📜 Move Contract Development

Master the art of building scalable, secure Move smart contracts with Dubhe’s Entity Component System

Prerequisites: Basic understanding of blockchain concepts and programming. Complete the blockchain basics guide if you’re new to blockchain development.

🎯 What You’ll Learn

ECS Patterns

Build contracts using Entity Component System architecture

Move Best Practices

Write secure, gas-efficient Move code

Schema-Driven Development

Generate contracts automatically from schema definitions

📋 Development Overview

Dubhe transforms traditional smart contract development by introducing Entity Component System (ECS) architecture to blockchain applications. Instead of monolithic contracts, you build modular, composable systems.

Traditional Approach
Dubhe ECS Approach

// Monolithic player contract - hard to extend
module game::player {
    struct Player has key, store {
        id: UID,
        name: String,
        health: u64,
        level: u8,
        inventory: vector<Item>,
        position_x: u64,
        position_y: u64,
        experience: u64,
        // Adding new features requires modifying this struct
    }
    
    // All logic mixed together
    public fun create_player(...) { /* complex logic */ }
    public fun level_up(...) { /* more complex logic */ }
    public fun move_player(...) { /* even more logic */ }
    // Hard to test individual features
}

// Modular components - easy to extend
module game::components {
    struct HealthComponent has store, drop {
        current: u64,
        maximum: u64,
    }
    
    struct PositionComponent has store, drop {
        x: u64,
        y: u64,
    }
    
    struct ExperienceComponent has store, drop {
        current: u64,
        level: u8,
    }
}

// Focused systems - easy to test
module game::systems {
    public entry fun level_up_system(world: &mut World, entity: u64) {
        // Clean, focused logic
    }
    
    public entry fun movement_system(world: &mut World, entity: u64, dx: u64, dy: u64) {
        // Single responsibility
    }
}

🏗️ Development Workflow

Design Your Game Schema

Start with data structure design - this drives everything else.

# schemas/game.yaml
World: 
  components:
    HealthComponent:
      current: u64
      maximum: u64
    
    PositionComponent:
      x: u64  
      y: u64
    
    PlayerComponent:
      name: string
      owner: address
    
    InventoryComponent:
      items: "vector<u64>"
      capacity: u32
  
  systems:
    - CombatSystem
    - MovementSystem  
    - InventorySystem

Schema-First Development: Your schema definition automatically generates Move contracts, TypeScript types, and client SDK methods. This ensures type safety from blockchain to frontend.

Generate Base Contracts

# Generate Move contracts from schema
dubhe codegen

# Files created:
# - sources/codegen/world.move
# - sources/codegen/components/
# - sources/codegen/systems/

Generated World Contract

// Auto-generated world.move
module game::world {
    use sui::object::{Self, UID};
    use sui::table::{Self, Table};
    use sui::bag::{Self, Bag};
    
    struct World has key {
        id: UID,
        entities: Table<u64, EntityData>,
        next_entity_id: u64,
    }
    
    struct EntityData has store {
        components: Bag,
    }
    
    // Auto-generated helper functions
    public fun spawn_entity(world: &mut World): u64 { ... }
    public fun add_component<T: store>(world: &mut World, entity: u64, component: T) { ... }
    public fun get_component<T: store>(world: &World, entity: u64): &T { ... }
    // ... more helper functions
}

Implement Game Logic

Focus on the unique parts - Dubhe handles the boilerplate.

module game::combat_system {
    use game::world::{Self, World};
    use game::components::{HealthComponent, PlayerComponent};
    
    const EDamageExceedsHealth: u64 = 1;
    const ENotPlayerOwner: u64 = 2;
    
    public entry fun deal_damage(
        world: &mut World,
        target_entity: u64,
        damage_amount: u64,
        ctx: &TxContext
    ) {
        // Validate target exists
        assert!(world::has_component<HealthComponent>(world, target_entity), 0);
        
        // Apply damage
        let health = world::get_mut_component<HealthComponent>(world, target_entity);
        
        if (health.current > damage_amount) {
            health.current = health.current - damage_amount;
        } else {
            health.current = 0;
            
            // Add death marker for cleanup systems
            world::add_component(world, target_entity, DeadTag {});
            
