如何避免多重嵌套的IF [英] How to avoid multiple nested IFs

问题描述

我目前正在调整自己的计划，以更加面向对象和更好地实施已知模式等。

I am currently trying to restructure my program to be more OO and to better implement known patterns etc.

我有相当多的嵌套的IF语句，并希望得到摆脱他们。我怎么能去呢？我的第一个方法是把它与例外完成的，所以如

I have quite many nested IF-statements and want to get rid of them. How can I go about this? My first approach was to get it done with exceptions, so e.g.

public static Boolean MyMethod(String param) {
 if (param == null)
  throw new NullReferenceException("param may not be null");

 if (param.Equals("none") || param.Equals("0") || param.Equals("zero"))
  throw new ArgumentNullException("param may not be zero");

 // Do some stuff with param
 // This is not executed if param is null, as the program stops a soon
 // as one of the above exceptions is thrown
}

该方法是在主类的应用程序中使用，如：

The method is used in the main class of the application, e.g.

static void Main() {
 try {
  Boolean test = MyClass.MyMethod(null); // Will throw an exception
 } catch (Exception ex) {
  MessageBox.Show(ex.Message, "Error");
 }

我认为这是相当不错的，因为它可以防止那些语句，几乎所有行动是很好的安排在一个水平的方法。

I think this is quite nice, as it prevents the nested statements and nearly all of the methods actions are nicely arranged on one level.

与IF语句，该方法是这样的。

As with IF-statements, the method would look like this

public Boolean MyMethod(String param) {
 if (param != null) {
  if (!param.Equals("none") && !param.Equals("0") && !param.Equals("zero")) {
   // Do some stuff with param
  } else {
   MessageBox.Show("param may not be zero", "Error");
 } else {
  MessageBox.Show("param may not be null", "Error");
 }
}

我觉得这非常，非常难看，难以维持

Which I find very, very ugly and hard to maintain.

现在的问题是;这是做法的好的？我知道，这可能是主观的，但你如何克服国际单项体育联合会的嵌套（1级或2级也不差，但之后变得更糟......）

Now, the question is; is this approach good? I know, that might be subjective, but how do you overcome nested IFs (1 or 2 levels are not that bad, but it gets worse after that...)

推荐答案

这真的取决于他们的目的。在第一个样品中，if语句执行服务合同，确保输入的方法满足一定的要求的目的。在这种情况下，我自己的代码往往看起来非常像你的代码。

It really depends on their purpose. In your first sample, the if statements serves the purpose of enforcing a contract, making sure that the input to the method meets certain requirements. In those cases, my own code tend to look pretty much like your code.

在使用if块控制方法的流（而不是强制执行的情况下，合同），它有时会有点困难。有时候我会遇到如下代码（极度简化的）例子：

In the case of using the if blocks to control the flow of a method (rather than enforcing a contract), it can sometimes be a bit harder. Sometimes I come across code like the following (extremely simplified) example:

private void SomeMethod()
{
    if (someCondition == true)
    {
        DoSomething();
        if (somethingElse == true)
        {
           DoSomethingMore();
        }
    }
    else
    {
        DoSomethingElse();
    }
}

在这种情况下，它好像该方法具有身兼数职，所以在​​这种情况下，我可能会选择将其分割成几个方法：

In this case, it seems as if the method has several responsibilities, so in this case I would probably choose to split it into several methods:

private void SomeMethod()
{
    if (someCondition == true)
    {
        DoItThisWay();
    }
    else
    {
        DoSomethingElse();
    }
}

private void DoItThisWay()
{
    DoSomething();
    if (somethingElse == true)
    {
       DoSomethingMore();
    }
}

这使得每个方法多用更少的嵌套代码更简单，并且还可以提高可读性，如果方法是给定好名称

This makes each method much simpler with less nested code, and may also increase the readability, if the methods are given good names.

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