c# - C#中的流利接口和继承

Question

我将举例说明一个问题。有一个具有流畅接口的基类：

class FluentPerson
{
    private string _FirstName = String.Empty;
    private string _LastName = String.Empty;

    public FluentPerson WithFirstName(string firstName)
    {
        _FirstName = firstName;
        return this;
    }

    public FluentPerson WithLastName(string lastName)
    {
        _LastName = lastName;
        return this;
    }

    public override string ToString()
    {
        return String.Format("First name: {0} last name: {1}", _FirstName, _LastName);
    }
}

和一个子类：

class FluentCustomer : FluentPerson
{
    private long _Id;

    private string _AccountNumber = String.Empty;

    public FluentCustomer WithAccountNumber(string accountNumber)
    {
        _AccountNumber = accountNumber;
        return this;
    }
    public FluentCustomer WithId(long id)
    {
        _Id = id;
        return this;
    }

    public override string ToString()
    {
        return base.ToString() + String.Format(" account number: {0} id: {1}", _AccountNumber, _Id);
    }
}

问题是当你调用时customer.WithAccountNumber("000").WithFirstName("John").WithLastName("Smith")你不能.WithId(123)最后添加，因为WithLastName()方法的返回类型是 FluentPerson（不是 FluentCustomer）。

这个问题一般是怎么解决的？

score 49 · Accepted Answer

尝试使用一些扩展方法。

static class FluentManager
{
    public static T WithFirstName<T>(this T person, string firstName) where T : FluentPerson
    {
        person.FirstName = firstName;
        return person;
    }

    public static T WithId<T>(this T customer, long id) where T : FluentCustomer
    {
        customer.ID = id;
        return customer;
    }
}

class FluentPerson
{
    public string FirstName { private get; set; }
    public string LastName { private get; set; }

    public override string ToString()
    {
        return string.Format("First name: {0} last name: {1}", FirstName, LastName);
    }
}

class FluentCustomer : FluentPerson
{
    public long ID { private get; set; }
    public long AccountNumber { private get; set; }

    public override string ToString()
    {
        return base.ToString() + string.Format(" account number: {0} id: {1}", AccountNumber, ID);
    }
}

在你可以使用之后

new FluentCustomer().WithId(22).WithFirstName("dfd").WithId(32);

score 45 · Accepted Answer

您可以使用泛型来实现这一点。

public class FluentPerson<T>
    where T : FluentPerson<T>
{
    public T WithFirstName(string firstName)
    {
        // ...
        return (T)this;
    }

    public T WithLastName(string lastName)
    {
        // ...
        return (T)this;
    }
}

public class FluentCustomer : FluentPerson<FluentCustomer>
{
    public FluentCustomer WithAccountNumber(string accountNumber)
    {
        // ...
        return this;
    }
}

现在：

var customer = new FluentCustomer()
  .WithAccountNumber("123")
  .WithFirstName("Abc")
  .WithLastName("Def")
  .ToString();

score 4 · Accepted Answer

从逻辑上讲，您需要配置从最具体（客户）到最不具体（人）的内容，否则即使界面流畅，也很难阅读。在大多数情况下，遵循此规则您不会遇到麻烦。但是，如果出于任何原因您仍然需要混合它，您可以使用中间强调语句，如

static class Customers
{
   public static Customer AsCustomer(this Person person)
   {
       return (Customer)person;
   }
}

customer.WIthLastName("Bob").AsCustomer().WithId(10);

score 4 · Accepted Answer

一个需要流畅接口、继承和一些泛型的解决方案......

