Model Editor

Use the model editor to create Universal Modeling Language (UML) style models with structured and behavioral diagrams that offer different views to your system. However, the editor uses a variant of UML and has only a subset of properties for specifying the appearance of model elements.

Structural diagrams represent the static aspect of the system and are therefore stable, whereas behavioral diagrams have both static and dynamic aspects.

You can create the following types of structural diagrams:

  • Package diagrams, which consist of packages and their relationships, and visualize how the system is packaged.
  • Class diagrams, which consists of classes, dependencies, inheritance, associations, aggregation, and composition, and show a system in an object-oriented way.
  • Component diagrams, which represent a set of components and their relationships, and show the implementation of a system.
  • Deployment diagrams, which represent a set of software and hardware components and their relationships, and visualize the deployment of a system.

You can create the following types of behavioral diagrams:

  • Use case diagrams, which consists of actors, use cases, and their relationships, and represent a particular functionality of a system.
  • Activity diagrams, which visualize the flow from one activity to another.
  • Sequence diagrams, which consist of instances and specify where the instances are activated and destroyed and where their lifeline ends.

Editing Models

You can create models that have several different structural or behavioral diagrams. You can add elements to the diagrams and specify properties for them. You can either use standard model elements or add your own elements with custom icons.

{Class diagram in the model editor}

A class diagram in the model editor.

You can add model elements to diagrams in the following ways:

  • Drag model elements from the element tool bar (1) to the editor (2).
  • Select tool bar buttons (3) to add elements to the element tree (4).
  • Drag elements from the element tree to the editor to add them and all their relations to the diagram.
  • Drag source files from the sidebar views to the editor to add C++ classes or components to diagrams.

Grouping Elements

You can group elements by surrounding them with a boundary. When you move the boundary, all elements within it are moved together. Similarly, drag a swimlane to the diagram. When you move the swimlane, all elements right to the swimlane (for vertical swimlanes) or below it (for horizontal swimlanes) will be moved together. A vertical swimlane is created when you drop the swimlane icon on the top border of the diagram and a horizontal swimlane is created when you drop the icon near the left border.

Classes or other objects that you lay on packages are moved with the packages. You can move individual elements and modify their properties (5) by selecting them. You can also use multiselection to group elements temporarily.

Aligning Elements

To align elements in the editor, select several elements and right-click to open a context menu. Select actions in the Align Objects menu to align elements horizontally or vertically or to adjust their width and height.

Managing Elements

Drag the mouse over elements to select them and apply actions such as changing their stereotype or color. A stereotype is a classifier for elements, such as entity, control, interface, or boundary. An entity is usually a class that is used to store data. For some stereotypes, a custom icon is defined. You can assign several comma-separated stereotypes to one element.

To add related elements to a diagram, select an element in the editor, and then select Add Related Elements in the context menu.

By default, when you select an element in a diagram, it is highlighted also in the Structure view. To change this behavior so that selecting an element in the Structure makes it highlighted also in the diagram, click and hold the button, and then select Synchronize Diagram with Structure. To keep the selections in the diagram and the Structure view synchronized, select Keep Synchronized.

Zooming into Diagrams

To zoom into diagrams, select the Zoom In toolbar button, press Ctrl++, or press Ctrl and roll the mouse wheel up. To zoom out of diagrams, select Zoom Out, press Ctrl+-, or press Ctrl and roll the mouse wheel down. To reset the diagram size to 100%, select Reset Zoom or press Ctrl+0.

Printing Diagrams

To print diagrams, press Ctrl+C when no elements are selected in the editor to copy all elements to the clipboard by using 300 dpi. Then paste the diagram to an application that can print images.

If you copy a selection of elements in the editor, only those elements and their relations will be copied to the clipboard as an image.

Exporting Diagrams as Images

To save diagrams as images, select File > Export Diagram. To save only the selected parts of a diagram, select Export Selected Elements.

Adding Custom Elements

The model editor has the following built-in element types: package, component, class, and item. For package, component, and class elements, you can specify custom icons. The color, size, and form of the icon are determined by a stereotype. If you attach the stereotype to an element, the element icon is replaced by the custom icon. For example, you can attach the entity and interface stereotypes to classes and the database stereotype to components.

The use case and activity diagrams are examples of using the built-in item element type to add custom elements. The item element has the form of a simple rectangle. The use case illustrates how to use a custom icon for an item. The attached stereotype is called usecase but it is hidden. Therefore, if you drag the use case to the diagram, it is shown as a use case but no stereotype appears to be defined and you can attach an additional stereotype to the use case.

Color and icons are attached to elements in use case and activity diagrams by using a simple definition file format. For example, the following code adds the UseCase custom element:

Icon {
    id: UseCase
    title: "Use-Case"
    elements: item
    stereotype: 'usecase'
    display: icon
    width: 40
    height: 20
    baseColor: #5fb4f0
    Shape {
        Ellipse { x: 20, y: 10, radiusX: 20, radiusY: 10 }

For more information about the available options, see standard.def in the share/qtcreator/modeleditor directory in the Qt Creator installation directory. It describes also how to define custom relation types and templates for existing types (such as a composition relation that can be drawn between classes).

You can add your own definition file and save it with the file extension .def to add custom colors and icons for stereotypes, elements, or tool bars. Either store this file in the same directory as the standard.def file or select the root element of a model and apply your .def file to the property Config path.

See also How To: Create Models and Diagrams, Create files, and Sidebar Views.

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