TweetFollow Us on Twitter

Sprocket Linked List 2
Volume Number:11
Issue Number:3
Column Tag:Getting Started

Adding Your Own Class to Sprocket, Part 2

Where to hook in with a linked list class...

By Dave Mark, MacTech Magazine Regular Contributing Author

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

Last month we created and tested a pair of classes that implemented a doubly linked list. This month we’ll look at the process of adding the linked list classes to a Sprocket project. Our goal is to create a linked list when the application starts up, then add a link to the list every time a new document is created. Each link in the list would contain a pointer to a TDocument object. When a document is closed, its corresponding link is removed from the list. When the application shuts down, the list is deleted.

Pre-Flighting Sprocket

Before you add new code to Sprocket, your first job is to make sure you have the latest version of Sprocket, and that you can get it to compile. As you no doubt have discovered for yourself, Macintosh development environments have an unsettling habit of changing with each new release, breaking your code in the process. The biggest reason for this is that Apple continuously updates their interface files, sending a constant stream of updates to the various compiler vendors. As of this writing, the latest version of Sprocket was built to run with a pre-release version of Code Warrior version CW5, which includes a slew of new headers. Though you can get the new version of Sprocket to compile using older versions of CodeWarrior, it will take a fair amount of work. Unfortunately, it would be impossible to continue to update Sprocket and to maintain compatibility with older versions of the various development environments. If you have any ideas about how we should be handling this problem, please send them along to our illustrious editor Scott (you can reach him at editorial@xplain.com).

As we go to press, Symantec had not yet released a version of Symantec C++ with the new Universal Headers, though by the time you read this, they likely will have. Since I can’t compile Sprocket using Symantec C++, all the figures in this month’s column are based on CodeWarrior. Hopefully, Symantec will make the new headers available in time for next month’s column.

When you go to any of the standard MacTech sites to download Sprocket
(see p. 2), there are two archives you’ll need. One should be called something like “Sprocket.12-15-94.sit” and the other something like “SprocketSample.12-15-94.sit”. The date in the middle is the date the archive was created, and should be about three months earlier than the date this article appears. The Sprocket archive contains the files that make up the Sprocket framework. The SprocketSample archive contains a few additional source code files, as well as a project file that brings the Sprocket and SprocketSample source together. The idea here is that Dave Falkenburg maintains Sprocket, while I maintain SprocketSample. Sprocket is a framework, while SprocketSample is an application that brings the framework to life. [You’ll be able to find the 12-15-94 versions, as well as any more recent releases at the online sites - ed stb]

Create a Sprocket folder on your hard drive, download and decompress the two archives, and copy each of the new folders into the Sprocket folder. Be sure each of the two folders has a date. This will distinguish the current Sprocket and SprocketSample folders from the versions you’ll download in following months. Figure 1 shows my master Sprocket folder. It contains one subfolder with the current version of Sprocket and another with two different versions of SprocketSample. The “before” folder contains all the SprocketSample code before I added in the list classes. The “after” folder contains the same program, this time with the list classes integrated in. We’ll start by getting the “before” version of SprocketSample to compile. Next, we’ll go through the process of converting the “before” version to the “after” version, then compile and run the “after” version.

Figure 1. My master Sprocket folder,
showing the folders for Sprocket and for SprocketSample.

Compiling the “Before” Version of SprocketSample

Each SprocketSample project is divided into two parts. The first part (the upper half of the project window) contains references to SprocketSample source code, while the second part (the lower half of the project window) contains references to Sprocket source code (Figure 2).

Figure 2. The 68K CodeWarrior version of the SprocketSample project.

To get the code in your SprocketSample project to compile, you’ve got to make sure the compiler can find all of the project’s files. If you are using CodeWarrior, launch either the PowerPC or 68K project, select Preferences... from the Edit menu, then scroll down to and click on the Access Paths icon (Figure 3). The rectangle labeled User: shows the paths that will be searched for source code files. The rectangle labeled System: shows the paths that will be searched for things like system include files. You want to make sure that the User: rectangle contains one additional path besides that leading to the project folder. The additional path is the folder containing the Sprocket source code. If this second path is there, but is wrong, click on it and press the Change button, then navigate into and select the folder containing the Sprocket source code. If the second path is there and looks good, just leave it alone. If there is no second path, click on the Add button and select the folder containing the Sprocket source code.

