# Developer

> Developer API reference for Outpost

Category: OUTPOST · Source: https://miciomods.it/docs/ml-base-building-developer · Last updated: 2026-10-21

## Overview

Other resources integrate through server exports and the hooks in `open/server.lua`, `open/client.lua` and `open/shared.lua`. Hooks receive live data: treat `propData` and `prop` as read-only and return quickly.

> **WARNING:** Exports answer ml_ resources
>
> Most server exports answer only resources whose name starts with `ml_` and return `nil`, `false` or `{}` to any other caller. `IsReady`, `GetTotalCount`, `CountPropsByModel`, `GetGeneratorData` and the machine registration exports answer every resource.

```lua
local apiVersion = exports.ml_base_building:GetOpenApiVersion()
```

## Server Exports

### Pieces

- `IsReady()`: `true` once bases are loaded
- `GetActiveProps()`, `GetTotalCount()`: all placed pieces and their count
- `CountPropsByModel(model)`: pieces of one model
- `GetPropsByOwner(cid)`, `GetOwnerCount(cid)`: pieces of one character and their count
- `IsPropListComplete()`: `true` when every piece has loaded

### Flags and placement

- `GetFlagAtCoords(coords, bucket?)`, `GetFlagsAtCoordsBatch(list)`: the flag that covers a position
- `GetFlagInfo(flagId)`, `FlagExists(flagId)`, `IsFlagUnderRaid(flagId)`
- `CanBuildAt(cid, coords, bucket?)`: whether a character can build there
- `GetPlacementInfo(cid, coords, bucket?, permission?)`: flag, owner and permission result at a position
- `CanPlaceAt(cid, coords, bucket?, policy?)`, `CanPlaceAtSrc(src, coords, policy?)`: placement check for your own placeable objects

### Crews

- `GetCrewByCid(cid)`: the crew of a character, `{ id, name }`
- `IsCrewMember(crewId, cid)`, `GetCrewMemberCids(crewId)`
- `CrewPermHas(crewId, cid, permName)`: checks a permission from `shared/data/permissions.lua`, such as `'canBuild'`
- `GetCrewRaidLockUntil(crewId)`: end of the raid lock of a crew

### Generators and machines

- `GetGeneratorData(propId)`, `AddGeneratorFuel(propId, amount, fuelType)`
- `RegisterMachine(spec)`, `RegisterMachineVeto(fn)`, `SetMachineOffered(kind, offered)`, `PublishMachineCatalogue(list)`, `ReadoptMachines()`: let another resource add its own machines as base pieces
- `CanUseMachine(src, propId)`, `IsMachinePowered(propId)`, `GetMachineLife(propId)`, `RepairMachine(src, propId, amount)`, `GetMachineProps()`, `MachineCapabilities()`

### Beds

- `GetPlayerBeds(cid)`, `ResolveBedSpawn(cid, bedId)`, `ClaimRespawn(claim)`: base bed respawns for your death or spawn script

## Client Exports

- `IsBuildEntity(entity)`: `true` when the entity is a base piece
- `isSheltered()`: `true` while the player stands under a base roof
- `MLAdminOpen()`, `MLAdminPanel()`: open the admin panel, and its label and icon for a staff menu

## Server Hooks

Located in `open/server.lua`.

**open/server.lua**

```lua
function MLBB.Hooks.CanPlace(src, model, coords, flagId)
end

function MLBB.Hooks.CanDamage(attackerSrc, propData, damage, damageContext)
end
```

- `CanPlace`: return `false, localeKey` to refuse a placement. `nil` keeps the normal checks. An error or a first value that is not a boolean also refuses
- `CanDamage`: return `false` to refuse damage, or `true, newDamage` to replace it

Notification hooks, called after the action:

- `OnServerReady()`
- `OnPropPlaced(src, propData)`, `OnPropRemoved(src, propData, reason)`
- `OnPropDamaged(attackerSrc, propData, damage, lifeAfter, damageContext)`
- `OnDoorToggled(src, propData, isOpen)`, `OnStorageOpened(src, propData)`
- `OnGeneratorRefueled(src, propId, litres, fuelType, fuelAfter)`, `OnPowerChanged(propId, powered)`
- `OnExplosivePlanted(src, propData, itemName)`
- `OnFlagCreated(flagId, propId, ownerCid)`, `OnFlagRemoved(flagId)`

`src` can be `nil` for decay, server removals and offline attackers.

Providers, return `nil` to keep the default:

- `GetGameHour()`: game hour from 0 to 23, for solar output and `raidSchedule`
- `GetWeather()`: GTA weather name, for solar output
- `GetWindSpeed(propId, coords)`: wind speed for a turbine in m/s, 0 to 1000, from a trusted server weather resource. Output is speed divided by `ratedSpeed`

## Client Hooks

Located in `open/client.lua`.

- `OnClientReady()`
- `OnPropEnterRange(prop, entity)`, `OnPropExitRange(prop)`
- `OnPowerStateChanged(propId, powered)`, `OnDoorStateChanged(propId, isOpen)`
- `OnPlacementStarted(model)`, `OnPlacementConfirmed(model, propId)`, `OnPlacementEnded(model)`

## Server Events

- `ml_base_building:server:generatorNoise`: fired on the server for each running generator while `Config.Generator.noiseEnabled` is on, with `{ propId, coords, radius, bucket }`. A zombie or AI resource can listen to it

## Examples

**Block building near a hospital**

**open/server.lua**

```lua
function MLBB.Hooks.CanPlace(src, model, coords, flagId)
    if #(coords - vec3(298.0, -584.0, 43.0)) < 150.0 then
        return false, 'placement_disabled_zone'
    end
end
```

**Halve raid damage at night**

**open/server.lua**

```lua
function MLBB.Hooks.CanDamage(attackerSrc, propData, damage, damageContext)
    local hour = Bridge.GetGameTime() or 12
    if hour >= 22 or hour < 6 then
        return true, damage * 0.5
    end
end
```

**Check a crew permission from another resource**

The calling resource name must start with `ml_`.

**ml_yourscript/server.lua**

```lua
local crew = exports.ml_base_building:GetCrewByCid(cid)
if crew and exports.ml_base_building:CrewPermHas(crew.id, cid, 'canOpenStorages') then
end
```