ESL Unit Event

Esl UNIT is an object of EVENT type. It enables to configure the universal scripts with the procedures and variables and use them in ESL scripts (as the libraries). There are available only those procedures that are defined by the enumerated word PUBLIC. You may use all available ESL actions and functions in UNIT. The only difference from the ESL script is that there cannot be defined the RPC procedures and ESL Interface in UNIT.

Each UNIT declaration in the script causes that there is created the new object with its own local variables and procedures in the system. This is the main difference from #include in C, where #include inserts whole text of the library, which contains the declaration of functions, to the script. This feature enables to define of more UNIT of the same type in the script. Each UNIT may have the different values of its local variables (each UNIT has its own life cycle).

The life cycle of UNIT is limited by the duration of a life cycle of script, which is declared and used by the given UNIT, in the system. The life cycle of UNIT begins its declaration in the script and ends when the script, in which UNIT had been declared, is terminated in the system.

The addressing of the Public procedure of UNIT means the calling of the procedure of a particular UNIT by the local variable, which represents it. The procedures can be called only from the script that declares the given UNIT.

It is possible to send the identifiers of all objects used in the ESL script that declares the given UNIT to the Public procedures defined within the UNIT - handles of open files, containers, JSON and XML files, transactions and other database operations.

Configuration

The UNIT is configured in the configuration dialog box in the D2000 CNF. Create UNIT as a new object of EVENT type. When creating, the script editor is opened automatically. There, click the  Parameters button to open the configuration dialog box. Select the option Unit event on the Parameters tab.

A parent of UNIT can be any process of *.EVH. UNIT event is not activated when starting the process. The configuration of the script in ESL UNIT is the same as in other types of events. There are used all properties of ESL language.

Exceptions:

• It contains the keyword PUBLIC.
• The RPC procedures and ESL Interface may not be defined.

The initial part of the script (between BEGIN - END) is always executed. The actions in the UNIT script are executed in the context of an instance of ESL script, in which the UNIT is declared. The UNIT event does not allow debugging. The debugging procedure is described in the section Debugging the UNIT scripts.

Example:

 ;*********************************************************
 ; DESCRIPT: Unit1 - Counter
 ; 
 ; 
 ; AUTHOR: Programmer 
 ; LAST CHANGE: 
 ;********************************************************* 
 
 
 INT _iLocal
 ;
 PUBLIC PROCEDURE Make
  _iLocal := _iLocal + 1
 END Make
 
 PUBLIC PROCEDURE GetValue(INT _iValue)
 _iValue := _iLocal
 END GetValue
 
 BEGIN
  _iLocal := 0
 END 

Declaration and usage of UNIT

  UNIT (Name_of_unit_event) _unit1

The declaration of a local variable of UNIT type must always be at the beginning of the ESL script.
When starting the script with UNIT declarations, the initial parts of these UNITs are executed in the order as they are declared. If the declaration of the local variables contains more UNITs of the same type, the initial part of all ones will be executed.
There is supported the declaration of UNIT in UNIT, which uses the features of UNIT in other UNIT. For this feature, there is supported detection of UNIT deadlock.

The calling of Public procedures is done by CALL action. After this action, there must be an addressee (_unit1), which contains the given PUBLIC procedure.

  CALL [_unit1] Make
  CALL [_unit1] GetValue(_value) 

The operation is done by switching the context. Then the called procedure is done and the context is switched back (the executing of the original script).

Note: The addressee [_unit1] must always be the name of the local variable that has been used in the UNIT declaration.

Example:

 ;*********************************************************
 ; DESCRIPT: Unit Caller
 ; 
 ; 
 ; AUTHOR: Programmer
 ; LAST CHANGE:
 ;********************************************************* 
 
 UNIT (E.Unit1) _unit1
 UNIT (E.Unit1) _unit12
 UNIT (E.Unit2) _unit2
 
 RPC PROCEDURE CheckValue(BOOL _bOk)
 INT _iValue
 INT _iValue2
 
 CALL [_unit1] GetValue(_iValue)
 CALL [_unit12] GetValue(_iValue2)
 
 _bOk := _iValue # _iValue2
 
 END CheckValue
 
 BEGIN
 
  CALL [_unit1] Make
  CALL [_unit12] Make
  CALL [_unit12] Make 
 
 END

As each declared UNIT has its own life cycle, this ensures that you may declare 1 up to n UNITs of the same type in one script (e.g. _unit1 and _unit12 are of the same type E.Unit1). It means, the UNITs of the same type may have different values of the local variables after the different operations.

Debugging the UNIT scripts

ESL Unit is debugged together with the script in which it is declared.

If you use the debugging Step Into (F8 - Stepping with the nesting), the tab with the UNIT script is automatically opened in ESL editor and the currently executed line is set. When debugging the script that contains the declarations of UNITs of the same type, the ESL editor opens as many tabs with UNIT scripts as necessary.

After finishing the UNIT script, the tab is switched back to the script, which is called the UNIT. After debugging the script, the ESL editor automatically closes all the UNIT tabs, which were used.