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System Class

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A class that provides system-level events and functions.

Properties

afterEvents

read-only afterEvents: SystemAfterEvents;

Returns a collection of after-events for system-level operations.

Type: SystemAfterEvents

beforeEvents

read-only beforeEvents: SystemBeforeEvents;

Returns a collection of before-events for system-level operations.

Type: SystemBeforeEvents

Caution

This property is still in pre-release. Its signature may change or it may be removed in future releases.

currentTick

read-only currentTick: number;

Represents the current world tick of the server.

Type: number

Methods

clearJob

clearJob(jobId: number): void

Cancels the execution of a job queued via System.runJob.

Parameters

  • jobId: number

    The job ID returned from System.runJob.

Caution

This function is still in pre-release. Its signature may change or it may be removed in future releases.

clearRun

clearRun(runId: number): void

Cancels the execution of a function run that was previously scheduled via System.run.

Parameters

  • runId: number

run

run(callback: () => void): number

Runs a specified function at the next available future time. This is frequently used to implement delayed behaviors and game loops. When run within the context of an event handler, this will generally run the code at the end of the same tick where the event occurred. When run in other code (a system.run callout), this will run the function in the next tick. Note, however, that depending on load on the system, running in the same or next tick is not guaranteed.

Parameters

  • callback: () => void

    Function callback to run at the next game tick.

Returns number - An opaque identifier that can be used with the clearRun function to cancel the execution of this run.

Examples

trapTick.ts
import { system, world } from '@minecraft/server';

function printEveryMinute() {
    try {
        // Minecraft runs at 20 ticks per second.
        if (system.currentTick % 1200 === 0) {
            world.sendMessage('Another minute passes...');
        }
    } catch (e) {
        console.warn('Error: ' + e);
    }

    system.run(printEveryMinute);
}

printEveryMinute();

runInterval

runInterval(callback: () => void, tickInterval?: number): number

Runs a set of code on an interval.

Parameters

  • callback: () => void

    Functional code that will run when this interval occurs.

  • tickInterval?: number = null

    An interval of every N ticks that the callback will be called upon.

Returns number - An opaque handle that can be used with the clearRun method to stop the run of this function on an interval.

Examples

every30Seconds.ts
import { system, world } from '@minecraft/server';

const intervalRunIdentifier = Math.floor(Math.random() * 10000);

system.runInterval(() => {
    world.sendMessage('This is an interval run ' + intervalRunIdentifier + ' sending a message every 30 seconds.');
}, 600);

runJob

runJob(generator: Generator<void, void, void>): number

Queues a generator to run until completion. The generator will be given a time slice each tick, and will be run until it yields or completes.

Parameters

  • generator: Generator<void, void, void>

    The instance of the generator to run.

Returns number - An opaque handle that can be used with System.clearJob to stop the run of this generator.

Caution

This function is still in pre-release. Its signature may change or it may be removed in future releases.

Examples

cubeGenerator.ts
import { BlockPermutation, DimensionLocation, world, ButtonPushAfterEvent, system } from '@minecraft/server';

// A simple generator that places blocks in a cube at a specific location
// with a specific size, yielding after every block place.
function* blockPlacingGenerator(blockPerm: BlockPermutation, startingLocation: DimensionLocation, size: number) {
    for (let x = startingLocation.x; x < startingLocation.x + size; x++) {
        for (let y = startingLocation.y; y < startingLocation.y + size; y++) {
            for (let z = startingLocation.z; z < startingLocation.z + size; z++) {
                const block = startingLocation.dimension.getBlock({ x: x, y: y, z: z });
                if (block) {
                    block.setPermutation(blockPerm);
                }
                yield;
            }
        }
    }
}

// When a button is pushed, we will place a 15x15x15 cube of cobblestone 10 blocks above it
world.afterEvents.buttonPush.subscribe((buttonPushEvent: ButtonPushAfterEvent) => {
    const cubePos = buttonPushEvent.block.location;
    cubePos.y += 10;

    const blockPerm = BlockPermutation.resolve('minecraft:cobblestone');

    system.runJob(blockPlacingGenerator(blockPerm, { dimension: buttonPushEvent.dimension, ...cubePos }, 15));
});

runTimeout

runTimeout(callback: () => void, tickDelay?: number): number

Runs a set of code at a future time specified by tickDelay.

Parameters

  • callback: () => void

    Functional code that will run when this timeout occurs.

  • tickDelay?: number = null

    Amount of time, in ticks, before the interval will be called.

Returns number - An opaque handle that can be used with the clearRun method to stop the run of this function on an interval.