Sams REALbasic cross platform application development apr 2006 ISBN 0672328135

Chapter 4 , Cross-Platform Application Development REALbasic gives you the capability to create applications forWindows, Macintosh, and Linux operating systems.. REALBASIC IS A MODERN, O

By Mark Choate

Publisher: Sams Pub Date: April 12, 2006 Print ISBN-10: 0-672-32813-5 Print ISBN-13: 978-0-672-32813-8 Pages: 672

out there Get inside this development environment with REALbasic Cross-Platform

Application Development.

By Mark Choate

Publisher: Sams Pub Date: April 12, 2006 Print ISBN-10: 0-672-32813-5 Print ISBN-13: 978-0-672-32813-8 Pages: 672

REALbasic CrossPlatform Application Development

Copyright © 2006 by Sams Publishing

All rights reserved No part of this book shall be reproduced,stored in a retrieval system, or transmitted by any means,

electronic, mechanical, photocopying, recording, or otherwise,without written permission from the publisher No patent

liability is assumed with respect to the use of the informationcontained herein Although every precaution has been taken inthe preparation of this book, the publisher and author assume

no responsibility for errors or omissions Nor is any liabilityassumed for damages resulting from the use of the informationcontained herein

regarded as affecting the validity of any trademark or servicemark REAL Software, REALbasic and the REAL Software cubelogo are registered trademarks of REAL Software, Inc

Every effort has been made to make this book as complete and

as accurate as possible, but no warranty or fitness is implied.The information provided is on an "as is" basis

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REALbasic to develop cross-platform tools for use in online

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I would be remiss if I also did not mention two people to whom

I am particularly indebted Both Connor Choate and ChristineGoertz Choate provided patient support while I wrote the book.They gave up more than a few weekends and vacations, andwithout their help I would not have been able to complete thisbook They both have my heartfelt thanks and sincere

appreciation

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and commentator We value your opinion and want to know

what we're doing right, what we could do better, what areasyou'd like to see us publish in, and any other words of wisdomyou're willing to pass our way

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IN A WORLD OF OPEN SOURCE OR FREELY available

programming languages and integrated development

environments, you might be wondering why you would want topurchase REALbasic, a proprietary language that is closed-

source and definitely not free I think there is a very good

reason to do sobecause REALbasic offers some unique

characteristics that cannot be found anywhere else First of all,it's remarkably easy to use It also compiles into native

machine code for three operating systems: Windows,

Macintosh, and Linux

REALbasic is a dynamic language REAL Software, the companythat produces REALbasic, releases a new version every six

months This means that new features are being added (and oldbugs are being fixed) all the time There is so much you can dowith REALbasic that it is impossible to cover it in one book, so Ihave tried to focus on the primary features of the language thatmost programmers will use Rest assured, however, that by thetime you read this, there will be more features available andstill plenty more to learn about

REALbasic also has a very active and friendly user community

If you have not done so already, it's a good idea to sign up forone of the mailing lists where users post questions and get

answers from other users as well as REALbasic engineers

themselves Throughout the years, I have been an avid reader

of the messages from these lists, and this book owes a debt ofgratitude to everyone who has participated

In the coming pages, you will read about what you will find inthe rest of the book Wherever possible I have used real-worldexamples that you can use in your own development I havetried to present the information in such a way that it is useful toboth first-time and experienced programmers

Chapter 3 , Classes and Objects

REALbasic is an object-oriented programming language, andthis chapter delves into object-oriented programming conceptsand how they are implemented in REALbasic

Chapter 4 , Cross-Platform Application

Development

REALbasic gives you the capability to create applications forWindows, Macintosh, and Linux operating systems This chapterprovides you with some basic information about the differencesamong the platforms that will help you to write quality

applications on all of them

Chapter 5 , Designing a Desktop Application

Desktop applications are applications that make use of a

graphical user interface The REALbasic IDE lets you use thedrag-and-drop feature to design your user interface, and thischapter shows you how

Chapter 6 , XML and Advanced Text Processing

XML, regular expressions, and styled text are discussed in thischapter

Chapter 7 , Console Programming and the Shell

You can also create programs in REALbasic that run on thecommand line, without a graphical user interface You can

interact with the Shell programmatically through REALbasic'sShell class, and you can also write your own console

applications that can be run from within the shell on each

platform

Chapter 8 , Databases

You can design a graphical front-end to your database withoutwriting a single line of code This chapter shows you how

