TweetFollow Us on Twitter

Apr 96 Top 10
Volume Number:12
Issue Number:4
Column Tag:Symantec Top 10

Symantec Top 10

By Andy McFarland, Symantec Technical Support

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

Q: I have written a constructor for my CPanorama derived class so I can pass some specific initial values, but now all the parts of the object I specified in the Visual Architect are coming up NULL or garbage. What’s going on?

A: When it comes time to instantiate a class created in Visual Architect, a TCL macro new_by_name is used. It calls a (default) constructor if you have written one, or simply an implied (default-default) constructor if you have not. In either case, the information you specified in the VA is read in from the resource file with GetFrom() after all the constructors in the inheritance chain for your class have been called.

VA can call only default constructors. This includes constructors with no parameters and those for which all the parameters have default values. If you write a constructor that requires that at least one value be passed, you will be creating an object separate from the one VA is going to create. You may still initialize non-TCL members which may have been added to your VA-generated class either in the body of a default constructor or as parameters with default values.

Override GetFrom() if you need to use information from the VA resource file in your intitialization. For instance, a Rect frameRect might be used to save you from having to use the LongToQDRect() macro in toolbox calls that require a Rect. It is perfectly valid (and may be simpler) to put all of your construction/initialization code into GetFrom(), and not write a constructor at all.

Q: VA conveniently creates Save and SaveAs file menu items. What do I actually have to do to save my document to a file?

A: CDocument has a data member itsFile, a CFile*, which will point to whatever species of CFile you actually create, such as CDatafile, CResFile or CPictFile, etc.

The Save As menu item is connected to CDocument:: DoSaveFileAs(). PickFileName() is called from there, which puts up a StandardPutFile() dialog to retrieve the vitals of the file-to-be in an SFReply record.

Finally, DoSaveFileAs() passes the SFReply record to DoSaveAs(), which is what you need to overide in your document class, i.e. in CMain. At this point you need to allocate space for itsFile if you haven’t already.

Now just use all the nifty methods inherited from CFile, CDataFile and perhaps CPictFile to do things like creating, opening, closing, reading and writing to the file and changing its name. For simple file I/O, you may never have to call a File Manager routine directly.

Q: I’m trying to use the TCL macro new_by_name() with a VA-generated class, but it’s not working. What’s up?

A: At the beginning of the file you will see TCL_DEFINE_CLASS_M1(Cfoo,x_Cbar). This is the macro that makes the class an RTTI class (type “Run-Time Type Identification” into THINK Reference for a full explanation.) VA defaults to the M1 suffix, which must be changed to D1 if new_by_name() is to be used. Note that most people will rarely, if ever, need to use new_by_name() instead of TCL_NEW().

Q: Is it possible to create and use a routine descriptor for a member function? When I do so, the arguments are assigned in the wrong order.

A: No. There are various problems involved. There are some implied parameters to member functions, like the this pointer (a pointer to the object). Further, the parameters are passed in a different order (Pascal style) but stack cleanup is done C-style.

Q: I’m getting error -1708, “Couldn’t complete the last command because the AppleEvent was not handled”, when trying to build a library.

A: This usually results from the ToolServer not being installed properly. Check to be sure there is an alias for ToolServer in the (Tools) folder. Also, be sure to rename the alias as “ToolServer”. You may also need to copy the Toolserver folder from the CD, Apple Software:Tools: Toolserver1.1.1, to your hard drive.

Q: How do I get the Standard Console to accept single keystrokes without a Carriage Return?

A: Use the csetmode() function.


#include <stdlib.h> // For Constant EXIT_SUCCESS

#include <iostream.h> // For C++ I/O, cin and cout

//#include <stdio.h> // If you use straight C I/O

#include <console.h> // For cgetmode

main()

{

char c;

printf( "Type a character: ");

csetmode(C_CBREAK,stdin); // Allow single key inputs

c = getchar();

printf( "\nYou typed: '%c'", c, "\n" );

return 0;

}


Q: When I bring my SPM project up to date, a Build Errors window shows up but is empty. What’s going on?

A: Your code is probably generating compiler warnings that you aren’t seeing because the Build Errors window is set to hide them. Click on the Show Warnings button.

Q: Can I use exception handling without the TCL?

A: To use exception handling without the Think Class Library, you must include BRLib and Exceptions.cp in your project. Also, you must compile with the directive:


#define NO_TCL


The four macros used to make exception handling work correctly are:


AUTO_DESTRUCT_OBJECT

TCL_NEW

TCL_END_CONSTRUCTOR

TCL_START_DESTRUCTOR


The macro AUTO_DESTRUCT_OBJECT will guarantee that the destructor is called for an automatic object on the stack. A destructor will work only on a completely constructed object. TCL_END_CONSTRUCTOR helps the compiler to determine the complete construction of an object.

