Implementing the function class

Java™ class extending from function

Under the src folder of the plug-in project, create a Java™ class that extends from com.ghc.ghTester.expressions.Function. For example, com.samples.functions.FormatDate.

Implement the following methods:

• The default public constructor
• create(int, Vector)
• evaluate(Object)

Default constructor

Create a default public constructor with an empty body. You can add other initialization as required, but it does not have to do anything, by default. The default constructor must be public because of the way the functions are created.

public FormatDate() {
}

Override create (int size, Vector) parameters

The create(int, Vector) method is a factory method that creates an instance of the particular function with the parameters provided. The vector of parameters needs to be treated as functions themselves and are likely to be processec at run time.

public Function create(int size, Vector params) {
   Function outputFormat = null;
   if (size == 3) {
      outputFormat = (Function) params.get(2);
   }
   return new FormatDate((Function) params.get(0), (Function) params
                  .get(1), outputFormat);
}

The three-argument constructor that is used in the example can be found in the source that is provided in the examples folder of the Test Integrations and APIs installation folder.

Override evaluate(Object) data

The evaluate(Object) method performs the actual work of the function. Test Integrations and APIs passes the context of the current evaluation to your function. You can use this method to obtain the result from embedded functions and then return your functions own result.

public Object evaluate(Object data) {
   String date = m_fDate.evaluateAsString(data);
   String inputFormat = m_fInputFormat.evaluateAsString(data);
   String outputFormat = "yyyy-MM-dd"; // Default format
      if (m_fOutputFormat != null) {
   outputFormat = m_fOutputFormat.evaluateAsString(data);
   }

   //...
   if (EvalUtils.isString(date)) {
      date = EvalUtils.getString(date);
   }
   if (EvalUtils.isString(inputFormat)) {
      inputFormat = EvalUtils.getString(inputFormat);
   }
   if (EvalUtils.isString(outputFormat)) {
      outputFormat = EvalUtils.getString(outputFormat);
   }

   SimpleDateFormat inputFormatter = new 
SimpleDateFormat(inputFormat);
   String formattedDate = "";
   try {
      Date d = inputFormatter.parse(date);
      SimpleDateFormat outputFormatter =new 
SimpleDateFormat(outputFormat);
      formattedDate = outputFormatter.format(d);
   } catch (ParseException ex) {
      // ...
   }

   return "\"" + formattedDate + "\"";
}