Chapter 9 , Networking and Internet

Programming

Read about REALbasic's networking classes and learn how towrite your very own web server

Chapter 10 , Graphics

This chapter delves into REALbasic's Graphics class and showsyou how to manipulate graphics and draw to the screen

Chapter 11 , Scripting and Extending REALbasic

to make your REALbasic application scriptable You'll also begiven an overview on how you can extend REALbasic by usingshared libraries and writing plug-ins in C++

Appendix

Read about where you can go online to find additional

information and how to get copies of the sample code

referenced in the book

REALBASIC IS A MODERN, OBJECT-ORIENTED DESCENDENT ofthe venerable Basic programming language that I first

encountered in my high school computer programming class,whose code I laboriously typed out on a dot-matrix terminal

The original version of the language was developed in 1964 Itwas designed to be a good language for beginning

programmers to learn, which is the very reason I learned to use

it In fact, the name "Basic" means Beginners All-purpose

Symbolic Instruction Code

1970s New life was breathed into the language in 1991, whenMicrosoft released Visual Basic 1.0 (the latest iteration of VisualBasic is known as Visual Basic NET, or Visual Basic 7.0, whichwas first released in 2001) Visual Basic was a modern version

Microsoft released its first version of the language in the mid-of Basic that made it much easier to develop programs withgraphical user interfaces Because it is a highly accessible

it was released in 1998 as a tool for rapid application

development on the Macintosh platform Although AppleScriptwas an easy-to-use language for scripting applications, it wasnot usable at that time as a tool for developing applications As

a result, REALbasic established itself as the perfect entry-levelapplication development environment for the Macintosh

The language has its roots in the Macintosh environment, butthe plan from the beginning was to develop a cross-platform

The next real step forward came in 2003, when REAL Softwareadded a Windows version of the IDE with the release of

REALbasic 5.0 The 5.0 release was an important one for

REALbasic and also included the addition of new features thatmade it a much more viable programming language for seriousapplication developers It included the capability to write

command-line applications and support for XML (which was afeature surprisingly late in arriving) Although you had beenable to compile Windows apps since 1999, this was the firsttime you could develop them in Windows Version 5.5, released

in 2004, added the capability to compile Linux apps

An easier question to answer would be what isn't new in

REALbasic 2005 With the release of this version, the integrateddevelopment environment (IDE) has been totally overhauledand much improved, especially if you have used the Windowsversion of REALbasic 5.5 which, well, let's just let bygones bebygones

With the 2005 release, REAL Software offers integrated

development environments for Macintosh, Windows, and Linux.The IDE was written in REALbasic, which means that the

interface is now consistent across platforms Although you couldcreate cross-platform apps with REALbasic prior to this, the

actual IDE was quite different between the Windows and

Macintosh versions If you are a Windows developer who tried

RB 5.0 and was disappointed with it, you should give RB 2005 achance Your experience will be totally different

The IDE makes it extremely easy to develop applications withgraphical user interfaces (in fact, until RB 5.0, apps with GUIswere all you could create) It provides easy access to databasesand it's possible to write a client app that browses a databasewithout writing a single line of code

There are two versions of REALbasicStandard and Professional.The difference between the two is that with the ProfessionalEdition, you can compile your application in all three platforms,whereas in the Standard Edition, you can compile the

application only for the host environment Although it's officiallycapable of compiling on Linux, I've had success running it onFreeBSD, one of the Unix variants

In my opinion, the single most compelling reason to use

REALbasic instead of something like Visual Basic is that you cancompile REALbasic applications to run natively on Windows,

Macintosh, and Linux machines Whereas older versions of Basicwere interpreted, REALbasic is compiled It also makes use ofthe native operating system whenever possible so that

Macintosh programs act like most other Macintosh programsand most Windows programs act like other Windows programs

There are a lot of languages to choose fromsome closed-sourceand others open-source For example, there is that other cross-platform programming language, Java, for which there are high-quality and free IDEs

The advantage of programming in a modern Basic variant istwofold First, an awful lot of us have programmed in Basic

before, so the learning curve won't be too steep Second, Basic

is called Basic because it's supposed to be, well, basic In otherwords, even if you've never heard of Basic before, Basic is agood choice because it is easy to learn

REALbasic has taken a big leap in maturity in recent years, both

as a cross-platform development solution and as a serious toolfor programmers, so don't let the word "basic" fool you You canwrite very complex programs with it Although the best of

