Update

Author: danrega

02_Structures.md

@@ -15,6 +15,7 @@
     - [Creating Anonymous Structures](#creating-anonymous-structures)
   - [Variants of Structures](#variants-of-structures)
   - [Accessing (Components of) Structures](#accessing-components-of-structures)
+    - [ASSIGN Statements](#assign-statements)
   - [Populating Structures](#populating-structures)
     - [Using the VALUE Operator](#using-the-value-operator)
     - [Using the NEW Operator](#using-the-new-operator)
@@ -462,6 +463,102 @@ Nested components can be addressed using chaining:
 
 <p align="right"><a href="#top">⬆️ back to top</a></p>
 
+### ASSIGN Statements
+
+```abap
+"A field symbol is set using an assignment of a memory area to the 
+"field symbol by ASSIGN statements.
+"Particularly, field symbols and ASSIGN statements are supporting elements for 
+"dynamic programming. ASSIGN statements have multiple additions. Find more information 
+"and examples in the Dynamic Programming cheat sheet.
+
+TYPES: BEGIN OF s,
+         comp1 TYPE i,
+         comp2 TYPE c LENGTH 3,
+         comp3 TYPE n LENGTH 5,
+         comp4 TYPE string,
+       END OF s.
+
+DATA(demo_struc) = VALUE s( comp1 = 1 comp2 = 'abc' comp3 = '12345' comp4 = `ABAP` ).
+
+"Defining a field symbol
+FIELD-SYMBOLS <a> TYPE s.
+
+"Assigning the entire structure to a field symbole
+ASSIGN demo_struc TO <a>.
+
+"Accessing a structure component via the field symbol
+DATA(comp1) = <a>-comp1.
+
+"Field symbol declared inline
+"Note: The typing depends on the memory area specified. In this case,
+"the field symbol <fd> has the structured type s. This is valid for static
+"assignments. In case of dynamic assignments, the type is the generic type
+"data.
+ASSIGN demo_struc TO FIELD-SYMBOL(<b>).
+comp1 = <b>-comp1.
+
+"Accessing components of structures by assigning components to field symbols
+"The field symbols is typed with the generic type data so that all components,
+"which have random types, can be assigned.
+FIELD-SYMBOLS <d> TYPE data.
+ASSIGN demo_struc-comp1 TO <d>.
+ASSIGN demo_struc-comp2 TO <d>.
+ASSIGN demo_struc-comp3 TO <d>.
+ASSIGN demo_struc-comp4 TO <d>.
+
+"Accessing structures and components dynamically
+"Note: In case of dynamic assignments, ...
+"- sy-subrc is set.
+"- the type of field symbols declared inline is the generic type data.
+ASSIGN ('DEMO_STRUC') TO FIELD-SYMBOL(<c>).
+ASSERT sy-subrc = 0.
+
+"Using ASSIGN COMPONENT statements
+"It is recommended to use the newer syntax, which sepcifies the component 
+"selector followed by a data object in a pair of parentheses.
+"After COMPONENT (and in the parentheses in the newer syntax), a character-like 
+"or numeric data object is expected.
+DATA(some_comp) = `COMP2`.
+ASSIGN COMPONENT some_comp OF STRUCTURE demo_struc TO <d>.
+ASSERT sy-subrc = 0.
+
+some_comp = `COMP5`.
+ASSIGN COMPONENT some_comp OF STRUCTURE demo_struc TO <d>.
+ASSERT sy-subrc = 4.
+
+"Numeric data objects
+"The data object is implicitly converted to type i (if required) and
+"interpreted as the position of the component in the structure.
+ASSIGN COMPONENT 1 OF STRUCTURE demo_struc TO <d>.
+ASSERT sy-subrc = 0.
+
+ASSIGN COMPONENT 5 OF STRUCTURE demo_struc TO <d>.
+ASSERT sy-subrc = 4.
+
+"0 means that the entire structure is assigned
+ASSIGN COMPONENT 0 OF STRUCTURE demo_struc TO <d>.
+ASSERT sy-subrc = 0.
+ASSERT <d> = demo_struc.
+
+"Newer syntax using the component selector followed by content in
+"a pair of parentheses.
+ASSIGN demo_struc-('COMP4') TO <d>.
+ASSIGN demo_struc-(some_comp) TO <d>.
+ASSIGN demo_struc-(3) TO <d>.
+ASSIGN demo_struc-(0) TO <d>.
+
+"Iterating across all structure components
+DO.
+  ASSIGN demo_struc-(sy-index) TO <d>.
+  IF sy-subrc <> 0.
+    EXIT.
+  ENDIF.
+ENDDO.
+``` 
+
+<p align="right"><a href="#top">⬆️ back to top</a></p>
+
 ## Populating Structures 
 
 You can copy the content of a structure to another using the [assignment operator](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenassignment_operator_glosry.htm) `=`. 
@@ -1090,7 +1187,7 @@ ENDLOOP.
 - More information about the purpose of the individual components is available at [ABAP System Fields (F1 documentation for Standard ABAP)](https://help.sap.com/doc/abapdocu_latest_index_htm/latest/en-US/index.htm?file=abensystem_fields.htm).
 