See the example below to see how the macros are used.


class funClass TCL_AUTO_DESTRUCT_OBJECT //macro in class header

{

public:

funClass() { // no arg constructor

cout << "In constructor." << endl;

char * myStr = new char[64]; // allocate memory

TCL_END_CONSTRUCTOR // End of the constructor

}

virtual ~funClass() { // virtual destructor

TCL_START_DESTRUCTOR // Beginning of the destructor

cout << "In destructor." < <endl;

delete [] myStr; // deallocate memory

}

};


Q: Okay. I’ve done everything I’m supposed to do to use exception handling without the TCL, but I get a bunch of link errors when I try to use TCL_NEW.

A: Rebuild BR_Lib.o with

 
  #define TCL_UNSAFE_ALLOCATION.

Q: Why does writing a text handle using CSaver cause garbage in the stream when I read it in?

A: When you create an arbitrary length handle and then fill only part of it, the whole handle length is written (and then read) and so you end up with garbage. To get CSaver to work correctly with handles, you need either to create a handle the right size to begin with, or to resize it when assigning the text to it. As an example we will stream out a CEditText object.

Within the myContents.cp file:

    

// Don’t bother allocating space for the handle.


In GetFrom(), stream in the text:


stream >> myMainText;


In PutTo(), stream out the handle and kill it:


stream << myMainText;

DisposHandle(myMainText);


In CMain.cp::WindowToContents, construct the handle, and fill it:


long len = fMain_Pano3->GetLength(); // get the length we want

itsContents->myMainText = NewHandleCanFail( len );

BlockMove( *fMain_Pano3->GetTextHandle(),

itsContents->myMainText, len );


Special thanks to Michael Hopkins, Craig Conner, Glenn Austin, Scott Morison, and Mark Baldwin.

 
AAPL
$96.13
Apple Inc.
+0.53
MSFT
$42.86
Microsoft Corpora
-0.30
GOOG
$566.07
Google Inc.
-5.53

MacTech Search:
Community Search:

Software Updates via MacUpdate

Data Rescue 3.2.4 - Recover lost data on...
Data Rescue is a robust and reliable hard-drive recovery solution for your Mac. Recover lost or deleted files, mount corrupted drives, and more -- Data Rescue offers complete relief from crippling... Read more
Adobe Lightroom 5.6 - Import, develop, a...
Adobe Lightroom software helps you bring out the best in your photographs, whether you're perfecting one image, searching for ten, processing hundreds, or organizing thousands. Create incredible... Read more
OneNote 15.2 - Free digital notebook fro...
OneNote is your very own digital notebook. With OneNote, you can capture that flash of genius, that moment of inspiration, or that list of errands that’s too important to forget. Whether you’re at... Read more
iStat Menus 4.22 - Monitor your system r...
iStat Menus lets you monitor your system right from the menubar. Included are 8 menu extras that let you monitor every aspect of your system. Some features: CPU -- Monitor cpu usage. 7 display... Read more
Ember 1.8 - Versatile digital scrapbook....
Ember (formerly LittleSnapper) is your digital scrapbook of things that inspire you: websites, photos, apps or other things. Just drag in images that you want to keep, organize them into relevant... Read more
OmniPlan 2.3.6 - Robust project manageme...
With OmniPlan, you can create logical, manageable project plans with Gantt charts, schedules, summaries, milestones, and critical paths. Break down the tasks needed to make your project a success,... Read more
Command-C 1.1.1 - Clipboard sharing tool...
Command-C is a revolutionary app which makes easy to share your clipboard between iOS and OS X using your local WiFi network, even if the app is not currently opened. Copy anything (text, pictures,... Read more
Knock 1.1.7 - Unlock your Mac by knockin...
Knock is a faster, safer way to sign in. You keep your iPhone with you all the time. Now you can use it as a password. You never have to open the app -- just knock on your phone twice, even when it's... Read more
Mellel 3.3.6 - Powerful word processor w...
Mellel is the leading word processor for OS X and has been widely considered the industry standard since its inception. Mellel focuses on writers and scholars for technical writing and multilingual... Read more
LibreOffice 4.3.0.4 - Free Open Source o...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more

