Advanced C++ - Anonymous namespaces

Anonymous namespace is kind of namespace with no specified name. Such kind of namespace is visible only within file where it is defined within. I allows define variables and functions which could be visible as global, but within one file only. Thanks to that such files are not global within whole program. It also allow avoids making global static variable. Let's see an example of defining and usage of anonymous namespace. Consider following main.cpp file:
In the above example we have anonymous namespace containing one int typed variable. This variable can be used as global variable withing this main.cpp file but will not be visible inside any other files. That is simple example of usage anonymous variables. If you would like to compile it and play with it (changing or adding some parts of code to check what happends than) you can download it from here: https://github.com/xmementoit/CppAdventureExamples/tree/master/advancedCpp/anonymousNamespace

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QT - foreach algoriithm with const references performance improvement

Today I would like to show you optimal way of using foreach QT algorithm . I will show you why we should pass elements of foreach algorithm by const reference instead of passing them by value. Let me explain it on the below example: Output of this example is: In point I we are creating 3 objects of MyClass class and push them to myClasses QList element. In point II we are using QT foreach algorithm to invoke getValue() method for each object from myClasses list. As you can see on output text for that part of code we are invoking copy constructor before and destructor after invoking getValue() function. It is because we are passing each myClasses list element to foreach algorithm by value. Therefore we are copying that element at the beginning of foreach loop step and removing them (destructing) at the end. This is inefficient solution, especially when class of object being copied is big. It decreases performance. of our application. Solution for that i...

Advanced C++ - Compiler generated functions

When we define some class in our C++ code, compiler is generating some important functions for our class (unless we define it explicitly). Those functions (sometimes called Compiled Generated Functions ) are: default constructor destructor copy constructor copy assignment operator During compilation, compiler knows our code and classes usage, so when we are using one of above functions implicitly, it generate that function implicitly for us in the class body. For better explenation, let's see the example below: In point (I) we are defining class TestClass . This class seems to be empty. However we are implicitly using following function in main class: point III - we are implicitly using defualt constructor in order to create instance of TestClass - default constructor of TestClass is implicitly generated by compiler point IV - we are using copy constructor of TestClass in order to copy instance to...

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