The data flow model automates data propagation between nodes. When a node's output changes, connected nodes automatically receive the new data. The system consists of three components:
- DataFlowGraphModel: Manages nodes and routes data.
- NodeDelegateModel: Contains your specific node logic (one class per node type).
- NodeDelegateModelRegistry: A factory used to create node instances.
To implement a data flow application, you must define a custom NodeData type, create a NodeDelegateModel for your node logic, and register these nodes in a NodeDelegateModelRegistry before passing the registry to a DataFlowGraphModel.
#include <QtNodes/NodeData>
#include <QtNodes/NodeDelegateModel>
#include <QtNodes/NodeDelegateModelRegistry>
// 1. Define data type
class NumberData : public QtNodes::NodeData {
public:
NumberData(double value = 0.0) : _value(value) {}
QtNodes::NodeDataType type() const override { return {"number", "Number"}; }
double value() const { return _value; }
private:
double _value;
};
// 2. Create node delegate
class AdditionNode : public QtNodes::NodeDelegateModel {
Q_OBJECT
public:
QString caption() const override { return "Add"; }
QString name() const override { return "Addition"; }
unsigned int nPorts(PortType type) const override { return type == PortType::In ? 2 : 1; }
NodeDataType dataType(PortType, PortIndex) const override { return NumberData{}.type(); }
void setInData(std::shared_ptr<NodeData> data, PortIndex port) override;
std::shared_ptr<NodeData> outData(PortIndex) override;
QWidget* embeddedWidget() override { return nullptr; }
private:
std::shared_ptr<NumberData> _input1, _input2, _result;
};
// 3. Register and create model
auto registry = std::make_shared<NodeDelegateModelRegistry>();
registry->registerModel<NumberSourceNode>("Sources");
registry->registerModel<AdditionNode>("Operators");
registry->registerModel<DisplayNode>("Outputs");
DataFlowGraphModel model(registry);
DataFlowGraphicsScene scene(model);
