), for: UIControlState.normal)
button.setImage(UIImage(named: imageName + "_highlighted"), for: UIControlState.highlighted)
//按照背景图片初始化按钮尺寸
button.sizeToFit()
//返回按钮
return button
}
/*
convenience : 便利，使用convenience修饰的构造函数叫做便利构造函数
便利构造函数通常在对系统的类进行构造函数的扩充时使用
便利构造函数的特点
1.便利构造函数通常是写在extension中
2.便利构造函数init前面需要加载convenience
3.在便利构造函数中需要明确调用self.init
*/
convenience init(imageName : String , bgImageName : String) {
self.init()
//设置按钮的图片
setImage(UIImage(named: imageName), for: UIControlState.normal)
setImage(UIImage(named: imageName + "_highlighted"), for: UIControlState.highlighted)
//设置按钮的背景图片
setBackgroundImage(UIImage(named: bgImageName), for: UIControlState.normal)
setBackgroundImage(UIImage(named: bgImageName + "_highlighted"), for: UIControlState.highlighted)
//按照背景图片初始化按钮尺寸
sizeToFit()
}
}

<code class="language-objc">//
// MainViewController.swift
// ZYFWB
//
// Created by fe on 2017/3/7.
//
import UIKit
class MainViewController: UITabBarController {
//懒加载tabBar选中图片的数组
lazy var selectImages = ["tabbar_home","tabbar_message_center","","tabbar_discover","tabbar_profile"]
//懒加载中间的发布按钮(使用类方法)
//lazy var composeBtn : UIButton = UIButton(imageName : "tabbar_compose_icon_add" , bgImageName : "tabbar_compose_button")
//懒加载中间的发布按钮(使用构造方法)
lazy var composeBtn : UIButton = UIButton.creatButtonWithImageName(imageName : "tabbar_compose_icon_add" , bgImageName : "tabbar_compose_button")
//系统调用函数
override func viewDidLoad() {
super.viewDidLoad()
//设置发布按钮
setupComposeBtn()
}
//系统调用函数
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
//调整tabBar的显示细节问题需要在该方法中，如果在viewDidLoad中调整，则在该方法中会被调整回来
setupTabBarItems()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
// MARK:-设置UI界面
extension MainViewController {
func setupComposeBtn() {
//设置发布按钮位置
composeBtn.center = CGPoint(x: tabBar.center.x, y: tabBar.frame.size.height * 0.5)
//添加发布按钮到tabBar
tabBar.addSubview(composeBtn)
}
//调整tabbaritems
func setupTabBarItems() {
//遍历tabBarItem
for i in 0..<tabBar.items!.count{
//拿到item
let item = tabBar.items![i]
//如果i为2则控制item不能点击
if i == 2 {
item.isEnabled = false
continue
}
//设置item的选中图片
item.selectedImage = UIImage(named: selectImages[i] + "_selected")
}
}
}
</code>