Procedure Parameters
Introduction
To define parameters, use the Procedure Parameters form, a sub-level of the Procedure Stepsform (itself a sub-level of the Procedure Generator).
Most procedure steps incorporate parameters. These are a means of transferring arguments from the procedure to programs or reports activated by the procedure. They also serve to transfer information from one procedure step to another (or from the user to the procedure step).
Example:When a program finds an error, it writes the appropriate message to a file (i.e., a parameter in the program). The parameter is then passed on to the PRINTERR command, which prints out its contents on screen.
Only certain steps require parameter specification (e.g., CONTINUE and END do not). Moreover, different types of steps require that different attributes of the parameter be defined. For instance, you need not specify type for any parameter in a CHOOSE or CHOOSEF command, and there is no need to designate position for any parameters in a report step.
Parameter Name and Title
All procedure parameters must be given a name. This must meet the same requirements as the procedure name, with two exceptions: (1) there is no prefix); and (2) the parameter name is restricted to up to three characters (e.g., DAY, MSG, AA).
The title is a short description of the parameter. When the parameter is for input purposes or generates a Choose menu, the user will see the title. It can also be used to store a brief message that is displayed by the PRINT, PRINTCONT or PRINTERR command.
Parameter Order
The order of parameters in a given procedure step is determined by their position (an integer). Integers need not be consecutive; the parameter with the lowest integer will be first. In a program, parameter position will determine the order of parameters that are passed to the procedure.
Note: If the procedure step consists of a single parameter, it is not necessary to specify position at all. Nor is it necessary to indicate position for parameters in a report step.
Parameter Content
There are three distinct types of procedure parameters:
- Those which are constants or variables.
- Those which are text files.
- Those which are linked files.
A parameter may be assigned a constant value or a variable in the Value column. The value of any variable, which is identified by the prefix “:” (e.g., :date), must be specified earlier in the procedure.
The content of a text file is determined by a step in the procedure (generally by a program). This is generally a message file, which will then be printed out by a PRINT, PRINTCONT or PRINTERR command.
Note: All temporary text files created by the system (e.g., procedure message files) are saved in Unicode format.
A linked file is a copy of a database table that contains only certain records. This file includes all the table’s columns and keys. The content of a linked file is input by the user via a parameter input screen or by means of a form. Such a file is tied to a specific database table and column by means of the Table Name and Column Name columns. The user then retrieves specific records by specifying search criteria for the column in question, by moving from the column in the parameter input screen to a target form and retrieving desired records, or by retrieving data from the form that opens instead of the input screen (as a result of a Form step in the procedure). A third possibility is to input data from a specific form record. This occurs when the procedure is directly activated from within a given form. Whatever method is used, a file of records is created. Data manipulations may then be carried out on the linked file.
Parameter Type
With the exception of parameters for a CHOOSE or CHOOSEF command, all procedure parameters must have a specified type.
- A parameter which contains a constant value must be assigned one of the valid column types (CHAR, REAL, INT, UNSIGNED, DATE, TIME, DAY).
- A parameter that is a text file must be assigned ASCII type.
- A parameter that stores text must be assigned TEXT type.
- If the parameter is a linked file of records, you must designate one
of the following types and specify the names of the table and column
to which the file is linked:
- Select FILE if the linked file comprises a group of records input from the database.
- Select NFILE if the linked file comprises a group of records and you want the link table to remain empty when the user enters * or leaves the field empty.
- Select LINE if the file consists of a single record input from the database.