Swift一些概念定义 | 三

一，创建闭包属性，赋值并且执行，使其弱引用：

    var flag: Bool = false;
    //定义
    var operate: ((String) -> String)? ;
    //
    override func viewDidLoad() {
        super.viewDidLoad()
        //赋值
        self.operate = {
            [weak self]
            (text: String) -> String in
            return "\(text) + \(self!.flag)";
        };
        //执行
        let op = operate!("this is block");
        print(op);
    }

一般应用于：
var operate_q: (() -> Void)?;
self.dismiss(animated: true, completion: self.operate_q);

二，反向传递bolck，外部处理内部事物，通过代理传递出block：

typealias RecordListPlayButtonSelectedHandle = (_ isChange: inout Bool) -> Void;

protocol SKRecordListCellProtocol: NSObjectProtocol {
    ///点击播放或暂停
    func recordListCellPlayAndPauseOperate(recordListCell:SKRecordListCell,playAndPauseButton: UIButton,selectedHandle: RecordListPlayButtonSelectedHandle) -> Void;
}
///
    ///播放，暂停
    @objc func playAndPauseEvent(_ sender: UIButton) -> Void {
        if delegate != nil {
            let selectedHandle: RecordListPlayButtonSelectedHandle = {
                (isChange: inout Bool) -> Void in
                print(isChange);
                if isChange == true {
                    sender.isSelected = !sender.isSelected;
                }
            };
            delegate?.recordListCellPlayAndPauseOperate(recordListCell: self, playAndPauseButton: sender, selectedHandle: selectedHandle);
        }
    }

///实现
extension SKHomePageController: SKRecordListCellProtocol {
  
    ///播放，暂停代理
    func recordListCellPlayAndPauseOperate(recordListCell: SKRecordListCell, playAndPauseButton: UIButton, selectedHandle: (inout Bool) -> Void) {
        print("recordListCellPlayAndPauseOperate");
        var isChange = true;
        selectedHandle(&isChange);
    }
}

三，swift数组转换成c语言数组指针：

var bytes: [Float32] = [39.0, 77.0, 111.0, 111.0, 102.0, 33.0, 39.0, 0.0];
let float32Pointer = UnsafeMutablePointer<Float32>.allocate(capacity: 8);
float32Pointer.initialize(from: &bytes, count: 8);
print("float32Pointer - - - \(float32Pointer)");

四，定义OC和swift不同的类名：

// OC用MLKText，swift用Text
//
NS_SWIFT_NAME(Text)
@interface MLKText : NSObject
//
//

五，Swift遍历数组。

//
//
let resultModels: [SkyPredictorResultModel] = predictions.map { prediction in
//prediction为其中的某一个元素
}
//
//

Swift遍历数组，获取数组中的前两个：

//
//
let resultModels: [SkyPredictorResultModel] = predictions.prefix(2).map { prediction in
//prediction为其中的某一个元素
}
//
//