Below code is from the article in CodeProject website. It is an example that explains **Code of responsibility design pattern**. Here is the link "https://www.codeproject.com/articles/494241/understanding-and-implementing-chain-of-responsibi"
我无法理解何时 tl.ApplyLeave（new Leave（Guid.NewGuid（），15））; 行在主方法中执行并且LeaveApplied Supervisor属性上的方法称为 Supervisor.LeaveApplied（this，l）; 其中 this 指向 void TeamLeader_onLeaveApplied（Employee e，）中的ProjectLeader类类型的对象离开l）方法然后如何调用基类中的方法Employee public void LeaveApplied（Employee s，Leave leave）第一个参数 Employee s 一直指向对象键入TeamLeader。这怎么可能？不应该员工指向 ProjectLeader 类型的对象。请帮我理解这是怎么发生的？谢谢你的帮助。
public abstract class Employee
{
// Every employee will have a supervisor
protected Employee supervisor;
// Event mechanism to know whenever a leave has been applied
public delegate void OnLeaveApplied(Employee e, Leave l);
public event OnLeaveApplied onLeaveApplied = null;
// This will invoke events when the leave will be applied
// i.e. the actual item will be handed over to the hierarchy of
// concrete handlers.
public void LeaveApplied(Employee s, Leave leave)
{
if (onLeaveApplied != null)
{
onLeaveApplied(this, leave);
}
}
// This is the function which concrete handlers will use to take
// action, if they are able to take actions.
public abstract void ApproveLeave(Leave leave);
// getter to get the supervisor of current employee
public Employee Supervisor
{
get
{
return supervisor;
}
set
{
supervisor = value;
}
}
// Using this we can apply for leave
public void ApplyLeave(Leave l)
{
LeaveApplied(this, l);
}
}
public class TeamLeader : Employee
{
// team leas can only approve up to 7 days of leave
const int MAX_LEAVES_CAN_APPROVE = 10;
// in constructor we will attach the event handler that
// will check if this employee can process or he needs to
// pass on to next employee
public TeamLeader()
{
this.onLeaveApplied += new OnLeaveApplied(TeamLeader_onLeaveApplied);
}
// in this function we will check if this employee can
// process or he needs to pass on to next employee
void TeamLeader_onLeaveApplied(Employee e, Leave l)
{
// check if we can process this request
if (l.NumberOfDays < MAX_LEAVES_CAN_APPROVE)
{
// process it on our level only
ApproveLeave(l);
}
else
{
// if we cant process pass on to the supervisor
// so that he can process
if (Supervisor != null)
{
Supervisor.LeaveApplied(this, l);
}
}
}
// If we can process lets show the output
public override void ApproveLeave(Leave leave)
{
Console.WriteLine("LeaveID: {0} Days: {1} Approver: {2}",
leave.LeaveID, leave.NumberOfDays, "Team Leader");
}
}
class ProjectLeader : Employee
{
const int MAX_LEAVES_CAN_APPROVE = 20;
// in constructor we will attach the event handler that
// will check if this employee can process or he needs to
// pass on to next employee
public ProjectLeader()
{
this.onLeaveApplied += new OnLeaveApplied(ProjectLeader_onLeaveApplied);
}
// in this function we will check if this employee can
// process or he needs to pass on to next employee
void ProjectLeader_onLeaveApplied(Employee e, Leave l)
{
// check if we can process this request
if (l.NumberOfDays < MAX_LEAVES_CAN_APPROVE)
{
// process it on our level only
ApproveLeave(l);
}
else
{
// if we cant process pass on to the supervisor
// so that he can process
if (Supervisor != null)
{
Supervisor.LeaveApplied(this, l);
}
}
}
// If we can process lets show the output
public override void ApproveLeave(Leave leave)
{
Console.WriteLine("LeaveID: {0} Days: {1} Approver: {2}",
leave.LeaveID, leave.NumberOfDays, "Project Leader");
}
}
class Program
{
static void Main(string[] args)
{
// lets create employees
TeamLeader tl = new TeamLeader();
ProjectLeader pl = new ProjectLeader();
HR hr = new HR();
// Now lets set the hierarchy of employees
tl.Supervisor = pl;
pl.Supervisor = hr;
// Now lets apply 5 day leave my TL
tl.ApplyLeave(new Leave(Guid.NewGuid(), 5));
// Now lets apply 15 day leave my TL
tl.ApplyLeave(new Leave(Guid.NewGuid(), 15));
// Now lets apply 25 day leave my TL
tl.ApplyLeave(new Leave(Guid.NewGuid(), 25));
// Now lets apply 35 day leave my TL
tl.ApplyLeave(new Leave(Guid.NewGuid(), 35));
Console.ReadLine();
}
答案 0 :(得分：0)
tl.ApplyLeave(new Leave(Guid.NewGuid(), 15));不确定你在这里不明白，它会在tl.ApplyLeave(new Leave(Guid.NewGuid(), 5));之后执行
主管在Main()：
tl.Supervisor = pl;
pl.Supervisor = hr;
因此，只要满足此条件，就会调用此Supervisor.LeaveApplied(this, l);：
// check if we can process this request
if (l.NumberOfDays < MAX_LEAVES_CAN_APPROVE)
{
// process it on our level only
ApproveLeave(l);
}
else
{
// if we cant process pass on to the supervisor
// so that he can process
if (Supervisor != null)
{
Supervisor.LeaveApplied(this, l);
}
}
public void LeaveApplied(Employee s, Leave leave)，是Employee s首先是TeamLeader的对象，但是，查看上面的条件语句，Supervisor.LeaveApplied(this, l);主管调用该方法，因为请假大于10天，因此它是ProjectLeader
此外，如果您通过自己单步调试代码并查看每个方法的调用方式，您可以更好地理解它。
修改
再次查看之后，确实不需要public void LeaveApplied(Employee s, Leave leave)它应该只是public void LeaveApplied(Leave leave)因为在该方法的内部是：
if (onLeaveApplied != null)
{
onLeaveApplied(this, leave);
}
所以我没有看到Employee s的重点。