            // Emit death event
            event::emit(PlayerDeathEvent {
                entity: target_entity,
                killer: tx_context::sender(ctx),
            });
        };
        
        // Emit damage event for frontend
        event::emit(DamageDealtEvent {
            target: target_entity,
            damage: damage_amount,
            remaining_health: health.current,
        });
    }
}

Build and Test

# Build contracts
dubhe build

# Run unit tests
dubhe test

# Start local blockchain for integration testing
dubhe node start

# Deploy to local network
dubhe deploy --network local

# Run integration tests
dubhe test --integration

🧩 Core ECS Concepts in Practice

Components: Pure Data Containers

Component Design Principles

Components should be small, focused data structures with no behavior.

// ✅ Good: Small, focused components
struct HealthComponent has store, drop {
    current: u64,
    maximum: u64,
}

struct PositionComponent has store, drop {
    x: u64,
    y: u64,
}

struct VelocityComponent has store, drop {
    dx: u64,  // velocity in x direction
    dy: u64,  // velocity in y direction
}

// ❌ Bad: Large, unfocused component
struct MegaPlayerComponent has store, drop {
    // Too many different concepts in one component
    health: u64,
    max_health: u64,
    position_x: u64,
    position_y: u64,
    velocity_x: u64,
    velocity_y: u64,
    level: u8,
    experience: u64,
    inventory_items: vector<u64>,
    equipment_weapon: u64,
    equipment_armor: u64,
    // ... this becomes unmaintainable
}

Systems: Pure Logic Functions

System Design Patterns

Systems are functions that operate on entities with specific component combinations.

module game::movement_system {
    use game::world::{Self, World};
    use game::components::{PositionComponent, VelocityComponent};
    
    // System processes all entities with Position + Velocity
    public entry fun update_movement(world: &mut World) {
        // This would be generated by Dubhe's query system
        let moving_entities = world::query_entities_with<PositionComponent, VelocityComponent>(world);
        
        let i = 0;
        while (i < vector::length(&moving_entities)) {
            let entity = *vector::borrow(&moving_entities, i);
            
            // Get components
            let position = world::get_mut_component<PositionComponent>(world, entity);
            let velocity = world::get_component<VelocityComponent>(world, entity);
            
            // Apply physics
            position.x = position.x + velocity.dx;
            position.y = position.y + velocity.dy;
            
            // Boundary checking
            if (position.x > MAX_WORLD_X) position.x = MAX_WORLD_X;
            if (position.y > MAX_WORLD_Y) position.y = MAX_WORLD_Y;
            
            i = i + 1;
        };
    }
    
    // System for player-initiated movement
    public entry fun move_entity(
        world: &mut World,
        entity: u64,
        new_x: u64,
        new_y: u64,
        ctx: &TxContext
    ) {
        // Validate ownership
        let player = world::get_component<PlayerComponent>(world, entity);
        assert!(player.owner == tx_context::sender(ctx), ENotOwner);
        
        // Validate position bounds
        assert!(new_x <= MAX_WORLD_X && new_y <= MAX_WORLD_Y, EInvalidPosition);
        
        // Update position
        let position = world::get_mut_component<PositionComponent>(world, entity);
        position.x = new_x;
        position.y = new_y;
        
        // Emit movement event
        event::emit(EntityMovedEvent {
            entity,
            old_x: position.x,
            old_y: position.y,
            new_x,
            new_y,
        });
    }
}

📚 Detailed Tutorial Series

🏗️ Step-by-Step Contract Development

Part 1: Project Setup

15 minutes • Initialize your Dubhe project, configure development environment, and understand the project structure.What you’ll learn:

Project initialization and configuration
Development environment setup
Understanding generated project structure
Configuring for multiple blockchain networks

Part 2: Local Development

10 minutes • Start a local blockchain node for rapid development and testing.What you’ll learn:

Starting local Sui/Aptos nodes
Network configuration and connection
Account management and funding
Basic deployment workflow

Part 3: Contract Implementation

30 minutes • Implement your first ECS-based game contracts with components and systems.What you’ll learn:

Schema design and code generation
Component implementation patterns
System function development
Event emission for frontend integration