 
-The following example demonstrates a selection of ABAP system fields. It uses artifacts from the ABAP cheat sheet repository. Note the comments in the code because a syntax warning will be displayed when inserting the code in a demo class that uses ABAP for Cloud Development. It is meant to emphasize that multiple system fields should not to be used in ABAP for Cloud Development.  
+The following example demonstrates a selection of ABAP system fields. It uses artifacts from the ABAP cheat sheet repository. Note the comments in the code because a syntax warning will be displayed when inserting the code in a demo class that uses ABAP for Cloud Development. It is meant to emphasize that multiple system fields should not be used in ABAP for Cloud Development.  
 To try the example out, create a demo class named `zcl_demo_abap` and paste the code into it. After activation, choose *F9* in ADT to execute the class. The example is set up to display output in the console. 
 
 ```abap

04_ABAP_Object_Orientation.md

@@ -4371,7 +4371,7 @@ Global class
  <td> 
 
 ``` abap
-CLASS zcl_some_class DEFINITION
+CLASS zcl_demo_abap DEFINITION
   PUBLIC
   FINAL
   CREATE PUBLIC .
@@ -4383,7 +4383,7 @@ CLASS zcl_some_class DEFINITION
   PRIVATE SECTION.
 ENDCLASS.
 
-CLASS zcl_some_class IMPLEMENTATION.
+CLASS zcl_demo_abap IMPLEMENTATION.
   METHOD if_oo_adt_classrun~main.
 
     "Object reference variables
@@ -4629,7 +4629,7 @@ Global class
  <td> 
 
 ``` abap
-CLASS zcl_some_class DEFINITION
+CLASS zcl_demo_abap DEFINITION
   PUBLIC
   FINAL
   CREATE PUBLIC .
@@ -4641,7 +4641,7 @@ CLASS zcl_some_class DEFINITION
   PRIVATE SECTION.
 ENDCLASS.
 
-CLASS zcl_some_class IMPLEMENTATION.
+CLASS zcl_demo_abap IMPLEMENTATION.
   METHOD if_oo_adt_classrun~main.
 
     "Object reference variables

06_Dynamic_Programming.md

@@ -319,6 +319,7 @@ FIELD-SYMBOLS:
   <simple>         TYPE simple, "Elementary data type including enumerated types and
                                 "structured types with exclusively character-like flat components
   <object>         TYPE REF TO object. "object can only be specified after REF TO; can point to any object
+                                       "The types REF TO object and REF TO data are considered complete types.
 
 "Data objects to work with
 DATA: BEGIN OF s,
@@ -428,6 +429,7 @@ ASSIGN s-structure TO <simple>.
 ASSIGN s-xl1 TO <simple>.
 "ASSIGN s-tab_ha TO <simple>.
 
+s-oref = NEW cl_system_uuid( ).
 ASSIGN s-oref TO <object>.
 ```
 
@@ -459,15 +461,20 @@ ASSIGN s-oref TO <object>.
 #### Declaring Data Reference Variables
 
 ``` abap
-"Example declarations of data reference variables with static types.
-"The static types can be complete or generic (but only data can be used). 
-"Note that they do not yet point to a data object. At this stage, 
-"initial reference variables contain null references.
+"The following example shows a selection of declaration options with data reference 
+"variables with static types. The static types can be complete or generic (but 
+"only data can be used). 
+"Note that the variables do not yet point to a data object. At this stage, 
+"initial reference variables contain null references. 
+DATA num type i.
+
 DATA: ref_a TYPE REF TO i,                 "Complete data type
-      ref_b TYPE REF TO some_dbtab,        "Complete data type
-      ref_c LIKE REF TO some_data_object,
+      ref_b TYPE REF TO zdemo_abap_carr,   "Complete data type
+      ref_c LIKE REF TO num,
       ref_d TYPE REF TO data,              "Generic data type
-      ref_e LIKE ref_a.                    "Referring to an existing data reference variable                  
+      ref_e LIKE ref_a,                    "Referring to an existing data reference variable
+      ref_f TYPE TABLE OF REF TO i,        "Reference table, complete data type
+      ref_g TYPE TABLE OF REF TO data.     "Reference table, generic data type                 
 ```
 
 As shown below, instead of the explicit declaration, inline declarations are also possible. 
@@ -1047,6 +1054,7 @@ DATA(idx) = line_index( dref->*[ ('CARRID') = 'LH' ] ).
 Some example contexts of using data references are as follows:
 
 *Overwriting data reference variables*:
+
 ``` abap
 DATA dref TYPE REF TO data.
 dref = NEW i( 1 ).
@@ -1108,6 +1116,7 @@ READ TABLE fli_tab INDEX 1 REFERENCE INTO DATA(rt_ref).
 ```
 
 *Data reference variables as part of structures and internal tables*:
+
 ``` abap
 "Unlike field symbols, data reference variables can be used as
 "components of structures or columns in internal tables.
@@ -1129,6 +1138,19 @@ APPEND struc TO itab.
 itab[ 1 ]-ref->* = 123.
 ```
 
+*Internal tables of type REF TO data can contain any data references*:
+
+```abap
+DATA it_ref TYPE TABLE OF REF TO data.
+
+"Such a table can hold any data type
+it_ref = VALUE #( ( NEW i( 3 ) ) "Elementary type
+                  ( NEW string( `hello` ) ) "Elementary type
+                  ( NEW zdemo_abap_flsch( carrid = 'XY' connid = '1234' ) ) "Structured type
+                  ( NEW string_table( ( `a` ) ( `b` ) ( `c` ) ) ) "Table type
+                ).
+```
+
 > **✔️ Hint**<br>
 > When to actually use either a field symbol
 or a data reference variable? It depends on your use case. However, data
@@ -2309,8 +2331,7 @@ ENDCLASS.
 
