### Tutorial

« Creating a Model | A Simple Example »

## Creating the View Component

While there are several different models to choose from, there is only one view widget to deal with. It works with either the list or the tree store. Setting up a TreeView is not a difficult matter. It needs a TreeModel to know where to retrieve its data from.
You can create a TreeView with one of the following constructors:

`TreeView(); explicit TreeView(Gtk::TreeModel& model);`

`
` You can set and get the model for the TreeView by calling:

`void set_model(Gtk::TreeModel *model); Gtk::TreeModel* get_model() const;`

Once the TreeView widget has a model, it will need to know how to display the model. It does this with columns and cell renderers.
Cell renderers are used to draw the data in the tree model in a way. There are three cell renderers that come with Inti. They are the CellRendererText, CellRendererPixbuf and CellRendererToggle. It is relatively easy to write a custom renderer.
The constructors for the three cell renderers are simple:

`CellRendererPixbuf(); CellRendererText(); CellRendererToggle();`

A TreeViewColumn is the object that TreeView uses to organize the vertical columns in the tree view. It needs to know the name of the column to label for the user, what type of cell renderer to use, and which piece of data to retrieve from the model for a given row.
You can create a TreeViewColumn by calling one of the following constructors:

`TreeViewColumn(); TreeViewColumn(const String& title, Gtk::CellRenderer *cell, ...); TreeViewColumn(const String& title, Gtk::CellRenderer& cell, const std::map<int, String>& attributes);`

The title is the title of the tree column and the cell is the cell to pack into the beginning of the tree column. The variable argument list is a null terminated list of tree column attributes to set. These should be in attribute(char*)/column(number)pairs. The last constructor takes a std::map of column(number)/attribute(String) pairs, the order being reversed because the column number is the key and the key must come first.
For example, to create a column using a list char*/column pairs you would do this:

`Gtk::CellRenderer *renderer = new Gtk::CellRendererText; Gtk::TreeViewColumn *column = new Gtk::TreeViewColumn ("Author", renderer, "text", AUTHOR_COLUMN, 0); tree_view->append_column(*column);`

and creating a column using a std::map<int, String> you would do this:

`#include <map> Gtk::CellRenderer *renderer = new Gtk::CellRendererText; std::map<int, String> attributes; attributes.insert(std::pair<int, String>(AUTHOR_COLUMN, "text")); Gtk::TreeViewColumn *column = new Gtk::TreeViewColumn("Author", *renderer, attributes);`

At this point, all the steps in creating a displayable tree have been covered. The model is created, data is stored in it, a tree view is created and columns are added to it.
Most applications will need to not only deal with displaying data, but also receiving input events from users. To do this, simply get a reference to a selection object and connect to the "changed" signal.

`// Setup the selection handler Gtk::TreeSelection *selection = tree_view->get_selection(); selection->set_mode (Gtk::SELECTION_SINGLE); selection->sig_changed().connect(slot(this, &MyClass::changed_handler));`

`
` where the changed_handler has the prototype:
`
`

`void MyClass::changed_handler();`

Then to retrieve data for the row selected:

`void MyClass::changed_handler() { Gtk::TreeModel *model = 0; Gtk::TreeIter iter; if (selection->get_selected(&model, &iter)) { String author; model->get_value(iter, AUTHOR_COLUMN, author); g_print ("You selected a book by %s\n", author); } }`

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