无论如何，正如我之前所说：如果你想使用继承和访问受保护的成员，这是唯一的选择......

public class GridEx<TC, T> where TC : GridEx<TC, T>
{
    public TC Build(T type)
    {
        return (TC) this;
    }
}

public class GridExEx : GridEx<GridExEx, int>
{

}

class Program
{
    static void Main(string[] args)
    {
        new GridExEx().Build(1);
    }
}

score 3 · Accepted Answer

 public class FluentPerson
 {
    private string _FirstName = String.Empty;
    private string _LastName = String.Empty;

    public FluentPerson WithFirstName(string firstName)
    {
        _FirstName = firstName;
        return this;
    }

    public FluentPerson WithLastName(string lastName)
    {
        _LastName = lastName;
        return this;
    }

    public override string ToString()
    {
        return String.Format("First name: {0} last name: {1}", _FirstName, _LastName);
    }
}


   public class FluentCustomer 
   {
       private string _AccountNumber = String.Empty;
       private string _id = String.Empty;
       FluentPerson objPers=new FluentPerson();



       public FluentCustomer WithAccountNumber(string accountNumber)
       {
           _AccountNumber = accountNumber;
           return this;
       }

       public FluentCustomer WithId(string id)
       {
           _id = id;
           return this;
       }

       public FluentCustomer WithFirstName(string firstName)
       {
           objPers.WithFirstName(firstName);
           return this;
       }

       public FluentCustomer WithLastName(string lastName)
       {
           objPers.WithLastName(lastName);
           return this;
       }


       public override string ToString()
       {
           return objPers.ToString() + String.Format(" account number: {0}",  _AccountNumber);
       }
   }

并使用调用它

  var ss = new FluentCustomer().WithAccountNumber("111").WithFirstName("ram").WithLastName("v").WithId("444").ToString();

score 3 · Accepted Answer

流畅的接口真的是最好的调用，还是初始化器会更好？

 var p = new Person{
      LastName = "Smith",
      FirstName = "John"
      };

 var c = new Customer{
      LastName = "Smith",
      FirstName = "John",
      AccountNumber = "000",
      ID = "123"
      };

与流利的接口不同，这可以很好地工作，而无需继承方法返回基类并弄乱链。当你继承一个属性时，调用者真的不应该关心FirstName首先是在 Person、Customer 还是 Object 中实现的。

我发现这也更具可读性，无论是单行还是多行，您都不必费心提供与每个属性对应的流畅的自修饰函数。

score 1 · Accepted Answer

我知道这是一个老问题，但我想与您分享我对此的看法。

如果可以的话，如何将流利度（一种机制）和您的课程分开呢？这将使您的课程保持纯净。

这样的事情呢？

课程

    public class Person
    {
        public string FirstName { get; set; }
        public string LastName {get; set;}

        public override string ToString()
        {
            return $"First name: {FirstName} last name: {LastName}";
        }
    }

    public class Customer : Person
    {
        public string AccountNumber { get; set; }
        public long Id { get; set; }

        public override string ToString()
        {
            return base.ToString() + $" account number: {AccountNumber} id: {Id}");
        }
    }

添加一些流畅机制的类

    public class FluentCustomer 
    {
        private Customer Customer { get; }

        public FluentCustomer() : this(new Customer())
        {
        }

        private FluentCustomer(Customer customer)
        {
            Customer = customer;
        }

        public FluentCustomer WithAccountNumber(string accountNumber)
        {
            Customer.AccountNumber = accountNumber;
            return this;
        }

        public FluentCustomer WithId(long id)
        {
            Customer.Id = id;
            return this;
        }

        public FluentCustomer WithFirstName(string firstName)
        {
            Customer.FirstName = firstName;
            return this;
        }

        public FluentCustomer WithLastName(string lastName)
        {
            Customer.LastName = lastName;
            return this;
        }

        public static implicit operator Customer(FluentCustomer fc)
        {
            return fc.Customer;
        }

        public static implicit operator FluentCustomer(Customer customer)
        {
            return new FluentCustomer(customer);
        }
    }

切换到流利模式的扩展方法

    public static class CustomerExtensions 
    {

        public static FluentCustomer Fluent(this Customer customer)
        {
            return customer;
        }
    }

与问题相同的示例


        Customer customer = new Customer().Fluent()
                            .WithAccountNumber("000")
                            .WithFirstName("John")
                            .WithLastName("Smith")
                            .WithId(123);

c# - C#中的流利接口和继承

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