2. 处理脚本命令行参数

一旦你的脚本开始变得更加高级，你就会想利用这个参数来让你的脚本执行多种操作。例如，如果你在写一个气闸脚本，你会想告诉脚本让一个气闸循环进出，甚至让哪个气闸循环。我不会告诉你如何写一个气闸脚本，但我将以此为例，向你展示如何检测和处理与这种脚本有关的参数。可编程块API有一个内置的命令行解析器，这是由你提供的，它被设计成快速和分配友好，以及易于使用。

对于那些只想继续使用它的人，这里是本教程中使用的简单演示脚本的链接。气闸门

1. MyCommandLine

这段代码初始化了命令行解析器，并试图解析传入的参数。如果它找到了参数，TryParse方法将返回true

MyCommandLine _commandLine = new MyCommandLine();

public void Main(string argument)
{
    if (_commandLine.TryParse(argument)) {
        // The command line parser found arguments in the string.
    }
}
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2. The Argument Formats

传统的命令行中包含了argument和switch

cycle "Airlock 1" in -emergency
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(1) argument

argument: 是以空格为间隔的字符串(cycle)或("Airlock 1")字符串。当argument串有空格分开的过个单词组成，需要用引号概括。
argument的访问和数组一样，通过位置访问元素。第一个元素下标是0，依此类推。
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(2) switch

格式： -emergency
访问：switches放置在任何地方都行，不通过位置访问。

(3) 例子

eg1和eg2显示，放置 -emergency 开关的位置无关紧要，它不会影响参数的索引。

cycle "Airlock 1" in -emergency  #eg1
-emergency cycle "Airlock 1" in   # eg2
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• eg1:
  arguments:

0: cycle
1: "Airclock 1"
2: in
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switch:

-emergency
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• eg2:
  arguments:

0: cycle
1: "Airclock 1"
2: in
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switch:

-emergency
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3、arguments和switches的解析

MyCommandLine类提供方法：Switch(name)，获取名字为name的switch的参数。

(1) MyCommandLine::Switch(strname)

// check if the -myflag switch is set
bool switchIsSet = _commandLine.Switch("myflag");
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(2) MyCommandLine::Arguments(idx)

// retrieve the first argument of the string (either a word or a "quoted string"). The quotes are removed for you.
string arg = _commandLine.Argument(0);
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(3) 命令和参数绑定

首先，我们将需要一种方法来区分命令。第一个参数，当然，将是命令指示器。我们将创建一个字典来保存这些命令。

Dictionary _commands = new Dictionary(StringComparer.OrdinalIgnoreCase);
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注意，我们传入了一个不区分大小写的字符串比较器，所以我们可以接受CYCLE以及cycle。接下来我们需要初始化这些命令。这一点我们在脚本构造函数中完成。

• _commands字典，绑定arguments和action

//_commands字典，绑定arguments和action
public Program() 
{
    // Associate the Cycle method with the cycle command
    _commands["cycle"] = Cycle;
}

public void Cycle()
{
	// This method will hold the code to perform the desired action
}
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• 编辑Main方法来使用这个字典来选择和执行命令。

public void Main(string argument)
{
	// 解析命令行参数
    if (_commandLine.TryParse(argument))
    {
        Action commandAction;

        // Retrieve the first argument. Switches are ignored.
        string command = _commandLine.Argument(0);

        // Now we must validate that the first argument is actually specified, 
        // then attempt to find the matching command delegate.
        if (command == null)
        {
            Echo("No command specified");
        } 
        else if (_commands.TryGetValue(command, out commandAction))
        {
            ///< 在Programs()中绑定了"cycle"字符串和函数Cycle()
            ///< 从字典_commands中取出"cycle"对应的Action执行
            commandAction();
        }
        else
        {
            Echo($"Unknown command {command}");
        }
    }
}
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• 最后，我们必须在与cycle命令相关的Cycle方法中完成对命令特定参数的处理。

public void Cycle()
{
    //解析switch参数emergency
    bool emergencyCycle = _commandLine.Switch("emergency");

    //命令行中解析气闸门的名字，用于cycle。这里index=1。没有气闸门就退出
    string airlockName = _commandLine.Argument(1);
    if (airlockName == null)
    {
        Echo("Cannot cycle, no airlock specified");
        return;
    }

    // Argument no. 2 should be either "in" or "out", indicating
    // which direction to cycle
    ///< 命令行中读取index=2的参数，确定进出方向in/out
    string direction = _commandLine.Argument(2);
    if (direction == null)
    {
        Echo($"Cannot cycle {airlockName}, no direction specified");
        return;
    }
    if (string.Equals(direction, "in", StringComparison.OrdinalIgnoreCase))
    {
        Echo($"Cycling airlock {airlockName} in...");
        // TODO: Begin the cycling of the airlock
    }
    else if (string.Equals(direction, "out", StringComparison.OrdinalIgnoreCase))
    {
        Echo($"Cycling airlock {airlockName} out...");
        // TODO: Begin the cycling of the airlock
    }
    else
    {
        // The argument was none of the expected values
        Echo($"Cannot cycle {airlockName}, cannot understand direction {direction}");
    }
}
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4. code example

MyCommandLine _commandLine = new MyCommandLine();
Dictionary _commands = new Dictionary(StringComparer.OrdinalIgnoreCase);

public Program()
{
    _commands["cycle"] = Cycle;
}

public void Cycle()
{
    // Check if the "emergency" switch is set.
    bool emergencyCycle = _commandLine.Switch("emergency");

    // Argument no. 1 is the name of the airlock to cycle
    string airlockName = _commandLine.Argument(1);
    if (airlockName == null)
    {
        Echo("Cannot cycle, no airlock specified");
        return;
    }

    // Argument no. 2 should be either "in" or "out", indicating
    // which direction to cycle
    string direction = _commandLine.Argument(2);
    if (direction == null)
    {
        Echo($"Cannot cycle {airlockName}, no direction specified");
        return;
    }

    if (string.Equals(direction, "in", StringComparison.OrdinalIgnoreCase))
    {
        Echo($"Cycling airlock {airlockName} in...");
        // TODO: Begin the cycling of the airlock
    }
    else if (string.Equals(direction, "out", StringComparison.OrdinalIgnoreCase))
    {
        Echo($"Cycling airlock {airlockName} out...");
        // TODO: Begin the cycling of the airlock
    }
    else
    {
        // The argument was none of the expected values
        Echo($"Cannot cycle {airlockName}, cannot understand direction {direction}");
    }
}

public void Main(string argument)
{
    if (_commandLine.TryParse(argument))
    {
        Action commandAction;

        // Retrieve the first argument. Switches are ignored.
        string command = _commandLine.Argument(0);

        // Now we must validate that the first argument is actually specified, 
        // then attempt to find the matching command delegate.
        if (command == null)
        {
            Echo("No command specified");
        }
        else if (_commands.TryGetValue(_commandLine.Argument(0), out commandAction))
        {
            // We have found a command. Invoke it.
            commandAction();
        }
        else
        {
            Echo($"Unknown command {command}");
        }
    }
}
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