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2010-05-19
, 08:08
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Posts: 3,319 |
Thanked: 5,610 times |
Joined on Aug 2008
@ Finland
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#12
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Qt also provides some convenience classes for people wishing more pointer automatism:
http://doc.qt.nokia.com/4.6/qscopedpointer.html
http://doc.qt.nokia.com/4.6/qsharedpointer.html
Not exactly garbage collection, but it's as close as it gets to it in 'standard' C++.
http://doc.qt.nokia.com/4.6/qscopedpointer.html
http://doc.qt.nokia.com/4.6/qsharedpointer.html
Not exactly garbage collection, but it's as close as it gets to it in 'standard' C++.
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Blogging about mobile linux - The Penguin Moves!
Maintainer of PyQt (see introduction and docs), AppWatch, QuickBrownFox, etc
Blogging about mobile linux - The Penguin Moves!
Maintainer of PyQt (see introduction and docs), AppWatch, QuickBrownFox, etc
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2010-05-19
, 08:38
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Posts: 124 |
Thanked: 10 times |
Joined on Jan 2007
@ Italy
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#13
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Originally Posted by gri
so in constructor method i've to define:
Parent can be any class that inherits from QObject. QWidgets are inherited from QObject, so yes.
If you create a dialog, give all member pointer variables the dialog as parent and you don't have to care about their memory
With Qt the memory handling is a lot easier than with blank c++.
className(parameters, QObject parent);
am i right?
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2010-05-19
, 08:45
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Posts: 190 |
Thanked: 129 times |
Joined on Mar 2010
@ Bavaria, Germany
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#14
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Originally Posted by saxen
Not sure what you mean.
so in constructor method i've to define:
className(parameters, QObject parent);
am i right?
example implementation code:
Code:
MyClass::MyClass(QObject* parent)
: QObject(parent) // Not passing the parent to the QObject base will also result in memory leakage
{
mySubObject = new QObject(this); // Will be deleted when "MyClass" dies
myLeakObject = new QObject; // Will live forever
}
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2010-05-19
, 08:53
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Posts: 124 |
Thanked: 10 times |
Joined on Jan 2007
@ Italy
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#15
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Originally Posted by gri
yes, that's what i meant!! really thanks
Not sure what you mean.
example implementation code:
Code:MyClass::MyClass(QObject* parent) : QObject(parent) // Not passing the parent to the QObject base will also result in memory leakage { mySubObject = new QObject(this); // Will be deleted when "MyClass" dies myLeakObject = new QObject; // Will live forever }
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2010-05-19
, 13:46
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Posts: 124 |
Thanked: 10 times |
Joined on Jan 2007
@ Italy
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#16
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while i'm bothering you with this silly questions, i've another doubt about inclusions 
how to use #include? i mean it's different from java import, so using include(from what i remember) means include "piece of code"(correct if i'm wrong) and not just import a name space!
so, how to avoid duplicate include?
suppose i have main class, firstclass and secondclass, if i include secondclass in firstclass, and first class in main, does main class automatically include secondclass?
i hope u can understand what i'm trying to say
how to use #include? i mean it's different from java import, so using include(from what i remember) means include "piece of code"(correct if i'm wrong) and not just import a name space!
so, how to avoid duplicate include?
suppose i have main class, firstclass and secondclass, if i include secondclass in firstclass, and first class in main, does main class automatically include secondclass?
i hope u can understand what i'm trying to say
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2010-05-19
, 14:27
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Posts: 179 |
Thanked: 86 times |
Joined on Dec 2009
@ Barcelona
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#17
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Originally Posted by saxen
#include is macro directive, an it does what it says: *includes*. You'll make your program bigger in size
while i'm bothering you with this silly questions, i've another doubt about inclusions
how to use #include? i mean it's different from java import, so using include(from what i remember) means include "piece of code"(correct if i'm wrong) and not just import a name space!
so, how to avoid duplicate include?
suppose i have main class, firstclass and secondclass, if i include secondclass in firstclass, and first class in main, does main class automatically include secondclass?
i hope u can understand what i'm trying to say
#ifndef H_WHATEVER
#define H_WHATEVER
//CODE
#endif
Does this solve your problem?
PS:I'm too learning C++ to develop with Qt
| The Following User Says Thank You to damnshock For This Useful Post: | ||
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2010-05-19
, 17:11
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Posts: 190 |
Thanked: 129 times |
Joined on Mar 2010
@ Bavaria, Germany
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#18
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You can also use "#pragma once" instead of the ifndef guards. But this is not supported by every compiler.
So with ifndefs you are on the safe side, with pragma once you type less ... of course, you could also use both of them in one file.
So with ifndefs you are on the safe side, with pragma once you type less ... of course, you could also use both of them in one file.
| The Following User Says Thank You to gri For This Useful Post: | ||
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2010-05-19
, 18:50
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Posts: 726 |
Thanked: 345 times |
Joined on Apr 2010
@ Sweden
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#19
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Compilation of C++ (and C) happens in a couple of different steps:
- Preprocessor (handles #include, #define, #if, #ifdef and the like)
- Compiler (parses all the code and builds an abstract representation, AST, that's then changed in different ways for some kinds of optimization and other compiler magic)
- Generate assembler (the compiler backend translates the AST to platform specific assembler)
- Assembler (the assembler read the assembly code and translates it into object code with link references as special markers)
- Linker (links the compilation units (object code blobs) together and fixes link markers to reference shared libraries)
The preprocessor can be thought of as just a file manipulator that puts together the file that is to be parsed by the compiler. #include is a character by character insertion of another file.
As explained above, #ifdef is the classical way of preventing multiple includes.
- Preprocessor (handles #include, #define, #if, #ifdef and the like)
- Compiler (parses all the code and builds an abstract representation, AST, that's then changed in different ways for some kinds of optimization and other compiler magic)
- Generate assembler (the compiler backend translates the AST to platform specific assembler)
- Assembler (the assembler read the assembly code and translates it into object code with link references as special markers)
- Linker (links the compilation units (object code blobs) together and fixes link markers to reference shared libraries)
The preprocessor can be thought of as just a file manipulator that puts together the file that is to be parsed by the compiler. #include is a character by character insertion of another file.
As explained above, #ifdef is the classical way of preventing multiple includes.
| The Following User Says Thank You to Joorin For This Useful Post: | ||
If you create a dialog, give all member pointer variables the dialog as parent and you don't have to care about their memory
With Qt the memory handling is a lot easier than with blank c++.
PS: You could also take a look at QSharedPointer when using non-QObject classes. (or boost::shared_ptr if you don't like the Qt implementation)