Identify classes in the Progress.Reflect package

A number of the PUBLIC methods of Progress.Lang.Class use classes in the Progress.Reflect package both as parameters and as a way of returning information. The "Get" reflection methods return instances of classes to describe class members. For example, if you call GetMethod( ) to get information about a particular method of a class, GetMethod( ) returns an instance of Progress.Reflect.Method representing the method. The following table describe some of the public properties of Progress.Reflect.Method.

As mentioned in the table, Progress.Reflect.AccessMode is a built-in enumeration type. For more information about working with ABL enumeration types, see the ENUM statement entry in ABL Reference.

Progress.Reflect.Method also provides methods, including an Invoke( ) method (with overrides for both static and instance methods) that allows you to call the method that the Progress.Reflect.Method instance represents. This is the syntax for the instance method override:

Invoke ( INPUT instance AS Progress.Lang.Object,
         INPUT params AS Progress.Lang.ParameterList )

This override takes an instance of the class that implements the method and a parameter list to hold the parameters that are passed to the method.

The following code uses reflection methods to add two pieces of data to a JSON array and then write that array to a file, following these steps:

1. GetClass( ) is invoked statically to create plcjArray, a Progress.Lang.Class instance representing a Progress.Json.ObjectModel.JsonArray object. The GetConstructor( ) method of Progress.Lang.Class is invoked to create jArray, an instance of JsonArray.
2. GetMethod( ) is invoked on plcjArray to create myMethod, an instance of Progress.Reflect.Method, which in this case represents the Add( ) method of JsonArray. Then Invoke( ) is called on myMethod, which invokes Add( ) to add the character data to jArray.
3. After getting the method again using a revised parameter list, Invoke( ) is called on myMethod to add the date to jArray.
4. GetMethod( ) is invoked again on plcjArray, this time to create an instance of Progress.Reflect.Method that represents the WriteFile( ) method of JsonArray. Invoke( ) is called on myMethod to write jArray to file.

/* Use GetMethod() and Invoke() to add data to a JsonArray */
USING Progress.Json.ObjectModel.* FROM PROPATH.
USING Progress.Reflect.*.

VAR Progress.Lang.Class plcjArray.
VAR Constructor myConstructor.
VAR Method myMethod.
VAR CLASS JsonArray jArray.
VAR Progress.Lang.Parameterlist myPL.

VAR CHAR char1 = "Mr. Smith".
VAR DATE date1 = 11/16/2010.

/* 1. Create a JsonArray object. */
plcjArray = 
   Progress.Lang.Class:GetClass("Progress.Json.ObjectModel.JsonArray").
myPL = NEW Progress.Lang.Parameterlist(0).
myConstructor = plcjArray:GetConstructor(myPL).
jArray = CAST(myConstructor:Invoke(myPL), Progress.Json.ObjectModel.JsonArray).

/* 2. Get and invoke Add( ) to add the name. */
myPL = NEW Progress.Lang.Parameterlist(1). 
myPL:SetParameter(1, "CHARACTER", "INPUT", char1).
myMethod = plcjArray:GetMethod("Add", myPL).              
myMethod:Invoke(jArray, myPL).

/* 3. Get and invoke Add( ) again to add the date */  
myPL:SetParameter(1, "DATE", "INPUT", date1).
myMethod = plcjArray:GetMethod("Add", myPL). 
myMethod:Invoke(jArray, myPL).

/* 4. Get and invoke WriteFile( ). */
myPL = NEW Progress.Lang.Parameterlist(2). 
myPL:SetParameter(1, "CHARACTER", "INPUT", "filename.json").
myPL:SetParameter(2, "LOGICAL", "INPUT", TRUE).
myMethod = plcjArray:GetMethod("WriteFile", myPL).
myMethod:Invoke(jArray, myPL).

For full descriptions of the properties and methods of Progress.Reflect.Constructor, Progress.Reflect.Method, Progress.Reflect.Event, Progress.Reflect.Property, and Progress.Reflect.Variable, see their entries in ABL Reference.