Execution Context Beginner

What is the Execution Context?

ISpcExecutionContext is created fresh each server tick and passed to every compiled node's execute(context, state) method. It provides read-only world access (sensors, inputs) and write-only world actions (outputs, effects, display messages).

All methods have safe defaults — if the physical multiblock doesn't support a feature (e.g., no FE modules), the method silently returns a neutral value or does nothing. Your node code never needs null-checks.

When is it available?

Digital I/O (2 methods)

Analog I/O (2 methods)

FE (Forge Energy) I/O (2 methods)

Virtual Signals (6 methods)

Virtual signals are named global variables shared across all nodes in a program. They're useful for cross-node communication without wires.

// Write a virtual signal from one node:
context.writeVirtualInteger("mymod:temperature", 350);

// Read it from another node (same tick, later phase):
int temp = context.readVirtualInteger("mymod:temperature");

Time (2 methods)

Display (2 methods)

World Sensors (9 methods)

// Example: Read nearby entities
int zombieCount = context.countEntitiesInRadius(32, "minecraft:zombie");

// Example: Check what block is nearby
boolean hasFurnace = context.isBlockAt(0, -1, 0, "minecraft:furnace");

Effects (4 methods)

Items (4 methods)

Data Logging (1 method)

Custom Module I/O (2 methods)

These methods bridge addon-registered multiblock modules (see Multiblock Modules) to the execution context. When a node needs to read from a custom input module or write to a custom output module, it uses these methods.

// Read from a custom rotational input module:
SpcSignalValue rpm = context.readCustomInput("mymod:rotational_input", 1);
int speed = rpm.asInteger();

// Write to a custom output module:
context.applyCustomOutputs("mymod:rotational_output",
    Map.of(1, SpcSignalValue.integer(targetSpeed)));

Extension Mechanism (1 method)

For complex world interactions that go beyond the built-in methods, addons register custom ISpcExecutionContextExtension implementations. See the Context Extensions guide for full details.

// In your compiled node:
Optional<ICreateRotationalContext> ext = context.getExtension(ICreateRotationalContext.class);
ext.ifPresent(rotCtx -> {
    int speed = rotCtx.getRotationalSpeed(blockPos);
    state.setSignal(outputAddr, SpcSignalValue.integer(speed));
});

Method Count Summary