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<html><title>The cConfig Class</title><body bgcolor="#FFFFFF" text="#000000" link="#0000AA" alink="#0000FF" vlink="#000044"><h2 align=center>The cConfig Class</h2><p>The cConfig class stores the values in <tt>genesis</tt> throughout arun. It is defined in the files"<tt>config.hh</tt>" and "<tt>config.cc</tt>" in the directory"<tt>current/source/main/</tt>". This is one of the rare classes thathas a longer class definition in the header file than that ofits individual methods in the code file. This is because so manymethods are accessor functions that are defined as they are declared.<p>Currently, this is a static class. That means there can never be an objectof type cConfig; there is only the class itself that exists. This comesfrom the idea that an avida run can only ever have a single configuration.However, ideally we should make it possible for multiple populations toco-exist, each with distinct configurations, so at some point in thefuture (when I get the energy, and don't have more pressing programmingissues!) I will convert this to a normal class type.<p>Here is a <i>heavily</i> abridged version of the class definition (from"<tt><b>config.hh</b></tt>").<p><pre> class <font color="#880000">cConfig</font> { private: static <font color="#880000">cString</font> <font color="#000088">event_filename</font>; static <font color="#880000">cString</font> <font color="#000088">analyze_filename</font>; static <font color="#880000">int</font> <font color="#000088">rand_seed</font>; static <font color="#880000">double</font> <font color="#000088">copy_mut_prob</font>; <font color="#886600">// [ <i>...about 100 other variables stored...</i> ]</font> <font color="#886600">// A method that will process the command line arguments</font> static void <font color="#008800">ProcessConfiguration</font>(<font color="#880000">int</font> <font color="#000088">argc</font>, <font color="#880000">char</font> * <font color="#000088">argv</font>[], <font color="#880000">cGenesis</font> & <font color="#000088">genesis</font>); public: <font color="#886600">// A method that will setup everything in cConfig</font> static void <font color="#008800">Setup</font>(<font color="#880000">int</font> <font color="#000088">argc</font>, <font color="#880000">char</font> * <font color="#000088">argv</font>[]); <font color="#886600">// Accessors...</font> static <font color="#880000">cString</font> & <font color="#008800">GetEventFilename</font>() { return <font color="#000088">event_filename</font>; } static <font color="#880000">cString</font> & <font color="#008800">GetAnalyzeFilename</font>() { return <font color="#000088">analyze_filename</font>; } static <font color="#880000">int</font> <font color="#008800">GetRandSeed</font>() { return <font color="#000088">rand_seed</font>; } static <font color="#880000">double</font> <font color="#008800">GetCopyMutProb</font>() { return <font color="#000088">copy_mut_prob</font>; } <font color="#886600">// [ <i>...about 100 other variable accessors...</i> ]</font> <font color="#886600">// Set Methods...</font> static void <font color="#008800">SetEventFilename</font>(const <font color="#880000">cString</font> & <font color="#000088">in_name</font>) { <font color="#000088">event_filename</font> = <font color="#000088">in_name</font>; } static void <font color="#008800">SetAnalyzeFilename</font>(const <font color="#880000">cString</font> & <font color="#000088">in_name</font>) { <font color="#000088">analyze_filename</font> = <font color="#000088">in_name</font>; } <font color="#886600">// [ <i>...again, many more set methods...</i> ]</font> };</pre><p>Note that there is no constructor or destructor since objects of cConfigare never created or destroyed. The <font color="#008800">Setup()</font>method will, however, setup any values that need to be handled.