Swift3.0项目学习: 创建撰写按钮

import UIKit

class PSMainViewController: UITabBarController {

    override func viewDidLoad() {
        super.viewDidLoad()
        setupChildControllers()
        addComposeButton()
    }
    // MARK: - 私有控件 懒加载<iOS10好像写private就访问不到,报错!>
     lazy var composeButton: UIButton = UIButton.cz_imageButton("tabbar_compose_icon_add_highlighted", backgroundImageName: "tabbar_compose_button")
}

//MARK: 设置子控制器
extension PSMainViewController{
    
    // 添加撰写按钮
     func addComposeButton(){
        tabBar.addSubview(composeButton)
        // 设置按钮的位置
        let count = CGFloat(childViewControllers.count)
        let width = tabBar.bounds.width / count - 1   // 减一注意是设置容错点
        // insetBy设置偏移 正数向内缩进,附属向外扩展
        composeButton.frame = tabBar.bounds.insetBy(dx: 2 * width, dy: 0)
    }