Figure 3. The CodeWarrior Access Paths preferences panel.

The point is, you want to make sure the compiler can find the Sprocket source code as well as the SprocketSample source. You know that the compiler will find the SprocketSample source code since it is in a subfolder inside the project folder. Once your new folder appears in the User: rectangle, click the OK button to save your preferences.

Next, you’ll need to make sure that your CodeWarrior project includes the proper precompiled header file. If you look at the project window shown in Figure 2, the very first file in the project is named SprocketSampleHeaders68K.pch++. This file is a source code file which will be precompiled, then used to compile all the other source files in the project. By precompiling all the #includes and #defines used by all your source code files, you can significantly reduce your compile times.

When CodeWarrior encounters a project file that ends in “.pch++”, it compiles the file into a precompiled header, saving the header in the same folder as its corresponding “.pch++” file. Select Preferences... from the Edit menu, then scroll down to the Language preferences. The Prefix File field tells the compiler which precompiled header to use when it compiles the project source code files (Figure 4). Make sure that the field contains either SprocketSampleHeaders68K or SprocketSampleHeadersPPC, making sure it matches the “.pch++” file in your project.

Figure 4. CodeWarrior’s Language preferences panel.

If you are using Symantec C++, you’ll have to address these same issues and get hold of the latest Universal Headers. That’s about it. You are now ready to take the “before” version of SprocketSample for a spin. Once you get everything to compile, you’ll see the familiar splash screen, menu bar, and empty tool palette window. Once you’ve had a chance to play with SprocketSample for a bit, quit and let’s add our list classes into the mix.

Adding the List Classes

Just as a reminder, here are the two linked list class definitions. TLinkedList is the linked list itself and TLink is a single link:

class    TLinkedList
{
  public:
                            TLinkedList();
    virtual                 ~TLinkedList();

    virtual    OSErr        CreateAndAddLink( void *objectPtr );
    virtual    OSErr        FindAndDeleteLink( void *objectPtr );
    virtual unsigned long   CountLinks();
    virtual void            *GetNthLinkObject( unsigned long 
                                                 linkIndex );

  protected:
    virtual void            DeleteAllLinks();
    TLink                   *FindLink( void *objectPtr );
    virtual OSErr           DeleteLink( TLink *linkPtr );
    
    TLink                   *fFirstLinkPtr;
    TLink                   *fLastLinkPtr;
};

class    TLink
{
  public:
                    TLink( void *objectPtr );
    virtual         ~TLink();
    virtual void    SetPrevLink( TLink *prevLinkPtr )
                        { fPrevLinkPtr = prevLinkPtr; }
    virtual void    SetNextLink( TLink *nextLinkPtr )
                        { fNextLinkPtr = nextLinkPtr; }
    virtual TLink   *GetPrevLink()
                        { return fPrevLinkPtr; }
    virtual TLink   *GetNextLink()
                        { return fNextLinkPtr; }
    virtual void    *GetObjectPtr()
                        { return fObjectPtr; }

  protected:
      TLink         *fPrevLinkPtr;
      TLink         *fNextLinkPtr;
      void          *fObjectPtr;
};

The first thing you’ll need to do is copy the four source code files that make up the TLinkedList and TLink classes into the same folder as the SprocketSample source code. In this case, you’ll copy the files LinkedList.cp, LinkedList.h, Link.cp, and Link.h into the SprocketSample folder located inside the folder named SprocketSample, Before. Be sure to add Link.cp and LinkedList.cp to the first half of the project window.

Next, you’ll need to modify SetUpApplication() to create a new TLinkedList object and QuitApplication() to step through the list and close all the documents stored in the list. You’ll also need to create a global variable containing a pointer to the TLinkedList object. To do that, create a file called SprocketSample.h and type in the following code:

#include "LinkedList.h"

extern  TLinkedList*gListPtr;

Save SprocketSample.h in the same folder as all the other SprocketSample source code.