REALbasic is the cross-platform application development

potential, it also lets you pop the hood and get deep into theunderlying system and do whatever you want This book willfocus on the cross-platform aspects of REALbasic, but I will giveyou enough information to get you started in the more single-platform topics If you're a VB developer, you'll be familiar withDeclares; if you code in C++, you'll be interested in hearingabout writing plug-ins for REALbasic

I'm not the type to gush I'm not an ideological platform freak

or a disciple for some clever and deliciously quirky scriptinglanguage somewhere All languages are good in their own way.Some are better than others at particular tasks In a lot of

situations, which language you use doesn't matter at all

Scrimping on allocating space in your brain to learn yet anotherlanguage is a perfectly acceptable reason to avoid learning anew language After all, learning is a good thing, but so is

spending time with your children

scale enterprise applications It if sits on the server, stick withJava If your project needs a responsive cross-platform

REALbasic is not a replacement for Java, especially for large-graphical user interface, REALbasic may be the perfect solution

Although REALbasic is relatively easy to program with, it's alsonot a scripting language It's definitely a programming

language In particular, it's statically typed and compiled Thismeans that there are some quick and dirty scripting tasks thatare better done in Python (or Perl or Ruby)

As for me, I don't like typing, so I am not particularly pleasedwith any extra typing I might have to do I really don't like

brackets of the sort used by JavaScript and Java, although theyare admittedly useful in certain circumstances For this reason,

I prefer Python for scripting and REALbasic for developing clientapplications When developing content management solutions, Iuse Java and Apache Cocoon on the server

If you're learning to program and you need to pick a language

to learn in, I can think of no better language than REALbasic.Java is a lot easier to learn if you already know Basic Python isgood, but it lacks an IDE with the polish of REALbasic;

therefore, it is not as easy to develop GUI applications in

to design a user interface to provide a novice programmer withenough psychological gratification and sense of accomplishment

to give them the energy to overcome the obstacles and

challenges that are such an integral part of the programmingchallenge

document in the front-most window of application such-Experienced REALbasic programmers who want an updatedreference on the new features found in REALbasic 2005

A lot has changed with recent releases You need a

reference to guide you through all the new features and tohelp you negotiate the challenges of cross-platform

development

Visual Basic programmers who want to learn about

REALbasic and how to port applications from Visual Basic toREALbasic

If you fall into this category, you may have an existing

Visual Basic project you want to port to REALbasic so that itcan run on Macintosh and Linux machines You also may belooking for an alternative to Visual Basic 6.0 rather than

"upgrading" to the latest NET Microsoft twiddling

There are even a few Java developers malingering in theshadows of the bookstore who, while deeply loving the

ever-proper, thoroughly stable and dependable Java, stilllong for something a little easier, a little quicker, maybeeven something with a little more gloss on the old user

interface

I'm sure there's even one or two Linux developers who are

frothing at the mouth at the chance to have a commerciallysupported rapid application development tool so that they canquickly create new Linux apps In fact I think REALbasic could

I intend for this book to be helpful to both novice and

experienced programmers alike For the novice, I'll provide

enough background information about programming to get youstarted Although this isn't an introduction-to-programming

book per se, I will certainly keep your interests in mind For theexperienced developer, I will compare and contrast REALbasicwith Java and Visual Basic when it's enlightening to do so, and Iwill highlight any cross-platform "gotchas" you might encounter

Cross-platform application development carries with it someadded complexities that need to be exploredsome features work

in only one of the platforms or work somewhat differently ineach platform It is also likely that many readers will not haveaccess to all three operating systems on their desktop for

thorough cross-platform testing throughout the developmentenvironment As a result, I will provide as much information aspossible about the nuances of cross-platform development withREALbasic and help you avoid lengthy and tedious bug-fixing in

an effort to compile the program on all three platforms

Although REALbasic is flexible enough to let the programmerhave direct access to the underlying operating systems, of

necessity, this is done differently with each respective operatingsystem In many cases, the REALbasic developer will have

relatively deep experience in one platform, but much less

understanding of the others I will provide basic information onhow to use these tools to extend REALbasic, but space and timelimitations mean that I can provide only limited information

about the underlying operating systems and libraries that areavailable to you In other words, this is a book about

programming cross-platform applications in REALbasic It is not

a book about programming Macintosh, Windows, and Linux

operating systems

controls available to programmers Because REALbasic is

extensible with plug-ins, there are several commercially

available plug-ins for REALbasic that add valuable functionality

I will also highlight the most useful of these third-party tools sothat you can evaluate them for your own particular

programming needs

oriented, and event-driven programming language with singleinheritance Whew That just about sums it up If you knowwhat this chapter's first sentence means, then much of thischapter will be a review of familiar concepts If you have noidea what I'm talking about, read on

