Emit Scopes¶

emit sends data into the NUClear system. The scope controls how that data is distributed.

Syntax¶

// Default (Local scope)
emit(std::make_unique<T>(args...));

// Explicit scope
emit<Scope::LOCAL>(std::make_unique<T>(args...));

// Scope with additional arguments
emit<Scope::DELAY>(std::make_unique<T>(args...), std::chrono::seconds(5));

Overview¶

Every emit call takes a std::unique_ptr to the data being emitted. The scope template parameter determines the distribution strategy. When no scope is specified, Scope::LOCAL is used.

Scopes cannot be combined — each emit call uses exactly one scope.

flowchart LR
    E["emit&lt;Scope&gt;(data)"]
    E --> L[Local]
    E --> I[Inline]
    E --> D[Delay]
    E --> Init[Initialise]
    E --> N[Network]
    E --> U[UDP]
    E --> W[Watchdog]

    L --> TP[Thread Pool]
    I --> CT[Current Thread]
    D --> Timer[ChronoController] --> TP
    Init --> Queue[Startup Queue] --> TP
    N --> Ser[Serialise] --> Net[NUClear Network]
    U --> Ser2[Serialise] --> Pkt[UDP Packet]
    W --> WD[Reset Timer]

Scopes¶

Scope	Description	Link
`Scope::LOCAL`	Distributes tasks via thread pool; stores data in global cache (default)	Local
`Scope::INLINE`	Executes reactions immediately on the emitter's thread	Inline
`Scope::DELAY`	Schedules a Local emit after a time delay	Delay
`Scope::INITIALIZE`	Queues data to be emitted during system startup	Initialise
`Scope::NETWORK`	Serializes and sends data to NUClear network peers	Network
`Scope::UDP`	Sends serialized data as a raw UDP packet	UDP
`Scope::WATCHDOG`	Services (resets) a watchdog timer	Watchdog