Next, open the file SprocketSample.cp and add these two lines at the top:

#include "SprocketSample.h"

TLinkedList *gListPtr;

Now scroll down to the first routine in SprocketSample.cp, which should be SetupApplication(). Here’s where you’ll create a new TLinkedList object. Add this line at the beginning of SetupApplication():

gListPtr = new TLinkedList;

Scroll down about 4/5 of the way down in SprocketSample.cp and find the routine QuitApplication(). Change the routine so it reads like this:

Boolean QuitApplication(void)
{
 unsigned long numLinks, counter;
 TDocWindow *myDocPtr;
 OSErr  err;
 
 numLinks = gListPtr->CountLinks();
 for ( counter=1; counter<=numLinks; counter++ )
 {
 myDocPtr = (TDocWindow *)gListPtr->GetNthLinkObject( 1 );
// If the user cancels the close, return false to cancel the quit...
 if ( ! myDocPtr->Close() )
 return false;
 else
 delete myDocPtr;
 }
 
 return true;
}

The main purpose of QuitApplication() is to step through the list of documents, sending each document object a close message. If a document has changed since it was last saved, its close method will give the user a chance to cancel the close. If the close is canceled, we’ll exit the loop by returning false, thus canceling the quit. If the user doesn’t cancel a close, the TDocWindow object under consideration is deleted.

A few things worth noting here. Notice that we delete the TDocWindow but don’t remove it from the list first. That is done in the TDocWindow destructor. Deleting it from the list inside the TDocWindow destructor has two advantages. First, this keeps us from having to remember to delete the TLink every time we delete a TDocWindow. Secondly, this ties the deletion of the link as closely as possible to the actual deletion of the TDocWindow, keeping us from the nasty situation where we have a TDocWindow that isn’t in the list or where we have a TLink that points to a TDocWindow that’s already been deleted.

Take some time to look through the code that closes documents. Look in SprocketMain.cp at the code that handles clicks in a window’s close box and at the code that handles the Close and Quit menu items. Also check out the code that responds to the quit application Apple event. This code will probably change slightly in the future, but it won’t change by much. The most likely change is to merge all the above-mentioned code so that it all closes documents the exact same way.

Our final task is to modify the TDocWindow constructor and destructor. The constructor needs to embed a pointer to the new TDocWindow in a TLink, adding the TLink to the list pointed to by gListPtr. The destructor needs to find the TLink containing the TDocWindow about to be destroyed, and remove that link from the list.

Before you edit the constructor and destructor, you’ll need to add this line to the beginning of DocWindow.cp:

#include "SprocketSample.h"

This will give you access to the global gListPtr as well as to the TLinkedList class.

Now add these three lines to the end of the TDocWindow() constructor:

 err = gListPtr->CreateAndAddLink( this );
 if ( err != noErr )
 DebugStr((StringPtr) "\pAdd Doc to list failed");

The first line adds a pointer to the current object to the list, while the second two lines drop us into MacsBug if the add failed.

Add these three lines to the ~TDocWindow() destructor:

 err = gListPtr->FindAndDeleteLink( this );
 if (err != noErr)
 DebugStr((StringPtr) "\Delete doc from list failed");

The first line deletes the TDocWindow from the global linked list. The second two lines drop us into MacsBug if the delete fails.

Running the New, Improved SprocketSample

OK, now that all your changes are in, run your new version of SprocketSample (or, if you just can’t wait long enough to type in the changes, run the version of SprocketSample in the SprocketSample, After folder). Select New from the File menu and create 3 new documents. Next, click in the close box of the frontmost window. You’ll be prompted to save the changes in that window. Click the Save button.

Now select Quit from the File menu. Once again, you’ll be prompted to save changes in a document, but this time you’ll be prompted to save the changes in the first document in the global TLinkedList, which should be the document named “Untitled-1”. If you click the cancel button, the quit should be aborted and you should be left running as you were before you selected Quit.

Experiment with various cancel and saving combinations. Try sending a quit application Apple event to SprocketSample by launching this script from the Script Editor:

tell application "SprocketSample.68K"
 quit
end tell

Be sure to change the name of the application in the tell clause if you are not running with the 68K version of CodeWarrior. Use the debugger to follow the code. Though Sprocket might seem a little intimidating, it’s really not that hard to follow once you get into it, especially if you confine yourself to a specific functional area or thread.

