如何扩展类

本文关键字：扩展 何扩展 | 更新日期: 2023-09-27 17:53:44

我正在对提供数据的API进行更改。有些搜索需要作者的数据，并采用IAuthor对象。该API有一个IAuthor接口和一个实现IAuthor的具体类Author。

我需要添加一个布尔属性，IsNovelist，这将改变一些但不是所有搜索的语义。

我听说过开放/封闭原则，似乎改变IAuthor和/或Author类会违反这个原则。那么如何做出这个简单的改变呢?

更新:

也许我把注意力集中在错误的课程上。我不想添加行为到Author类(它只是传递参数给API的一种方式)。因此，Decorated作者不需要布尔标志，因为它将隐含为isNovelist == true。

我需要改变GetBooks方法的行为给定的作者谁被标记为小说家。所以更像这样的东西，但我的想法可能是不稳定的，因为现在我正在改变(不扩展)Books类:

//Before
class Books 
{
   public Books[] GetBooks(IAuthor author){
       // Call data access GetBooks...
    }
}

//After
class Books 
{
   public Books[] GetBooks(IAuthor author){
       // To maintain pre-existing behaviour
       // call data access GetBooks with SQL param @isNovelist = false...
       // (or don't pass anything because the SQL param defaults to false)
    }
   public Books[] GetBooksForNovelist(IAuthor author){
       // To get new behaviour
       // call data access GetBooks with SQL param @isNovelist = true
    }
}

如何扩展类

方案二:

class Program
{
    private static void Main(string[] args)
    {
        IAuthor author = new Novelist();
        author.Name = "Raj";
        // i guess u have check if author is a novelist
        // the simple way is by safe typecasting
        Novelist novelist = author as Novelist;
        if (novelist != null)
        {
            Console.WriteLine("Wohoo, i am a novelist");
        }
        else
        {
            Console.WriteLine("Damn,i cant write novel");
        }

    }

方案1:

public enum AuthourType
{
    Novelist,
    Other
}
public interface IAuthor
{
    string Name { get; set; }
    AuthourType Type { get; set; }
}
public class  Novelist : IAuthor
{
    public string Name { get; set; }
    public AuthourType Type { get; set; }
    // incase u dont want it to be set to other value
    /*        
    public AuthourType Type
    {
        get { return type; }
        set
        {
            if (value != AuthourType.Novelist)
            {
                throw new NotSupportedException("Type");
            }
            type = value;
        }
    }
    */
}

如何使用装饰器模式

interface IAuthor
{
    void someMethod();
}
class Author:IAuthor{
    public void someMethod(){
        //Implementation here
    }
}
//Class that will add the extra behavior.
class DecoratedAuthor : IAuthor
{
    IAuthor author;
    public bool isNovelist{get;set;}//Add the extra Behavior
    public DecoratedAuthor(IAuthor auth)
    {
        this.author = auth;
    }
    public void someMethod(){
        //Call the Author's version here
        author.someMethod();
        //check if he is a novelist
        isNovelist = true;
    }
}

public class program{
    public static void Main(string[] args)
    {
        IAuthor auth = new Author();
        DecoratedAuthor novAuth = new DecoratedAuthor(auth);
        DecoratedAuthor.someMethod();
        //see if he is a novelist
        Console.WriteLine(novAuth.isNovelist);
    }
}
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