Latest Forum Discussions

See All

Bio Inc. is $0.99 for the Weekend, Recei...
Bio Inc. is $0.99 for the Weekend, Receives Small Update Posted by Ellis Spice on August 1st, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Happy 7th Birthday Readdle! Thank You fo...
Happy 7th Birthday Readdle! | Read more »
Sharknado: The Video Game Review
Sharknado: The Video Game Review By Lee Hamlet on August 1st, 2014 Our Rating: :: SHARKNA-DON'TUniversal App - Designed for iPhone and iPad Sharknado: The Video Game brings the craziness of the movies to iOS, though it quickly... | Read more »
Clima (Weather)
Clima 1.0 Device: iOS iPhone Category: Weather Price: $.99, Version: 1.0 (iTunes) Description: Clima show you all weather information, just beautifully simple. A series of color bars can tell you at a glance exactly current... | Read more »
Sticky Soccer Review
Sticky Soccer Review By Andrew Fisher on August 1st, 2014 Our Rating: :: STICK THIS GAMEUniversal App - Designed for iPhone and iPad Sticky Soccer puts too much emphasis on the ‘sticky’ and not enough on the ‘Soccer’ or ‘Fun’.   | Read more »
Graphics-less Apocalyptic Adventure A Da...
Graphics-less Apocalyptic Adventure A Dark Room Goes Free for a Limited Time Posted by Rob Rich on August 1st, 2014 [ permalink ] | Read more »
Fraud Tycoon Review
Fraud Tycoon Review By Rob Thomas on August 1st, 2014 Our Rating: :: UNHEALTHY CREDITUniversal App - Designed for iPhone and iPad Fraud Tycoon is a half-baked, messy, promotional tie-in that does their sponsor no favors whatsoever... | Read more »
Guardians of the Galaxy: The Universal W...
Guardians of the Galaxy: The Universal Weapon is on Sale for the Weekend Posted by Rob Rich on August 1st, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Mister Beam Review
Mister Beam Review By Jordan Minor on August 1st, 2014 Our Rating: :: ILLUMINATINGUniversal App - Designed for iPhone and iPad Mister Beam’s puzzles are great. But its platforming? Not so much.   | Read more »
Hook Some More Fun With MapHook’s New Up...
Hook Some More Fun With MapHook’s New Update Posted by Jessica Fisher on August 1st, 2014 [ permalink ] iPhone App - Designed for the iPhone, compatible with the iPad | Read more »

Price Scanner via MacPrices.net

13-inch MacBook Airs on sale for $100 off MSR...
B&H Photo has the new 2014 13″ MacBook Airs on sale $100 off MSRP. Shipping is free, and B&H charges NY sales tax only. They also include free copies of Parallels Desktop and LoJack for... Read more
16GB iPad Air on sale for $399, save $100
Best Buy is offering the 16GB WiFi iPad Air for $399.99 on their online store for a limited time. Their price is $100 off MSRP. Choose free shipping or free store pickup (if available). Price is for... Read more
All Over For Tablets Or Just A Maturing, Evol...
CNN’s David Goldman weighs in on tablet sector doom and gloom, asking rhetorically: “Is this the beginning of the end for the tablet?” Answering that, he contends that hysteria and panic are... Read more
Letterspace 1.0.1 – New Free iOS Text Editor...
Bangkok, Thailand based independent developer Sittipon Simasanti has released Letterspace, a new text editor for iPhone, iPad, and iPod touch devices. Letterspace is a note taking app with an... Read more
Save up to $130 on an iPad mini with Apple re...
The Apple Store has Certified Refurbished 2nd generation iPad minis with Retina Displays available for up to $130 off the cost of new models, starting at $339. Apple’s one-year warranty is included... Read more
iPad Cannibalization Threat “Overblown”
Seeking Alpha’s Kevin Greenhalgh observes that while many commentators think Apple’s forthcoming 5.5-inch panel iPhone 6 will cannibalize iPad sales, in his estimation, these concerns are being... Read more
Primate Labs Releases July 2014 MacBook Pro P...
Primate Labs’ John Poole has posted Geekbench 3 results for most of the new MacBook Pro models that Apple released on Tuesday. Poole observes that overall performance improvements for the new MacBook... Read more
Apple Re-Releases Bugfixed MacBook Air EFI Fi...
Apple has posted a bugfixed version EFI Firmware Update 2.9 a for MacBook Air (Mid 2011) models. The update addresses an issue where systems may take longer to wake from sleep than expected, and... Read more
Save $50 on the 2.5GHz Mac mini, plus free sh...
B&H Photo has the 2.5GHz Mac mini on sale for $549.99 including free shipping. That’s $50 off MSRP, and B&H will also include a free copy of Parallels Desktop software. NY sales tax only. Read more
Save up to $140 on an iPad Air with Apple ref...
Apple is offering Certified Refurbished iPad Airs for up to $140 off MSRP. Apple’s one-year warranty is included with each model, and shipping is free. Stock tends to come and go with some of these... Read more

Jobs Board

Position Opening at *Apple* - Apple (United...
**Job Summary** The Apple Store is a retail environment like no other - uniquely focused on delivering amazing customer experiences. As an Expert, you introduce people Read more
Position Opening at *Apple* - Apple (United...
**Job Summary** At the Apple Store, you connect business professionals and entrepreneurs with the tools they need in order to put Apple solutions to work in their Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Sr. Product Leader, *Apple* Store Apps - Ap...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
Sr Software Lead Engineer, *Apple* Online S...
Sr Software Lead Engineer, Apple Online Store Publishing Systems Keywords: Company: Apple Job Code: E3PCAK8MgYYkw Location (City or ZIP): Santa Clara Status: Full Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.