Part 4: Testing Strategies

25 minutes • Write comprehensive tests for your Move contracts using Dubhe’s testing framework.What you’ll learn:

Unit testing individual components and systems
Integration testing with complete game scenarios
Test data setup and teardown
Performance and gas testing

Part 5: Deployment

20 minutes • Deploy your contracts to testnet and mainnet with proper verification.What you’ll learn:

Testnet deployment and verification
Mainnet deployment best practices
Contract verification on explorers
Post-deployment monitoring setup

🎮 Practical Examples

Example 1: Simple Combat System

Schema Definition
Generated Components
Combat System Implementation

# Combat system schema
components:
  HealthComponent:
    current: u64
    maximum: u64
  
  AttackComponent:
    damage: u64
    range: u64
    cooldown: u64
  
  DefenseComponent:
    armor: u64
    resistance: u8  # 0-100 percentage

systems:
  - CombatSystem

events:
  - DamageDealt
  - PlayerDeath
  - CombatAction

// Auto-generated component structs
module game::components {
    struct HealthComponent has store, drop {
        current: u64,
        maximum: u64,
    }
    
    struct AttackComponent has store, drop {
        damage: u64,
        range: u64,
        cooldown: u64,
    }
    
    struct DefenseComponent has store, drop {
        armor: u64,
        resistance: u8,
    }
}

module game::combat_system {
    use game::world::{Self, World};
    use game::components::{HealthComponent, AttackComponent, DefenseComponent};
    
    const ETargetOutOfRange: u64 = 1;
    const EAttackOnCooldown: u64 = 2;
    const EInsufficientHealth: u64 = 3;
    
    public entry fun attack(
        world: &mut World,
        attacker: u64,
        target: u64,
        ctx: &TxContext
    ) {
        // Validate attacker and target exist
        assert!(world::has_component<AttackComponent>(world, attacker), 0);
        assert!(world::has_component<HealthComponent>(world, target), 0);
        
        // Get attack stats
        let attack_stats = world::get_component<AttackComponent>(world, attacker);
        
        // Check range (simplified - in real game, check positions)
        // ... range checking logic ...
        
        // Calculate damage
        let base_damage = attack_stats.damage;
        let final_damage = if (world::has_component<DefenseComponent>(world, target)) {
            let defense = world::get_component<DefenseComponent>(world, target);
            calculate_damage_with_defense(base_damage, defense)
        } else {
            base_damage
        };
        
        // Apply damage
        let health = world::get_mut_component<HealthComponent>(world, target);
        if (health.current > final_damage) {
            health.current = health.current - final_damage;
        } else {
            health.current = 0;
            // Handle death
            handle_entity_death(world, target);
        };
        
        // Emit events
        event::emit(DamageDealtEvent {
            attacker,
            target,
            damage: final_damage,
            remaining_health: health.current,
        });
    }
    
    fun calculate_damage_with_defense(base_damage: u64, defense: &DefenseComponent): u64 {
        // Apply armor reduction
        let armor_reduced = if (base_damage > defense.armor) {
            base_damage - defense.armor
        } else {
            1 // Minimum 1 damage
        };
        
        // Apply resistance percentage
        let resistance_multiplier = 100 - (defense.resistance as u64);
        (armor_reduced * resistance_multiplier) / 100
    }
    
    fun handle_entity_death(world: &mut World, entity: u64) {
        // Add death component for cleanup systems
        world::add_component(world, entity, DeadComponent {
            death_time: tx_context::epoch_timestamp_ms(ctx),
        });
        
        // Emit death event
        event::emit(EntityDeathEvent {
            entity,
            death_time: tx_context::epoch_timestamp_ms(ctx),
        });
    }
}

Example 2: Inventory Management

Inventory Schema
Inventory System

components:
  InventoryComponent:
    items: "vector<u64>"  # Item entity IDs
    capacity: u32
  
  ItemComponent:
    name: string
    item_type: u8
    stack_size: u32
    rarity: u8
  
