Swift Block 回调示例

控制器 A 和 B, 从A push 进来了 B, B 活干完了把作业交给 A

B:

import UIKit

class BlockViewController: UIViewController {

    /// 声明一个 Block
    var myBlock: ((String) -> ())?

    override func viewDidLoad() {
        super.viewDidLoad()

        //任意位置调用
        myBlock?("即将结束")
    }
}

A:

 override func viewDidLoad() {
        super.viewDidLoad()
    
        let vc = BlockViewController()
        //在任意位置接收?
        vc.myBlock = { message in
            print("接收: \(message)")
        }
    navigationController?.pushViewController(vc, animated: true);
}