Programming In Another Dimension

By Joe Pillera, MacTutor Contributing Editor, The Environmental Research Institute of Michigan

Programming In Another Dimension

Introduction. As software development systems evolve, there is always a increasing level of abstraction away from the machine - and to the problem domain of the user. One tool for the Macintosh that exemplifies this is the 4th Dimension® (4D1) from Acius. 4D is an incredible tool, because it goes far beyond a database: rather than just producing GUI (graphical user interface) skeletons like other programs, 4D can generate finished, ready to ship programs, complete with all the necessary Macintosh user interface controls.

This is the story of MacTutor Phone Book (MTPB), a complete 4D program (which is a stand-alone Macintosh application when compiled with the 4D compiler) which features:

• Complete support of the Macintosh interface, including pull down menus, desk accessory support, modeless dialog boxes, and printing.

• Searching, sorting and printing of address labels.

Background.

When constructing MTPB, I wanted more than a flat-file database: I wanted an application that could stand alone by itself. While a phone book application may not be as exotic as killing viruses, it serves as a good example of what 4D is capable of; without it, I would have faced the prospect of writing thousands of lines of code, and undoubtedly reinventing the wheel several times in the process.

Developing in 4D. The first aspect to developing in 4D is to specify the table structures, and use the layout editor to paint your user interface. As can be seen in Figures 1 and 2, 4D gives you a rich set of GUI controls to design the look and feel of your program.

Figure 1. Construction a MTPB input disalog with the 4D layout editor

Figure 2. The repetoire of user interface controls available for a custom 4D application.

Once the database structures and your custom windows have been designed, the fun starts. 4D gives you a comprehensive script language to implement custom applications, and even comes with a symbolic debugger, as illustrated in Figure 3. This script language is very pascal-like (minus the Unit module encapsulation feature), and includes features such as arrays, functions and procedures (a 4D function is a procedure that returns a value in the variable $0), pointer manipulation, and string manipulation that reminds me of BASIC (BASIC has one of the richest string manipulation syntaxes available).

Figure 3. Debugging a 4D procedure.

After your application has been designed, you can compile it with the 4D Compiler, as illustrated in Figure 4.

Figure 4. How to build a stand-alone application out of MTPB with the 4D Compiler

MacTutor Phone Book. Refer to Figure 5: not only can MTPB manage your phone records - it’s a complete Macintosh application (when compiled with the 4D Compiler).

Figure 5. MTPB as a stand-alone Macintosh application.

Furthermore, one of the parallels between object oriented programming and 4D programming is that you can “inherit” functionality, without having to write any code to implement it. Refer to Figures 6 and 8: MTPB makes full use of searching, and label printing - but these are given to you by 4D, and not implemented by me. This kind of reuse of software allows you to concentrate on the problem at hand, rather than on implementing code that has been written many times before. When custom windows do need to be designed, they can be assembled very quickly with 4D’s layout editor, as illustrated in Figure 7.

Figure 6. Search for all addresses that are either in Ann Arbor or whose last name field starts with 'P'.

Figure 7. Sorting in MTPB with a custom dialog constructed with the 4D layout editor.

Figure 8. Printing labels with MTPB.

Suggestions for Improvement.

While 4D is an incredibly powerful tool, I would like to suggest two possible future improvements:

Hierarchical menus: would be very useful in the menu editor, and would allow for a more concise construction of 4D applications.

Procedure abstraction: in a large 4D application, it is easy to get buried by a plethora of “global procedures.” What would be extremely useful here is some sort of hierarchical way of cataloging procedures. For example, introducing a “module” concept (containing procedures with scope only visible to it) would make organizing your 4D code a lot easier.

The End... Please note that this month’s source code disk contains only the data files for MTPB - and not a stand-alone program. Because of licensing rules, you’ll need to compile it with your own copy of the 4D Compiler - and a 4D Runtime module - before ending up with a double-clickable application.

The technical support at Acius is outstanding, and the software very thorough. Compared to other development tools which also hammer out skeleton user interfaces, there’s no doubt that 4D costs more. But that age-old adage still applies here.

You get what you pay for.

Joe Pillera is a research scientist at the Environmental Research Institute of Michigan (ERIM) in Ann Arbor, Michigan. The opinions expressed here are solely those of Joe Pillera, and not of ERIM or its affiliates. The author can be reached electronically via the GEnie2 service by sending mail to JPILLERA.

1 4D is a registered trademark of Acius, Inc.

2 GEnie is a trademark of the General Electric Company.

Global Procedures for MTPB
© MacTutor Magazine, February 1991


f_format_number
 ‘Pretty-process a phone number
 ‘Examples: 
 ‘format_number(“3131234567”)->(313)123-4567
 ‘format_number(“3131234567”;”313")->123-4567
 ‘Arguments:$1 = raw phone number
 ‘ $2 = area code to drop, if any.
 ‘Return Value: $0 = formatted result.
If (Length($1)>0)
 If (Length($2)=3)
 ‘The caller wants to zap an area code...
 If (Substring($1;1;3)=$2)
 ‘Omit the area code    
 $0:=Substring($1;4;3)+ “-” +
 Substring($1;7;4)
 Else 
 ‘Keep it    
 $0:=”(“+Substring($1;1;3)+”) “ +
 Substring($1;4;3) + “-” +
 Substring($1;7;4)
    End if 
  Else 
 ‘Caller wants the area code no matter what
 $0:=”(“ + Substring($1;1;3)+”)” + 
 Substring($1;4;3) + “-” +
 Substring($1;7;4)
  End if 
End if 


p_display
‘Display all records in the phone book
DEFAULT FILE([Phone Book])
ALL RECORDS
OUTPUT LAYOUT([Phone Book];”Output Layout”)
MODIFY SELECTION


p_print_sel
‘Print the records last selected by the user
DEFAULT FILE([Phone Book])
If (Records in selection=0)
 ALERT(“You haven’t selected any records
   to print!”)
Else 
 OUTPUT LAYOUT([Phone Book];”Output Layout”)
 PRINT SELECTION([Phone Book])
End if 


p_print_tbl
‘Print all records in the phone book
DEFAULT FILE([Phone Book])
ALL RECORDS
OUTPUT LAYOUT([Phone Book];”Output Layout”)
PRINT SELECTION([Phone Book])


p_search
‘Let the user perform a search on the database
DEFAULT FILE([Phone Book])
SEARCH
If (OK=1)
 OUTPUT LAYOUT([Phone Book];”Output Layout”)
 DISPLAY SELECTION
End if 


p_sort
‘Permanently sort the database, and display
‘results to the user.
DEFAULT FILE([Phone Book])
OPEN WINDOW(110;100;390;260;0;”Sort The Database”)
DIALOG(“Sort Dialog”)
‘Note: the actual sorting takes place in the script
‘      associated with the “ok” button, but is
‘      omitted here for brevity.
CLOSE WINDOW
If (g_display=True)
  p_display 
End if 


p_labels
DEFAULT FILE([Phone Book])
ALL RECORDS
PRINT LABEL([Phone Book];” “)


p_new
‘Add new records(s) until the user cancels
DEFAULT FILE([Phone Book])
INPUT LAYOUT([Phone Book];”Input Layout”)
Repeat 
 ADD RECORD
Until (OK=0)