iOS开发笔记之代码设计思路_视图模型

简介: 利用范型对同一类的数据模型统一转换为同一种视图模型

定义协议

//让数据模型遵守这个协议
protocol ZYFText {
    var title: String?{get}
}

定义视图模型

class ZYFTextViewModel: NSObject {

    var title: String?

    private var font: UIFont

    private var minWidth: CGFloat

    private var edgeInsets: UIEdgeInsets

    private var stringWidth: CGFloat {
        guard let text = title else {
            return minWidth
        }
        return text.sizeWithFont(font).width
    }

    var viewWidth: CGFloat {
        let width = self.stringWidth + self.edgeInsets.left + self.edgeInsets.right
        return max(width, minWidth)
    }
    //利用范性，通过遵守ZYFText协议的数据模型，获取视图尺寸方面的数据
    init<T: ZYFText>(item: T, font: UIFont, minWidth: CGFloat, edgeInsets: UIEdgeInsets) {
        super.init()
        self.title = item.title
        self.font = font
        self.minWidth = minWidth
        self.edgeInsets = edgeInsets
        }
    }

viewController中的应用

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        let minWidth: CGFloat = 60
        let font = UIFont.systemFont(ofSize: 15)
        let edgeInsets = UIEdgeInsets(top: 0, left: 20, bottom: 0, right: 20)
        let item = datasource[indexPath.row]
        let textModel = ZYFTextViewModel(item: item, font: font, minWidth: minWidth, edgeInsets: edgeInsets)
        return CGSize(width: textModel.viewWidth, height: 40)
    }