 ### Dynamic Method Calls
 
-
-- The following code snippet shows dynamically specifying method calls.
+- The following code snippet shows dynamically specifying method calls. Find three example classes below the syntax pattern snippet.
 - The snippet covers methods. Dynamic method calls require `CALL METHOD` statements. 
 - Find an example of a dynamic function module call - as another example of [procedure](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenprocedure_glosry.htm "Glossary Entry") calls - in the [Program Flow Logic](./13_Program_Flow_Logic.md#function-module-example) cheat sheet.
 
@@ -2359,7 +2380,14 @@ CALL METHOD class=>(meth) PARAMETER-TABLE ptab.
 "The addition EXCEPTION-TABLE for exceptions is not dealt with here.
 ```
 
-**Example class 1** 
+
+**Click to expand the expandable sections for example code**
+
+<details>
+  <summary>🟢 Example class 1</summary>
+  <!-- -->
+
+<br>
 
 The following example class explores dynamic method calls with simple methods. You can create a demo class called `zcl_demo_abap` and copy and paste the following code. Once activated, you can choose *F9* in ADT to run the class. The example is not designed to display output in the console.
 
@@ -2547,8 +2575,16 @@ CLASS zcl_demo_abap IMPLEMENTATION.
 ENDCLASS.
 ```
 
+</details>  
+
+<br>
+
+<details>
+  <summary>🟢 Example class 2</summary>
+  <!-- -->
+
+<br>
 
-**Example class 2** 
 
 The following simplified example highlights several things in the context of a dynamic method call example: 
 - Dynamic method call and assigning actual parameters to formal parameters statically
@@ -2624,6 +2660,110 @@ CLASS zcl_demo_test IMPLEMENTATION.
 ENDCLASS.
 ```
 
+</details>  
+
+<br>
+
+<details>
+  <summary>🟢 Example class 3</summary>
+  <!-- -->
+
+<br>
+
+The following example demonstrates dynamic method calls with methods defined in interfaces.
+
+<table>
+
+<tr>
+<td> Class include </td> <td> Code </td>
+</tr>
+
+<tr>
+<td> 
+
+Global class
+
+ </td>
+
+ <td> 
+
+``` abap
+CLASS zcl_demo_abap DEFINITION
+  PUBLIC
+  FINAL
+  CREATE PUBLIC .
+
+  PUBLIC SECTION.
+    INTERFACES if_oo_adt_classrun.
+  PROTECTED SECTION.
+  PRIVATE SECTION.
+ENDCLASS.
+
+CLASS zcl_demo_abap IMPLEMENTATION.
+  METHOD if_oo_adt_classrun~main.
+
+    "Creating an instance of the local class that implements
+    "an interface
+    DATA(oref) = NEW lcl( ).
+
+    "Static method call
+    DATA(number) = oref->lif~get_number( ).
+    out->write( number ).
+
+    "Dynamic method call
+    "Note the uppercase.
+    TRY.
+        CALL METHOD oref->('lif~get_number') RECEIVING number = number.
+        out->write( number ).
+      CATCH cx_sy_dyn_call_illegal_method INTO DATA(error).
+        DATA(error_text) = error->get_text( ).
+        out->write( error_text ).
+    ENDTRY.
+
+    CALL METHOD oref->('LIF~GET_NUMBER') RECEIVING number = number.
+    out->write( number ).
+  ENDMETHOD.
+ENDCLASS.
+``` 
+
+ </td>
+</tr>
+
+<tr>
+<td> 
+
+CCIMP include (*Local Types* tab in ADT)
+
+ </td>
+
+ <td> 
+
+``` abap
+INTERFACE lif.
+  METHODS get_number RETURNING VALUE(number) TYPE i.
+ENDINTERFACE.
+
+CLASS lcl DEFINITION.
+  PUBLIC SECTION.
+    INTERFACES lif.
+ENDCLASS.
+
+CLASS lcl IMPLEMENTATION.
+  METHOD lif~get_number.
+    number = cl_abap_random_int=>create( seed = cl_abap_random=>seed( )
+                                         min  = 1
+                                         max  = 1000 )->get_next( ).
+  ENDMETHOD.
+ENDCLASS.
+``` 
+
+ </td>
+</tr>
+
+</table>
+</details>  
+
+
 <p align="right"><a href="#top">⬆️ back to top</a></p>
 
 ### Dynamic Function Module Calls