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Entity Commands

Intermediate

A very common task is triggering slash commands (such as /playsound, or /summon) from inside Behavior Pack entities. This is a somewhat complicated topic, but once you get a handle on it, it isn’t that bad!

Animation Controllers

To trigger slash commands, we are going to use Behavior Pack animation controllers. Animation controllers should be placed like: animation_controllers/some_controller.json. You can learn more about animation controllers on the entity events section of bedrock.dev.

In short, animation controllers allow us to trigger events from behavior packs.

  • Slash commands (like /say)
  • Molang
  • Entity Events (such as namespace:my_event)

Here is an example animation controller:

{
    "format_version": "1.10.0",
    "animation_controllers": {
        "controller.animation.sirlich_entity_commands": {
            "states": {
                "default": {
                    "transitions": [
                        {
                            "on_summon": "1" //1 evaluates as true
                        }
                    ]
                },
                "on_summon": {
                    "on_entry": [
                        "/say I have been summoned"
                    ]
                }
            }
        }
    }
}

This animation controller will run the command /say I have been summoned as soon as the entity is summoned into the world. If you are confused about how this works, please review Molang, Animations, and Entity Events.

In short, there are states, which can trigger events in their on_entry clause. We use queries to move between different states. By default, entities will be inside of the default state.

WARNING: Queries are re-run when the world/chunk reloads. This means the line "/say I have been summoned" will actually run each time the entity “loads” -not only when it is summoned.

If you need to stop this from happening, you need to add additional queries, such as a skin_id query. The first time the entity spawns, check for skin_id = 0, and then also add some higher skin_id, such as skin_id = 1. Then, when the entity reloads, it won’t be able to run those commands. This is shown further down in the document.

Using Animation Controllers

To add this animation controller to our entity, we can use the following code in the entity definition description:

"description": {
    "identifier": "sirlich:entity_commands",
    "scripts": {
        "animate": [
            "sirlich:entity_commands"
        ]
    },
    "animations": {
        "sirlich:entity_commands": "controller.animation.sirlich_entity_commands"
    }
}

Once again, if you are confused about any of this step, please review the Entity Events documentation.

Triggering Commands using Events:

Animation transitions are created using queries. You can read about queries here. In our first example, our query was simply true, which means the commands run automatically. We can use more complicate queries to create more interesting effect. A really convenient method is using components as Molang filters to trigger the commands.

I personally like using skin_id.

We can update our animation controller to trigger based on skin_id:

{
    "format_version": "1.10.0",
    "animation_controllers": {
        "controller.animation.sirlich_entity_commands": {
            "states": {
                "default": {
                    "transitions": [
                        {
                            "command_example": "query.skin_id == 1"
                        },
                        {
                            "zombies": "query.skin_id == 2"
                        }
                    ]
                },
                "command_example": {
                    "transitions": [
                        {
                            "default": "query.skin_id != 1"
                        }
                    ],
                    "on_entry": [
                        "/say Command One!"
                        "@s execute_no_commands"
                    ]
                },
                "zombies": {
                    "transitions": [
                        {
                            "default": "query.skin_id != 2"
                        }
                    ],
                    "on_entry": [
                        "/say AHH! Zombies everywhere!",
                        "/summon minecraft:zombie",
                        "/summon minecraft:zombie",
                        "/summon minecraft:zombie",
                        "/summon minecraft:zombie"
                        "@s execute_no_commands"
                    ]
                }
            }
        }
    }
}

This animation controller has two command states now: The first is triggered by skin_id = 1, and the second by skin_id = 2. Note how I’ve added the @s execute_no_commands syntax at the end of each command list. We will create execute_no_commands later. It will allow us to set the skin_id back to 0, and re-use our commands.

The syntax is @s followed by the name of an entity event. This allows us to add/remove components from within the animation controller.

Setting Component Groups

Back in our entity file, we can set the skin_id using the skin_id component.

The skin_id component looks like this:

"minecraft:skin_id": {
    "value": 1
}

We can add component groups that contains skin_ids:

"component_groups": {
    "execute_no_commands": {
        "minecraft:skin_id": {
            "value": 0
        }
    },
    "command_example": {
        "minecraft:skin_id": {
            "value": 1
        }
    },
    "command_zombies": {
        "minecraft:skin_id": {
            "value": 2
        }
    }
}

Adding Events

Now lets create events so we can easily add these groups:

"events": {
    "minecraft:entity_spawned": {
        "add": {
            "component_groups": [
                "execute_no_commands"
            ]
        }
    },
    "execute_no_command": {
        "add": {
            "component_groups": [
                "execute_no_command"
            ]
        }
    },
    "command_example": {
        "add": {
            "component_groups": [
                "command_example"
            ]
        }
    },
    "command_zombies": {
        "add": {
            "component_groups": [
                "command_zombies"
            ]
        }
    }
}

Triggering Events

There are loads of ways to trigger events in Minecraft. Lets look at two specific examples:

Interact Component:

This component will spawn zombies whenever you click on him.

"minecraft:interact": {
    "interactions": [{
        "on_interact": {
            "filters": {
                "all_of": [{
                        "test": "is_family",
                        "subject": "other",
                        "value": "player"
                    }
                ]
            },
            "event": "command_zombie"
        }
    }]
}

Timer

This component will trigger the example command every 10 seconds:

"minecraft:timer": {
        "looping": true,
        "time": 1,
        "time_down_event": {
            "event": "example_command"
        }
    }

By adding these (and similar!) components to our entity, we can control when the skin_id changes, and therefor which events run.

Review:

Here is how it all works:

  • Run example_command using a component like interact or timer.
  • This adds the example_command component group
  • This adds the skin_id component
  • This sets the entities skin_id, which can be queried in the animation controller
  • The animation controller notices this skin_id, and moves to the example_command state
  • The animation controller runs the /say command
  • The animation controller runs the entity event @s execute_no_command
  • execute_no_command event sets the skin_id to 0
  • The animation controllers sees this, and transitions to the default state
  • Now the animation controller waits for a new skin_id