Activity Flows

Flows

A UML Activity Flow is a directed edge between Activity nodes. In Stateflows, a flow determines when its target can run and, for object flows, which tokens are offered to it. Flows are declared on their source node with AddControlFlow(...) or AddFlow<TToken>(...).

Flow kinds

Kind	Carries	Typical use
Control flow	A control token, not application data	Enable a target action or control node
Object flow	Values of a declared token type	Move application data between nodes
Transformation flow	Input values transformed to another type	Convert data while it traverses an edge

Guards, transformations, and weights

Object-flow guards inspect one token and decide whether that token traverses the edge. A transformation can replace it with another token type. SetWeight(n) sets the number of eligible tokens required on that flow before its target can activate.

.AddAction(
    "CreateRequest",
    async c => c.Output(new Request("ORD-42", 125)),
    b => b.AddFlow<Request>("Validate", flow => flow
        .AddGuard(async c => c.Token.Amount > 0)
        .AddTransformation(async c => c.Token.OrderId))
)
.AddAction(
    "Validate",
    async c =>
    {
        foreach (var orderId in c.GetTokensOfType<string>())
        {
            // Continue processing the validated order identifier.
        }
    })

Use a control flow when only execution order matters. Use an object flow when the target needs typed data. Its generic token type selects source tokens; a transformation can change the type delivered to the target.

Execution and token consumption

Flows do not all mean "run the target once for every edge." Nodes activate according to their incoming-flow rules and options. By default, Action nodes use implicit join and fork behavior; explicit Join, Merge, and Fork nodes make synchronization and branching visible in the graph. See Control Flow, Data Flow, and Implicit Fork and Join.

Related pages

• Nodes and Tokens
• Decision Node and Merge Node
• Fork Node and Join Node