Until Next Month

In next month’s column, we’ll look into Sprocket’s menu handling model and add our own menus to Sprocket’s menu bar. The current plan is to replace the existing menu-processing code with a new design that more closely approximates that used by OpenDoc. The idea is, if you learn how to handle menus in Sprocket, you’ll have a leg up when you start writing your first OpenDoc part.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Minecraft 795 - Popular sandbox building...
Minecraft allows players to build constructions out of textured cubes in a 3D procedurally generated world. Other activities in the game include exploration, gathering resources, crafting, and combat... Read more
djay Pro 3.0.5 - Transform your Mac into...
djay Pro provides a complete toolkit for performing DJs. Its unique modern interface is built around a sophisticated integration with iTunes and Spotify, giving you instant access to millions of... Read more
Unicorn HTTPS 1.5.54 - Change DNS quickl...
Unicorn HTTPS can change DNS quickly and easily. Every function is served free of charge, no advertisement. Your personal information is never collected by us. Please use it with confidence. Faster... Read more
MarsEdit 4.4.11 - Quick and convenient b...
MarsEdit is a blog editor for OS X that makes editing your blog like writing email, with spell-checking, drafts, multiple windows, and even AppleScript support. It works with with most blog services... Read more
Printopia 3.0.16 - Share Mac printers wi...
Run Printopia on your Mac to share its printers to any capable iPhone, iPad, or iPod Touch. Printopia will also add virtual printers, allowing you to save print-outs to your Mac and send to apps.... Read more
beaTunes 5.2.19 - Organize your music co...
beaTunes is a full-featured music player and organizational tool for music collections. How well organized is your music library? Are your artists always spelled the same way? Any R.E.M. vs REM?... Read more
Navicat Premium Essentials 15.0.25 - Pro...
Navicat Premium Essentials is a compact version of Navicat which provides basic and necessary features you will need to perform simple administration on a database. It supports the latest features... Read more
Apple Pages 10.3.9 - Apple's word p...
Apple Pages is a powerful word processor that gives you everything you need to create documents that look beautiful. And read beautifully. It lets you work seamlessly between Mac and iOS devices, and... Read more
Numbers 10.3.9 - Apple's spreadshee...
With Apple Numbers, sophisticated spreadsheets are just the start. The whole sheet is your canvas. Just add dramatic interactive charts, tables, and images that paint a revealing picture of your data... Read more
Suitcase Fusion 21.2.2 - Font management...
Suitcase Fusion is the creative professional's font manager. Every professional font manager should deliver the basics: spectacular previews, powerful search tools, and efficient font organization.... Read more

Latest Forum Discussions

See All

Honkai Impact 3rd has revealed more deta...
Honkai Impact 3rd has now announced more details about its upcoming crossover with Neon Genesis Evangelion. This is set to arrive next week on January 22nd and will introduce an exclusive story, battlesuit and weapon to the popular action-RPG. [... | Read more »
Space Frog Intern, James Bolton's a...
James Bolton's arcade shooter Space Frog Intern is now available for Android devices following its release on iOS last year. It sees players taking control of the titular amphibian and blasting their way through various space beasties. [Read more... | Read more »
The 5 Best Mobile Ports
Ports or coversions of games from one platform to another can be quite tricky. This is especially true when porting games to phones and tablets, as these titles have to be designed with workable touch controls and account for smaller screen sizes... | Read more »
Erica, the PS4-exclusive FMV thriller, c...
London-based studio Flavourworks is bringing its FMV game Erica to iOS on Friday as a free trial, with a full release presumably following later. This is the second platform the game has launched on after its original release on PlayStation 4 two... | Read more »
Cute simulation game Dinosaur Park: Prim...
Dinosaur Park: Primeval Zoo is a cute zoo simulation game from upjers, and it sounds perfect for anyone who’s a dinosaur fan. It’s coming to Android in February, and is available right now for pre-registration. [Read more] | Read more »
Genshin Impact - Lost Riches Guide
| Read more »
Figment: Journey into the Mind, the surr...
Following its release on iOS devices last year, Bedtime Digital Games' surreal action-puzzler Figment: Journey into the mind will be heading for Android next Thursday, January 14th. If you're unfamiliar, it follows Dusty and his pal Piper as they... | Read more »
Skylanders Ring of Heroes' latest u...
Following the various game-changing updates made to Skylanders Ring of Heroes last year, the latest update to Activision and Com2uS' team-based RPG has introduced a new battle mode and they will celebrate its arrival with various in-game events... | Read more »
Distract Yourself With These Great Mobil...
There’s a lot going on right now, and I don’t really feel like trying to write some kind of pithy intro for it. All I’ll say is lots of people have been coming together and helping each other in small ways, and I’m choosing to focus on that as I... | Read more »
Genshin Impact - Combat Tips
Genshin Impact isn't a terribly difficult game, but its enemies get tougher the longer you play it and as your world level increases. This makes sense as a progression system, but it can also create gnarly difficulty spikes that are hard to... | Read more »