REALBASIC IS A LINE-ORIENTED, STATICALLY TYPED, object-If you are new to programming in general, or to object-orientedprogramming in particular, you should read this entire chapter

It will introduce you to the basic concepts and terminology youneed to know to make sense of the rest of the book In addition

to those introductory concepts, this section covers REALbasic'sintrinsic data types, built-in functions, and the steps required tocreate your own modules and classes

There's sort of a chicken-and-egg problem when writing aboutprogramming languages, especially REALbasic To get started,you need to learn some basics about the IDE, but to learn thebasics about the IDE, you'll need to understand some

fundamental programming concepts

In an effort to overcome this obstacle, I'll provide a brief

introduction to the IDE in the next section

The computer itself speaks in a language of numbersones andzeros I still find it remarkable all the things that we can do withones and zeros For a computer to work with these ones andzeros, it needs to be able to represent them, so it must have aplace to store and then find these ones and zeros when it needsthem Then the computer can perform a calculation on them Itcan add them together or subtract them or do some

combination and come up with more ones and zeros Ones andzeros are meaningful and they represent meaningful things Insome cases they represent numbers, whereas in other casesthey represent letters and words Basically, we can say thatcomputers can store information and perform calculations on(or process) information

In a procedural programming language, these two distinct

activities are clearly separated Constants and variables storedata and subroutines, and functions perform some kind of

calculation on the data In object-oriented programming, thisdistinction becomes a little more muddy because a class

represents a collection of constants, variables, subroutines, andfunctions Whereas constants can refer only to values (known

as scalar references), variables can be one of two types: a

scalar, which refers to a value, or the variable can be a

reference to an object (An object is an instance of a class; I'llexplain this in more detail soon.)

When we say that REALbasic is an object-oriented language,what do we mean? A programmer may tell you that it meansthat REALbasic isn't a procedural or imperative programminglanguage, and she would be absolutely right Of course, youmight be saying, "So what does that mean?" The differencebetween object-oriented programming and procedural

programming is twofold In part, it's a different way of

organizing the information and instructions that are used to

organizes the instructions and the information into things calledclasses These classes describe the instructions and the

information that go together to get these tasks done

REALbasic takes a practical approach to all of this and it

incorporates procedural-type programming and object-orientedelements In its attitude and the terminology used, it's all

object-oriented

Terminology used to describe programming languages varies bylanguage Although similar concepts exist in all object-orientedlanguages, they don't all share the same set of features andfrom time to time refer to things using different terminology orthe same terminology with a slightly different meaning

REALbasic is no different Before getting started, I want to

provide a quick preview of the terminology I will be discussingthroughout the rest of the chapter

Programming code in REALbasic is organized and presented in ahierarchy When you create an application in REALbasic, youstart with a project All the programming code that you write forthe application is stored in this file A project consists of a

collection of modules and classes

Project

Module

ConstantsPropertiesMethodsSubroutineProgramming codeFunction

ConstantsPropertiesEventsProgramming codeMenu handlers

Programming codeMethods

SubroutineProgramming codeFunction

Programming code

In this list, you can see that a project is made up of modulesand classes Modules and classes represent two differentapproaches to programming: procedural and object-oriented.Although REALbasic is a modern, truly object-oriented

programming language, it retains elements of proceduralprogramming features when it makes sense in order to makethe process of writing an application simpler and more

streamlined

REALbasic uses what is traditionally thought of as object-oriented terminology to describe modules If we were purists,

we would not say that modules have properties or methods.Instead, we would refer to them as global variables or

subroutines and functions Regardless, the folks at REALbasichave opted to use object-oriented terminology for all aspects ofthe language, so that's what I will do as well

Classes and modules are made up of things such as constants,

properties, and methods, and I will refer to them generically

as members A particular method implemented in a class is a

member of that class, as is a property that has been declaredfor that class

I said earlier that programs can either hold data or process

data Data can be held in memory as a constant or a property.Methods are where the data gets processed

All the programming code you write will be written in a method.Methods come in two flavors: functions and subroutines

Functions and subroutines are composed of a series of

statements, which serve as instructions to the program that tell

it the kind of calculations to perform on data

In addition to methods, classes implement events and menuhandlers, which are basically methods with some special

oriented programming

For you to get a sense of how REALbasic works and how

powerful it can be, I want to quickly step you through your firstREALbasic application I am averse to "Hello, World" examples,

so I've come up with a better idea Your first REALbasic

application will be a web browser Don't fret It really is thateasy

When you launch REALbasic, it will launch a new untitled

project by default (see Figure 2.1) In the Project tab of the

main window, you'll see three items listed: App, Window1, and MenuBar1, as shown in Figure 2.1 These are three

classes that are part of every REALbasic application

Figure 2.1 The default "Untitled" project

Window.