<h3>The <tt>config.cc</tt> file</h3><p>You will need to know about the code file for cConfig in order to make anyadditions to the class. The code file is broken up into three sections. Thefirst is a list of all of the variables declared inside of the classdefinition. In order for a variable to be static, it has to be declared inboth the class definition, and again outside the class in the code file. Theentire beginning of the code file is in the form:<p><pre> <font color="#880000">cString cConfig</font>::<font color="#000088">event_filename</font>; <font color="#880000">cString cConfig</font>::<font color="#000088">analyze_filename</font>; <font color="#880000">int cConfig</font>::<font color="#000088">rand_seed</font>; <font color="#880000">double cConfig</font>::<font color="#000088">copy_mut_prob</font>;</pre><p>Remember that a header file can be included inside of many other files sothat each of those know how to interact with this class. Well, the reasonfor this section of the code file is to make it clear to the compiler thatthis will be the main location to store the static variables associated withthis class. Normally variables setup when an object is created; since thereis no object, we must explicitly tell it to setup the variables.<p>After the long list of variable re-declarations, the next portion of thefile is the <font color="#008800">Setup</font>() method. Its body defines an object of class <font color="#880000">cGenesis</font>, and then uses it toload all of the individual variables that make up cConfig. Most of thismethod consists of lines in the form:<p><pre> <font color="#000088">event_filename</font> = <font color="#000088">genesis</font>.<font color="#008800">ReadString</font>("EVENT_FILE", "events.cfg"); <font color="#000088">analyze_filename</font> = <font color="#000088">genesis</font>.<font color="#008800">ReadString</font>("ANALYZE_FILE", "analyze.cfg"); <font color="#000088">world_x</font> = <font color="#000088">genesis</font>.<font color="#008800">ReadInt</font>("WORLD-X"); <font color="#000088">world_y</font> = <font color="#000088">genesis</font>.<font color="#008800">ReadInt</font>("WORLD-Y"); <font color="#000088">point_mut_prob</font> = <font color="#000088">genesis</font>.<font color="#008800">ReadFloat</font>("POINT_MUT_PROB"); <font color="#000088">copy_mut_prob</font> = <font color="#000088">genesis</font>.<font color="#008800">ReadFloat</font>("COPY_MUT_PROB");</pre><p>The final portion of the <tt>config.cc</tt> file consists of the method<font color="#008800">ProcessConfiguration</font>(), which handlesthe command line arguments entered by the user. This will, perhaps, be thetopic of another lesson.<h3>How to use the cConfig class</h3><p>Now that we know how the cConfig class works, we need to be able to useit from the rest of avida whenever we need it. This is very simple; to call a method on a static class from anywhere, all you need to do istype the class name, a double colon ('::') and then the method name thatyou wish to call.For an example that we've already seen, remember that the body of all of theinject events contained the line:<p><pre> if (<font color="#000088">fname</font> == "START_CREATURE") <font color="#000088">fname</font> = <font color="#880000">cConfig</font>::<font color="#008800">GetStartCreature()</font>;</pre><p>This line sets the inject organism filename to the one found in the cConfigclass if the name was otherwise set to be "START_CREATURE". To do this,we need to ask cConfig what the starting creature filename is. Fortunately,that's an easy thing to do.<h3>Adding a Genesis Variable: A Checklist</h3><p>We finally have all of the information of how a variable in the genesisfile is loaded, stored, and accessed when needed. However, this can bea lot to remember. Below is a checklist of all of the locations in thesource code that you would need to make a change when you want to performsuch a programming feat.<p><b>1. Add the variable to the private data of cConfig [in <tt>config.hh</tt>]</b> :This is the location that the variable is defined and stored overthe course of an avida run.<p><b>2. Add and accessor to the new data [<tt>config.hh</tt>]</b> : All variables must have a method that makes them accessible from the restof the source code.<p><b>3. Add a method to set a new value to the data [<tt>config.hh</tt>]</b> :This is optional. If the new variable can ever change during a run, theremust be a method in cConfig that causes that change.<p><b>4. List the variable in the code file. [<tt>config.cc</tt>]</b> :All variables must be listed a second time at the top of <tt>config.cc</tt>so that the single instance of them is actually created.<p><b>5. Load the variable in cConfig::Setup() [<tt>config.cc</tt>]</b> :This is where the value that is stored in the <tt>genesis</tt> configurationfile initializes the variable you've just added to cConfig.Remember to provide a default value in case the user leaves it out.<p><b>6. Use the variable wherever you need it!</b> :Your new variable is ready for you. Use it wisely.⌨️ 快捷键说明
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