Dynamic Interface

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Dynamic Interface

The stubcode interface offers ease of use with Chameleon at the expense of flexibility. The dynamic interface offers an alternative to using stubcode, which gives more power but requires more effort on the part of the programmer. This table summarizes the main differences between the approaches:

	Dynamic Interface	Static Interface
Needs code generation?
Can the compiler find out the spelling mistakes?
Advantages	Message tables can be explored dynamically. Application can be delivered without stubcode.	Guaranteed to avoid the runtime problems caused by typos.
Disadvantages	Cannot avoid the problems caused by typos.	Application has to be delivered with stubcode.
Changing messages and table grammar	Do not need to recompile.	Need to recompile.

To use the dynamic interface to parse a message, the following steps must be followed:

Drop a TCHMdynamicEngine component on your form. This is required because it defines the ParseMessageDynamically method.
Load the message definition file.
Instantiate an empty TCHMdynamicMessage object.
Invoke ParseMessageDynamically to parse the message.
The resulting TCHMdynamicMessage object can then be explored using the methods defined from its parent TCHMcustomTable class.

The following code fragment shows the previous steps. For a complete example of the usage of the dynamic interface, you can look at the New Project Wizard labelled 'Dynamic' which makes a simple example project that uses the interface.

var
   Msg : string;
   MessageTable : TCHMdynamicMessage;
   MessageIndex : Integer;
begin
   // Load the message definition file 
   //(in a real world app we would do this in the FormCreate event).
   
   Engine.Load('project.vmd');
   
   // This is message begin parsed.
   Msg := 'MSH|^~\&|REGADT|MCM|RSP1P8|MCM|199601051530|SEC|ADT^A04|00000007|P|2.5' + #13;
   Msg := Msg + 'EVN|A44|199601051530' + #13;
   Msg := Msg + 'PID|||MR2^^^XYZ||JONES^WILLIAM^A^JR||19501010|M|||123 EAST STREET^^NY^NY^10021||(212)111-3333|||S||ACCT1' + #13;
   Msg := Msg + 'MRG|MR1^^^XYZ||ACCT1' + #13;

   MessageTable := nil;
   try
      MessageTable := TCHMdynamicMessage.Create(Engine);
      MessageIndex := Engine.ParseMessageDynamically(Msg, MessageTable);
      Engine.WriteToLog('Message name: ' + Engine.MessageName(MessageIndex));
      OutputTable('', MessageTable);
   finally
      MessageTable.Free;
   end;
   Engine.WriteToLog('');


	Have a good read of the documentation for the interface of the TCHMcustomTable object to understand how to navigate through it. Methods like ColumnName are handy for finding the indexes of columns. Also remember, you'll need to use the SubTable property to access the actual tables defined in the message since the top most table is the message itself.

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Dynamic Interface