[View full size image]

programming What's important to understand now is that aclass represents a group of code that performs a specific task

The Window1 class is the programming code that manages the primary window in the application MenuBar1 handles the

another for editing the code You can switch between modes bypressing Option=Tab, or clicking the Edit Mode button in the

toolbar for Window1 By default we'll be in the Window

Editor's Layout Mode You'll know you're there if the panel is

so that you can actually do something Controls are user-interface elements that users interact with For this project, wewill need three controls All three of them will be found in the

Controls pane in the left column.

The first thing to do is find the PushButton control in the list,

which is in alphabetical order Click it and drag it to the window.Just drop it anywhere for now

You now have a button on your Window with a caption that

reads Untitled To give it a better caption, look in the

Properties pane and find the Caption property in the

Appearance section Click where it says Untitled, and the EditField will become highlighted Type in the word "Go!" or

whatever word you want to use and press Return

Your button should now say "Go!" You'll want the button

positioned in the upper-right corner of the window, so select itand drag it up and to the right Keep dragging it until you seegreen guidelines You should reach a point where there is ahorizontal guide on the top of the button and a vertical guide tothe right of the button These guidelines help you to positionyour controls consistently, according to design guidelines

established by the operating system It's a good idea to usethem and follow their advice

Now that we have a PushButton on the window, we'll need an

EditField Find the EditField in the list of controls and drag it

onto the window just like the button Drag it to the upper-left

will ensure that the EditField is positioned at the same level as the PushButton and that everything looks nice There's no caption to change for the EditField, so we're done with it for

now

Now, find the HTMLViewer control in the list of controls and

drag it to the window Drop it in the center Notice that everytime a control is selected, it is highlighted, and little white

boxes appear in the corners and in the middle of the sides Youcan use these selection boxes to make the control bigger bydragging them around The guides will help you here, too

When it is as big as the guides say it should be, turn to the

Properties pane You will see four CheckBoxes in the

Position section of the Properties pane Check all of them: LockLeft, LockTop, LockRight, and LockBottom This tells

REALbasic that the HTMLViewer should get larger as the

window gets larger Recall that earlier when we were examiningthe window, we made sure that it was expandable and had a

Maximize button.

So far, so good Now for some code

Double-click the PushButton labeled "Go!" and you will be switched to the Code Editor In the left column you'll see the

Code Editor's Browser with a list of all kinds of things You

should see an item called PushButton1, and right beneath it is the word Action, which should be highlighted.

Events

This is the Action event of the PushButton, and we're going

to instruct the PushButton on what it is supposed to do when

someone clicks it REALbasic is an event-driven language Thismeans that much of what your REALbasic program does is inresponse to a user's interaction with your application In this

You have just told the HTMLViewer1 control to execute the

method called LoadURL EditField1.Text is a parameter that you

pass to HTMLViewer1 to let it know which page to load In this case, it takes the content of the EditField1 control and uses

that as the URL (web address) of the page to load

Whereas HTMLViewer1.LoadURL refers to a method, EditField1.text

refers to something else, called a property EditField1 is an instance of the class EditField, and EditField1.text is a property

of the class instance Later on in this chapter I'll cover methodsand properties in more detail, but for now let it suffice to saythat a method is an instruction to a computer to perform sometask, and a property represents a value of some sort In thiscase, EditField1.Text represents the value of the text that the

Voila! You've created a web browser

If it doesn't work as planned, that's okay Take a look and makesure that you have typed everything exactly the way I said totype it in If the program is generating an error, a small windowwill pop up describing the error Possible errors might include

clicking the "Go!" button when the EditField contains no text,

or your program may generate an error if you try to run it andyou are not connected to the Internet

Now that you've had a taste of how easy it is to write a

REALbasic program, it's time to look at some of the details ofthe REALbasic programming language and how to create classesand modules of your own