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C++ Tour Part III

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Shared Pointer A  shared  pointer is a smart pointer that allows for distributed ownership of data. Each time it is assigned, a  reference count  is incremented, indicating one more owner of the data. When the pointer goes out of scope or an owner calls  reset , the reference count is decremented. When the reference count goes to 0, the data pointed to is deallocated. Use  make_shared : auto person = std :: make_shared < Person > ( ) ; if ( person ) { cout << "Person's address is " << person -> address ; } C++17 allows use of shared pointers to point to dynamically allocated arrays. However,  make_shared  cannot be used. Below is an example: shared_ptr < Person [ ] > persons ( new Person [ 10 ] ) ; persons [ 0 ] . _name = "Jack Sparrow" ; persons [ 0 ] . _address = "Caribbean" ; cout << "Address of first person " << persons [ 0 ] . address << endl ; A better solutio...
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C++ Tour Part I

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C++ Tour Hello World Here is the hello world program for C++: # include <iostream> int main ( ) { std :: cout << "Hello, World" << std :: endl ; return 0 ; } Building a C++ Program Building a C++ program is a three step process: Code is run through  preprocessor  which processes meta information The code is  compiled  where each .cpp file is translated to .o object file Individual object files are  linked  together into a single application. Main function Main function is where program execution starts. It comes in two flavors: with and without arguments. With arguments, it looks as follows: int main ( int argc , char * argv [ ] ) where  argc  gives the number of commandline arguments to the program, and  argv  array contains those arguments. The actual arguments start from index 1. I/O Streams cout  is the stream for standard output,  cerr  is the strea...
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QTreeView and QTableView dynamic changes

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Dynamically adding items to  QTreeView  and  QTableView Create the UI as follows, with the treeview on the left hand side and the table view on the right hand side. Notes The header file contains the models and the selection models for the tree view and the table view: QStandardItemModel * treeViewModel ; QItemSelectionModel * treeViewSelectionModel ; QItemSelectionModel * tableSelectionModel ; QStandardItemModel * tableModel ; In the .cpp file, the tree view models and table view models are set as the models for the selection models. treeViewSelectionModel -> setModel ( treeViewModel ) ; tableSelectionModel -> setModel ( tableModel ) ; The following code illustrates how to dynamically add a new row to the treeview. void MainWindow :: updateTreeView ( ) { QStandardItem * newRow = new QStandardItem ( QString ( "inserted row" ) ) ; QList < QStandardItem * > newRows ; newRows . append ( newRow ) ; aut...
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