第20章：错误处理（119）

源代码：

//程序目的：学习《从零开始学swift》
//第20章：错误处理
//Create By ChenZhen

enum DAOError: Error {
    case Nodata
    case PrimaryKeyNull
}

class Note {
    var date: NSDate?
    var content: String?
    
    init(date: NSDate?, content: String?) {
        self.date = date
        self.content = content
    }
}

class NoteDAO {
    //保存数据列表
    private var listData = [Note]()
    
    //插入Note方法
    func create(model: Note) {
        listData.append(model)
    }
    
    //删除Note方法
    func remove(model: Note) throws {
        guard let date = model.date else {
            //抛出“主键为空”错误
            throw DAOError.PrimaryKeyNull
        }
        //比较日期主键是否相等
        for (index, note) in listData.enumerated() where note.date == date {
            listData.remove(at: index)
        }
    }
    
    //修改Note方法
    func modify(model: Note) throws {
        guard let date = model.date else {
            //抛出主键为空的错误
            throw DAOError.PrimaryKeyNull
        }
        //比较日期主键是否相等
        for note in listData where note.date == date {
            note.content = model.content
        }
    }
    
    //查询所有数据的方法
    func findAll() throws -> [Note] {
        guard listData.count  > 0 else {
            //抛出“没有数据”错误
            throw DAOError.Nodata
        }
        defer {
            print("关闭数据库")
        }
        defer {
            print("释放语句对象")
        }
        return listData
    }
    
    //修改Note方法
    func findBy(model: Note) throws -> Note? {
        guard let date = model.date else {
            //抛出主键为空的错误
            throw DAOError.PrimaryKeyNull
        }
        //比较日期主键是否相等
        for note in listData where note.date == date {
            return note
        }
        return nil
    }
}


//测试示例
//日期格式对象
var dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"

let dao = NoteDAO()

//查询所有数据
do {
    try dao.findAll()
} catch DAOError.Nodata {
    print("没有数据")
    
    //准备要插入的数据
    var date1: NSDate = dateFormatter.date(from: "2016-01-01 16:01:03")! as NSDate
    var note1: Note = Note(date: date1, content: "welcome to mynote.")
    var date2: NSDate = dateFormatter.date(from: "2016-01-02 8:01:03")! as NSDate
    var note2: Note = Note(date: date2, content: "欢迎使用mynote。")
    //插入数据
    dao.create(model: note1)
    dao.create(model: note2)
}

do {
    var note: Note = Note(date: nil, content: "welcome to mynote")
    try dao.remove(model: note)
} catch DAOError.PrimaryKeyNull {
    print("主键为空。")
}

func printNotes() throws {
    let datas = try dao.findAll()
    for note in datas {
        print("date: \(note.date!) - content: \(note.content!)")
    }
}

try printNotes()