UIAlertController是苹果iOS 8以后推出的弹窗视图，其用来取代UIAlertView，官方也建议在iOS 9之后弃用后者，
前者相比后者来说写法简单易懂，但是代码仍算比较多，所以我使用了block的方式将其简化封装，方便全局和多次使用。也方便以后各种替换这个弹窗。

特意也使用@objc 来提供给OC使用，这样就清爽多啦。

其中也添加了适配iPad的代码。

先来看看使用效果:

// Sheet
let alertController = WSAlertController.alertSheet(title: "Sheet").add(title: "title1", style: .default) {
    // your code
}.add(title: "title2", style: .destructive) {
    // your code        
}.add(title: "title3", style: .cancel) {
   // your code         
}.finish()

// Alert
let alertController = WSAlertController.alertAlert(title: "title", message: "message", okTitle: "ok", cancelTitle: "cancel") {
    // your code 
}

// Input
let alertController = WSAlertController.alertInputViews(title: "title", message: "message", placeholders: ["请输入账号","请输入密码"]) { (inputTextArray) in
    // your code
}

是不是简化了许多。

具体代码：

import UIKit

///可空的无参无返回值 Block
typealias AlertCompleteOptional = (() -> Swift.Void)?
class WSAlertController: NSObject{
    //MARK: 链式初始化方法
    private var title: String?
    private var actionArray: [(String,UIAlertAction.Style,AlertCompleteOptional)] = []
    
    init(title: String?) {
        self.title = title
    }
    
    /// 类方法初始化链式
    @objc class func alertSheet(title: String?) -> WSAlertController{
        return WSAlertController(title: title)
    }
    
    @discardableResult
    @objc func add(title: String, style: UIAlertAction.Style, complete: AlertCompleteOptional) -> WSAlertController{
        actionArray.append((title,style,complete))
        return self
    }
    
    @objc func finish() ->UIAlertController{
        return WSAlertController.alertControllerSheet(title: self.title, actionArray: self.actionArray)
    }
    
    /// 使用actionSheet样式的系统AlertControllerSheet封装
    ///
    /// - Parameters:
    ///   - title: 标题
    ///   - hitSender: 当为ipad设备时给予一个附着的控件
    ///   - actionArray: 每个action独立元组数组
    /// - Returns: 返回这个alertController用于显示出来
    private class func alertControllerSheet(title: String?,
                                            actionArray: [(String,UIAlertAction.Style,AlertCompleteOptional)]) -> UIAlertController{
        
        let alertVC = UIAlertController(title: title, message: nil, preferredStyle: UIAlertControllerStyle.actionSheet)
        for action in actionArray{
            let alertAction = UIAlertAction(title: action.0, style: action.1, handler: { (_) in
                action.2?()
            })
            alertVC.addAction(alertAction)
        }
        addPopPresenterView(alertVC: alertVC)
        return alertVC
    }
    
    
    //MARK: 类方法
    /// 返回alertController 有取消和确定按钮
    ///
    /// - Parameters:
    ///   - title: 标题
    ///   - message: 内容
    ///   - okTitle: 确定按钮的文字
    ///   - okComplete: 回调事件
    /// - Returns: alertController 实例
    @objc class func alertAlert(title: String?, message: String?, okTitle: String, cancelTitle: String? = nil, okComplete: AlertCompleteOptional) -> UIAlertController{
        
        let alertVC = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert)
        let alertAction = UIAlertAction(title: okTitle, style: .default, handler: { (_) in
            if okComplete != nil{
                okComplete!()
            }
        })
        
        let cancel = UIAlertAction(title: cancelTitle ?? "取消", style: .cancel) { (alert: UIAlertAction) -> Void in
        }
        
        alertVC.addAction(alertAction)
        alertVC.addAction(cancel)
        addPopPresenterView(alertVC: alertVC)
        return alertVC
    }
    
    /// 返回alertController 仅确定按钮
    ///
    /// - Parameters:
    ///   - title: 标题
    ///   - message: 内容
    ///   - okTitle: 确定按钮的文字
    ///   - okComplete: 回调事件
    /// - Returns: alertController 实例
    @objc class func alertAlert(title: String?, message: String?, okTitle: String, okComplete: AlertCompleteOptional) -> UIAlertController{
        
        let alertVC = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert)
        let alertAction = UIAlertAction(title: okTitle, style: .default, handler: { (_) in
            if okComplete != nil{
                okComplete!()
            }
        })
        alertVC.addAction(alertAction)
        addPopPresenterView(alertVC: alertVC)
        return alertVC
    }
    
    
    /// 多个输入框的alertController
    ///
    /// - Parameters:
    ///   - title: 标题
    ///   - message: 内容
    ///   - placeholders: 多少个提示文字 代表多少个框
    ///   - okComplete: 回调字符串数组 数组内容顺序是输入框的顺序
    public class func alertInputViews(title: String?,
                                      message: String?,
                                      placeholders: [String]?,
                                      okComplete: @escaping ((_ text: [String]) -> Void)) -> UIAlertController{
        let alertVC = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert)
        
        if let placeholderList = placeholders{
            for placeholder in placeholderList{
                alertVC.addTextField { (textField) in
                    textField.placeholder = placeholder
                }
            }
        }
        
        let okAction = UIAlertAction(title: "确定", style: UIAlertActionStyle.default) { (action) in
            if let textFields = alertVC.textFields{
                var inputText: [String] = []
                for textfield in textFields{
                    if let text = textfield.text{
                        inputText.append(text)
                    }
                }
                okComplete(inputText)
            }
        }
        let cancelAction = UIAlertAction(title: "取消", style: UIAlertActionStyle.cancel) { (action) in
        }
        alertVC.addAction(okAction)
        alertVC.addAction(cancelAction)
        addPopPresenterView(alertVC: alertVC)
        return alertVC
    }
    
    /// 适配iPad
    private class func addPopPresenterView(alertVC: UIAlertController){
        if UIDevice.current.userInterfaceIdiom == UIUserInterfaceIdiom.pad {
            let popPresenter = alertVC.popoverPresentationController
            if let keywindow = UIApplication.shared.keyWindow{
                popPresenter?.sourceView = keywindow
                if alertVC.preferredStyle == UIAlertControllerStyle.alert {
                    popPresenter?.sourceRect = CGRect(x: keywindow.width()/2, y:keywindow.height()/2, width: 0, height: 0)
                }else {
                    popPresenter?.sourceRect = CGRect(x: keywindow.width()/2, y: keywindow.height(), width: 0, height: 0)
                }
                popPresenter?.permittedArrowDirections = []
            }
        }
    }

}