如何定义“ isValid”？有理有据 [英] how to define "isValid" function with reason

问题描述

我正在尝试在文件生成程序中的某些状态下建模
：

I am trying to model some states in my file generation program, at one point :

1. 我要检查数据的当前状态


2. 如果数据有效，我要继续


3. 否则，我想通知用户无法继续的原因

伪代码如下：

if(isValid()){
    writeFile()
} else {
    switch(getReason()){
        case FAIL1: doSomething1();
            break;
        case FAIL2: doSomething2();
            break;
        case FAIL3: doSomething3();
            break;
    }
}

不确定这种方法是否正确，像您的建议/意见。其中：总共有少于10个错误状态，并且在给定时间仅适用一个错误状态。

Not sure if an approach like this is correct, would like your advice/opinions. Where: in total there are less than 10 error states, and only one error state is applicable at a given time.

推荐答案

来自加尔纳弗的想法正在朝着良好的方向发展；但是从面向对象的角度来看，它仍然不是一个很好的解决方案。

The idea from garnulf is going in a good direction; but it is still not a really good solution in OO terms.

事情是：您已经提到了重要的关键概念：状态，就像在状态机中一样。

Thing is: you already mentioned the key concept that is important here: state, as in state machine.

您真的想在这里使用多态性：

You really want to use polymorphism here:

abstract class Reason() {
   String getMessage() { // just to show that there might be some shared code
   abstract void doSomething();

然后，您的Reason类将具有不同的子类；最后，您的客户代码归结为：

Then you would have different subclasses for your Reason class; and in the end, your client code boils down to:

getReason().doSomething();

因为每个原因都知道该怎么做！当然，这可能需要进一步思考-取决于这些不同错误原因的真正原因。

Because each reason knows whats to do about itself! Of course, that might require some further thinking - depending on the fact what those different error reasons are really about.

关键点是：您真的想避免任何对枚举或字符串值的切换。如果有的话，您将这样的开关隐藏在工厂内部，这会返回一些抽象类/接口（工厂将在其中为您创建一个具体的子类/实现）。

The key point is: you really want to avoid any kind of switching over enum or string values. If at all, you hide such switches inside of factories, that return some abstract class / interface thingy (where the factory creates a concrete subclass/implementation for you).

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