这种流动结构控制是否良好实践？

Question

我想重写一个有太多嵌套if语句的方法.

我提出了这种方法,并希望你的意见:

public void MyMethod()
{
   bool hasFailed = false;

   try
   {
      GetNewOrders(out hasFailed);

      if(!hasFailed)
          CheckInventory(out hasFailed);

      if(!hasFailed)
          PreOrder(out hasFailed);              

      // etc
   }
   catch(Exception ex)
   {
   }
   finally
   {
      if(hasFailed)
      {
           // do something
      }
   }
}

Answer 1

我做过类似的事情,但没有异常处理:

BOOL ok = CallSomeFunction();
if( ok ) ok = CallSomeOtherFunction();
if( ok ) ok = CallYetAnotherFunction();
if( ok ) ok = WowThatsALotOfFunctions();
if( !ok ) {
    // handle failure
}

或者如果你想要聪明:

BOOL ok = CallSomeFunction();
ok &= CallSomeOtherFunction();
ok &= CallYetAnotherFunction();
...

如果您正在使用异常,为什么需要hasFailed变量？

Answer 2

并不是的.如果您的"catch"块捕获到错误,您的方法应引发异常.

Answer 3

据我所知,这是一个级联步骤的例子,如果第一个和第一个和第二个有效,将执行第二个和第三个步骤,即返回hasFailed == false.

使用Template Method和Decorator设计模式可以使代码更加优雅.

您需要一个接口,具体实现,抽象类和抽象类的几个子类.

public interface Validator {
    public boolean isValid();
}

public class GetNewOrders implements Validator {
    public boolean isValid() {
       // same code as your GetNewOrders method
    }
}

public abstract class AbstractValidator implements Validator {
    private final Validator validator;

    public AbstractValidator(Validator validator) {
        this.validator = validator;
    }
    protected boolean predicate();
    protected boolean isInvalid();

    public final boolean isValid() {
        if (!this.validator.isValid() && predicate() && isInvalid())
            return false;
        return true;
    }
}

public class CheckInventory extends AbstractValidator {
    public CheckInventory(Validator validator) {
        super(validator);
    }
    @Override
    public boolean predicate() {
        return true;
    }
    @Override
    public boolean isInvalid() {
        // same code as your CheckInventory method
    }
}

public class PreOrder extends AbstractValidator {
    public CheckInventory(Validator validator) {
        super(validator);
    }
    @Override
    public boolean predicate() {
        return true;
    }
    @Override
    public boolean isInvalid() {
        // same code as your PreOrder method
    }
}

现在你的方法可以看起来更优雅:

public void MyMethod() {
    bool success = false;
    try {
        Validator validator = new GetNewOrders();
        validator = new CheckInventory(validator);
        validator = new PreOrder(validator);
        success = validator.isValid();
    } finally {
        if (!success) {
            // do something
        }
    }
} 

Validator对象可以在一行中创建,但我更喜欢这种样式,因为它明确了验证的顺序.在链中创建新的验证链接是子类化AbstractValidator类以及谓词和isInvalid方法的实现的问题.