Support of the Lazy Initialization Pattern for Arrarys

Author: aafent

FAST.FBasic.InteractiveConsole/Tests/ApplicationForm.bas

@@ -12,49 +12,22 @@ WORDEXTRACTBODY template, text   ' Templating Library
 
 rem Extract metadata
 PHVSDATA allNames text          ' TextReplacer Library
-PHSdata cnames text             ' TextReplacer Library
 
 rem Orchestrate the needed data 
 print "Load data on demand..."
 let AppID=1010  ' Input from the caller application
 let Today = date()
-
-foreach cnames 
-   loginfo "Setting up...."+[cnames.ph]
-   phgosub [cnames.ph] else notfound ' TextReplacer Library
-endforeach cnames
-
+retrieve Appl,NEW,1, "select CustomerID,RequestedAmount,LoanTerms,Purpose,ApplicationDate from Applications  where ApplicationID="+sql(AppID)   ' SQLData Adapter 
+retrieve Cust,NEW,1, "select Name,VatNumber,Email,Address,City from Customers where CustomerID="+sql([Appl.CustomerID])
 
 rem (v) Do the replacement and save the document
 loginfo "Creating the new document"
 WORDREPALCEBODY template, ALL, allNames   ' Templating Library
 
-
 rem (v) Append Consent 
 FILESTREAM Consent, in, "", "other", "Consent.docx"
 WORDAPPEND Consent, template
 
 SCOPY template,final    ' Streams Library
 
-halt
-
-rem
-rem ...............DATA SOURCES...................
-rem 
-Appl:
-loginfo "Loading Application: "+AppID
-retrieve Appl,NEW,1, "select CustomerID,RequestedAmount,LoanTerms,Purpose,ApplicationDate from Applications  where ApplicationID="+sql(AppID)   ' SQLData Adapter 
-
-return
-
-Cust:
-loginfo "Loading Customer:"+[Appl.CustomerID]
-retrieve Cust,NEW,1, "select Name,VatNumber,Email,Address,City from Customers where CustomerID="+sql([Appl.CustomerID])
-
-return
-
-notfound:
-print "***NOT FOUND***"
-return
-
 End

FAST.FBasic.LibraryToolkit/Types/FBasicArray.cs

@@ -7,6 +7,8 @@ public class FBasicArray : Types.JaggedArray2D<Value>, IBasicCollection
     {
         private string[] columnNames = new string[0];
 
+        public Action<object[]> LazyInitializingCallback = null!; 
+
         /// <summary>
         /// Default is false. If it is true, on delete row statement, the row order will prevented
         /// but the operation will be slow, as all the rows will shifted one up. 

FAST.FBasic.TemplatingLibrary/FBasicTemplatingLibrary.cs

@@ -356,7 +356,6 @@ private void WordReplaceBody(IInterpreter interpreter)
             var replacements=array.ConvertToDictionary<string,string>(0,1);
             foreach (var item in replacements)
             {
-                Console.WriteLine(item.Value);
                 replacements[item.Key] = ToolKitHelper.FormatStringValue(item.Key, interpreter.GetValue(item.Value).ToString());
             }
             new WordPlaceHolder(placeHolderPrefix,placeHolderSuffix).ReplacePlaceholders(((Stream)stream.Object), replacements, policy);

FAST.FBasicInterpreter/Core/Interpreter_Methods.cs

@@ -81,7 +81,14 @@ public FBasicArray GetArray(string name)
                 Error(Errors.E112_UndeclaredEntity("Array",name));
                 return null; // unnecessary but the compiler will like it...
             }
-            return this.arrays[name];
+            var array= this.arrays[name];
+            if (array.LazyInitializingCallback == null) return array;
+
+            // (v) init
+            array.LazyInitializingCallback(null); 
+            array.LazyInitializingCallback=null;
+
+            return array;
         }
 
         /// <summary>

FAST.FBasicInterpreter/DataProviders/sqlFBasicDataProvider.cs

@@ -152,6 +152,21 @@ public static void RETRIEVE(IInterpreter interpreter)
             interpreter.GetNextToken();
             string sql = interpreter.Expr().ToString();
 
+            // (v) add the array with lazy initializing method
+            FBasicArray array;
+            if (interpreter.IsArray(name))
+            {
+                array = interpreter.GetArray(name);
+            }
+            else
+            {
+                array = new();
+                interpreter.AddArray(name,array);
+            }
+            array.LazyInitializingCallback=(a)=>lazyRetrieve(interpreter, array, name, rowSet, maxRows, sql);
+            
+
+            /*
             // (v) do the statement
             var adapter = interpreter.GetDataAdapter<sqlFBasicDataProvider>(adapterName);
             IBasicCollection collection;
@@ -209,7 +224,7 @@ public static void RETRIEVE(IInterpreter interpreter)
 
                 interpreter.DropCollection(name);
             }
-
+            */
         }
         public static Value SQL(IInterpreter interpreter, List<Value> args)
         {
@@ -235,6 +250,58 @@ public static Value SQL(IInterpreter interpreter, List<Value> args)
         }
 
 
+        private static void lazyRetrieve(IInterpreter interpreter, FBasicArray array, string name, string rowSet, int maxRows, string sql)
+        {
+            // (v) do the statement
+            var adapter = interpreter.GetDataAdapter<sqlFBasicDataProvider>(adapterName);
+            IBasicCollection collection;
+            if (!adapter.cursors.ContainsKey(name))
+            {
+                adapter.cursors.Add(name, new() { sqlText = sql });
+                collection = new cursorCollection(name, adapter);
+                interpreter.AddCollection(name, collection);
+            }
+            else
+            {
+                adapter.cursors[name].sqlText = sql; //reset the sql command
+                collection = new cursorCollection(name, adapter);
+                collection.ClearCollection();
+            }
+            collection.MoveNext();
+
+            if (collection.Current is IDataRecord data)
+            {
+                if (rowSet == "NEW") array.ResetArray();
+
+                array.SetColumnNamesFrom(data);
+
+                int row;
+                if (rowSet == "APPEND")
+                {
+                    row = array.Length + 1;
+                }
+                else
+                {
+                    row = array.GetCurrentRow();
+                }
+
+                if (maxRows == 0) maxRows = int.MaxValue;
+                for (int times = 1; times <= maxRows; times++)
+                {
+                    for (int inx = 0; inx < array.ColumnNamesCount; inx++)
+                    {
+                        array[row - 1 + (times - 1), inx] = ToolKitHelper.ToValue(data[inx]);
+                    }
+
+                    collection.MoveNext();
+                    if (collection.endOfData) break; // stop early (before maxRow) as no more datas
+                }
+
+                interpreter.DropCollection(name);
+            }
+
+        }
+
     }
 
 }

FAST.FBasicInterpreter/ReleaseNotes.md

@@ -9,7 +9,8 @@ For **Business and Technical** documentation read the [Wiki page](https://github
 
 | When       | Description                                            |
 |------------|--------------------------------------------------------|
-| 2025-11-16 | New statement RETRIEVE for SQL Data Adapter            |
+| 2025-11-16 | Now Arrays supporting the Lazy Initialization Pattern           |
+| 2025-11-16 | New statement RETRIEVE for SQL Data Adapter using lazy initialization |
 | 2025-11-15 | New format specifier D for dates                       |
 | 2025-11-13 | Support for .Net.10.0                                  |
 | 2025-11-03 | New function singlewhite() to Text Replacer Library    |