Price Scanner via MacPrices.net

At only $809, these are the cheapest MacBooks...
Apple has restocked at full line of Certified Refurbished 2020 13″ Intel-based MacBook Airs available starting at only $809 and up to $280 off original MSRP. Each MacBook features a new outer case,... Read more
Find the best price on an Apple iPhone MagSaf...
Looking for an Apple MagSafe Charger for your new iPhone 12, or perhaps an Apple MagSafe Duo Charger for your new iPhone and Apple Watch? Check out our new MagSafe Charger Price Tracker. We scan the... Read more
Save $67 on 13″ M1 MacBook Pros at Expercom,...
Apple reseller Expercom has 2020 13″ M1 MacBook Pros on sale for $67 off Apple’s MSRP with prices starting at $1232. In addition to their MacBook Pro sale prices, take $40 off AppleCare+ when... Read more
Back in stock! 16″ MacBook Pros starting at o...
After a long absence, Apple has restocked a full line of Certified Refurbished 16″ MacBook Pros for up to $420 off the cost of new models, starting at $2039. Each model features a new outer case,... Read more
Saturday Steal! Clearance 2020 Mac mini for o...
Other World Computing has clearance 2020 Intel-based 4-core Mac minis on sale for only $549 this weekend, $250 off Apple’s original MSRP. These are new, unopened, factory-sealed models: – 3.6GHz 4-... Read more
Save up to $112 on 13″ Intel-based MacBook Pr...
Apple reseller Expercom has 2020 13″ 2.0GHz Intel-based MacBook Pros on sale for $100-$112 off Apple’s MSRP with prices starting at $1699. In addition to their MacBook Pro sale prices, take $70 off... Read more
New sale at B&H: Apple’s hot new 13″ M1 M...
Apple’s new 2020 13″ MacBook Pros with M1 Apple Silicon CPUs are on sale at B&H Photo today for $50-$100 off MSRP, starting at $1239. Free expedited shipping is available for most addresses in... Read more
New at US Cellular: Your choice of free iPhon...
US Cellular has the 64GB Apple iPhone 12, 64GB iPhone 12 mini, and 64GB iPhone SE each available for free for new customers signing up for an Unlimited data plan. Cost of the phone is spread over a... Read more
Verizon offers $30 discount on Apple AirPods...
Verizon has Apple AirPods Pro on sale for $219.99 on their online store through January 22, 2021. Their price is $30 off Apple’s MSRP, and it’s among the lowest prices currently available for AirPods... Read more
Apple has clearance 2020 13″ 1.4GHz Intel-bas...
Apple has clearance, Certified Refurbished, 2020 13″ 1.4GHz 4-Core Intel-based MacBook Pros available starting at $1059 and up to $270 off original MSRP. These are the cheapest MacBook Pros for sale... Read more

Jobs Board

*Apple* Administrator - Freedom Mortgage (Un...
Apple Administrator + Job ID:8595 + Functional Area:Information Technology + Employment Type:Full Time + Location:Moorestown, NJ + Department:IT Conferencing & AV + Read more
Systems Architect, *Apple* Production Engin...
…package beginning on your first day? If so, we hope you'll keep reading! The Apple Sales Engineering and account team is looking for a stellar presales engineer with Read more
*Apple* /Mac Support Engineer - BRMi (United...
**Overview** BRMi Technology is currently seeking an Apple /Mac Support Engineer for a large client. The support engineer will research, evaluate, design, implement, Read more
Security Officer - Temporary - *Apple* Stor...
**Security Officer \- Temporary \- Apple Store** **Description** Summary The Security Officer provides services for a variety of large and small business clients Read more
Transition Into Practice (TIP) - April 2021-R...
…Academy-Transition into Practice (TIP) Residency program at **St Mary Medical Center in Apple Valley, CA.** **We are seeking Registered Nurses who are:** + New Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.