Question

目前,Im试图实施Transaction 字典模式(实际上,Martin Fowler 。通过在简单的测试项目中使用 Command Format,一切只是工作罚款,问题在于我不知道如何在从ICommand界面继承的具体类别中执行特定方法时取得结果。

Let s show you some code to clarify what functionality I have. I ve a simple CalculateSalaryCommand class which inherited from ICommand interface

public class CalculateSalaryCommand : ICommand
{
    private readonly CalculateSalaryTS _salaryTs;
    private readonly int _hour;
    private readonly int _salaryPerHour;

    public CalculateSalaryCommand(CalculateSalaryTS salaryTs, int hour, int salaryPerHour)
    {
        _salaryTs = salaryTs;
        _hour = hour;
        _salaryPerHour = salaryPerHour;
    }

    public void Execute()
    {
        _salaryTs.CalculateSalary(_hour, _salaryPerHour);
    }
}

and a simple Transaction Script class named CalculateSalaryTS

public class CalculateSalaryTS {
    public void CalculateSalary(int _hour, int _salaryPerHour) {
        Result = _hour * _salaryPerHour;
    }
}

as you can see I pass the instance of to concrete command class, then inside the Execute method I execute a operations from that instance. Well, everything just look good. but there is a problem I can t return the result of executed method which is should be a integer. To handle this problem, I decided to add some code to Transaction Script layer which each transaction should inherit from a generic ITransactionResult interface, which is look like following:

public interface ITransactionResult<TResult>
{
    TResult Result { get; set; }
}

然后,计算仪表相仿:

public class CalculateSalaryTS : ITransactionResult<Int32> {

    public void CalculateSalary(int _hour, int _salaryPerHour) {
        Result = _hour * _salaryPerHour;
    }

    public int Result { get; set; }

}

<<>Usage>:

    var script = new CalculateSalaryTS();
    var command = new CalculateSalaryCommand(script, 10, 20);           
    command.Execute();
    Console.WriteLine("Salary is {0}", script.Result);

我知道这种方式有其局限性,但我别无选择,直到你给我另一种处理这种情况的想法。

提前感谢。

Answer 1

如果你绝对需要在指挥执行后立即取得结果,你可以储存导致指挥目标的结果:

public interface ICommandWithResult<T> : ICommand
{
  T Result { get; }
}

public class CalculateSalaryCommand : ICommandWithResult<int>
{
  public int Result { get; private set; }

  // ...

  public void Execute()
  {
    _salaryTs.CalculateSalary(_hour, _salaryPerHour);
    this.Result = _salaryTs.Result;
  }
}

// Usage:

var command = new CalculateSalaryCommand(new CalculateSalaryTS(), 10, 20);
command.Execute();
Console.WriteLine("Salary is {0}", command.Result);

Answer 2

我认为,你正在寻找能够恢复结果的指挥模式。

因此,

    interface ICommand<TResult>
    {
       TResult Execute();
    }


public class CalculateSalaryCommand : ICommand<int>
{
    private readonly CalculateSalaryTS _salaryTs;
    private readonly int _hour;
    private readonly int _salaryPerHour;

    public CalculateSalaryCommand(CalculateSalaryTS salaryTs, int hour, int salaryPerHour)
    {
        _salaryTs = salaryTs;
        _hour = hour;
        _salaryPerHour = salaryPerHour;
    }

    public int Execute()
    {
        return _salaryTs.CalculateSalary(_hour, _salaryPerHour);
    }
}

友情链接