我有一个简单的类,员工,另一个类,公司,它包含一组员工。公司类有 2 个带有迭代器的嵌套类。一个从第一个到最后一个对项目进行排序,第二个将顺序颠倒过来。正常枚举是默认值。当我尝试在 foreach 循环中使用 ReverseOrder" 时,我收到此错误:
foreach 语句不能对类型的变量进行操作 "Zadanie_1.公司.反向枚举",因为 "Zadanie_1.公司.反向枚举"不包含公共 "获取枚举器"的定义
我的问题是:如何实现自定义迭代器?
public class Employee
{
private string surname, position;
public string Stanowisko { get { return position; } }
public Employee (string nazwisko, string stanowisko)
{
this.surname = nazwisko;
this.position = stanowisko;
}
public override string ToString()
{
return string.Format("nazwisko: {0}, stanowisko: {1}", surname, position);
}
}
public class Company:IEnumerable
{
string name;
private Employee[] employeeArray;
public Company(string nazwa, Employee[] pracownicy)
{
this.name = nazwa;
this.employeeArray = pracownicy;
}
public IEnumerator GetEnumerator()
{
//foreach (Pracownik item in pracownicy)
//{
// yield return item;
//}
return new NormalEnumeration(this);
}
public IEnumerator Ordered()
{
return new NormalEnumeration(this);
}
public override string ToString()
{
return string.Format("Nazwa firmy: {0}, liczba pracowników: {1}", name, employeeArray.Length);
}
public class ReverseEnumeration : IEnumerator
{
Company f;
int counter;
public ReverseEnumeration(Company f)
{
this.f = f;
counter = f.employeeArray.Length;
}
public object Current
{
get
{
Console.WriteLine("Current");
return f.employeeArray[counter];
}
}
public bool MoveNext()
{
if (counter > 0)
{
Console.WriteLine("Move next:");
counter--;
return true;
}
else
return false;
}
public void Reset()
{
counter = f.employeeArray.Length;
}
}
public class NormalEnumeration : IEnumerator
{
Company f;
int counter = -1;
public NormalEnumeration(Company f)
{
this.f = f;
}
public object Current
{
get
{
Console.WriteLine("Current");
return f.employeeArray[counter];
}
}
public bool MoveNext()
{
if (counter >= f.employeeArray.Length-1)
return false;
else
{
counter++;
return true;
}
}
public void Reset()
{
counter = -1;
}
}
}
在问题下评论:
我试图以这种方式调用反向迭代器:
foreach (Employee item in new Company.ReverseEnumeration(instancenamehere)) { Console.WriteLine(item); }
为此,ReverseEnumration
必须实施IEnumerable
.如果希望能够修改枚举器,只需向 Company
类添加新属性。
public class Company : IEnumerable
{
public IEnumerator Enumerator { get; set; }
public IEnumerator GetEnumerator()
{
return Enumerator;
}
// other members
}
可以在构造函数中设置默认枚举器。
public Company(string nazwa, Employee[] pracownicy)
{
Enumerator = new NormalEnumeration(this);
// other stuff
}
您应该从 Company
类中提取枚举器,因为它们无论如何都不使用它的内部结构。这将使您能够轻松地从外部更改枚举器。
var c = new Company(null, null);
c.Enumerator = new ReverseEnumeration(c);