  EquipmentComponent:
    weapon: "Option<u64>"
    armor: "Option<u64>" 
    accessory: "Option<u64>"

systems:
  - InventorySystem
  - EquipmentSystem

module game::inventory_system {
    use std::option;
    use game::world::{Self, World};
    use game::components::{InventoryComponent, ItemComponent, EquipmentComponent};
    
    const EInventoryFull: u64 = 1;
    const EItemNotFound: u64 = 2;
    const EInvalidEquipmentSlot: u64 = 3;
    
    public entry fun pickup_item(
        world: &mut World,
        player_entity: u64,
        item_entity: u64,
        ctx: &TxContext
    ) {
        // Get player inventory
        let inventory = world::get_mut_component<InventoryComponent>(world, player_entity);
        
        // Check capacity
        assert!(vector::length(&inventory.items) < (inventory.capacity as u64), EInventoryFull);
        
        // Add item to inventory
        vector::push_back(&mut inventory.items, item_entity);
        
        // Remove item from world (it's now in inventory)
        world::remove_component<PositionComponent>(world, item_entity);
        
        // Emit pickup event
        event::emit(ItemPickupEvent {
            player: player_entity,
            item: item_entity,
            inventory_count: vector::length(&inventory.items),
        });
    }
    
    public entry fun equip_item(
        world: &mut World,
        player_entity: u64,
        item_entity: u64,
        equipment_slot: u8, // 0=weapon, 1=armor, 2=accessory
        ctx: &TxContext
    ) {
        // Validate item is in inventory
        let inventory = world::get_component<InventoryComponent>(world, player_entity);
        assert!(vector::contains(&inventory.items, &item_entity), EItemNotFound);
        
        // Get item type
        let item = world::get_component<ItemComponent>(world, item_entity);
        assert!(item.item_type == equipment_slot, EInvalidEquipmentSlot);
        
        // Get/create equipment component
        let equipment = if (world::has_component<EquipmentComponent>(world, player_entity)) {
            world::get_mut_component<EquipmentComponent>(world, player_entity)
        } else {
            world::add_component(world, player_entity, EquipmentComponent {
                weapon: option::none(),
                armor: option::none(),
                accessory: option::none(),
            });
            world::get_mut_component<EquipmentComponent>(world, player_entity)
        };
        
        // Handle equipment slot
        if (equipment_slot == 0) { // Weapon
            if (option::is_some(&equipment.weapon)) {
                // Unequip current weapon first
                let old_weapon = option::extract(&mut equipment.weapon);
                // Add old weapon back to inventory logic here
            };
            equipment.weapon = option::some(item_entity);
        } else if (equipment_slot == 1) { // Armor
            if (option::is_some(&equipment.armor)) {
                let old_armor = option::extract(&mut equipment.armor);
                // Handle old armor
            };
            equipment.armor = option::some(item_entity);
        };
        // ... handle other slots
        
        // Remove from inventory
        let (found, index) = vector::index_of(&inventory.items, &item_entity);
        if (found) {
            vector::remove(&mut inventory.items, index);
        };
        
        event::emit(ItemEquippedEvent {
            player: player_entity,
            item: item_entity,
            slot: equipment_slot,
        });
    }
}

🧪 Testing Your Contracts

Unit Testing Approach

Component Tests
System Tests

#[test_only]
module game::test_components {
    use game::components::{HealthComponent, AttackComponent};
    
    #[test]
    fun test_health_component_creation() {
        let health = HealthComponent {
            current: 100,
            maximum: 100,
        };
        
        assert!(health.current == 100, 0);
        assert!(health.maximum == 100, 0);
    }
    
    #[test]
    fun test_attack_component_values() {
        let attack = AttackComponent {
            damage: 25,
            range: 5,
            cooldown: 1000, // 1 second in milliseconds
        };
        
        assert!(attack.damage == 25, 0);
        assert!(attack.range == 5, 0);
        assert!(attack.cooldown == 1000, 0);
    }
}

#[test_only]
module game::test_combat {
    use game::world::{Self, World};
    use game::combat_system;
    use game::components::{HealthComponent, AttackComponent};
    
    #[test]
    fun test_basic_attack() {
        // Create test world
        let ctx = tx_context::dummy();
        let world = world::create_for_testing(&ctx);
        
        // Create attacker entity
        let attacker = world::spawn_entity(&mut world);
        world::add_component(&mut world, attacker, AttackComponent {
            damage: 30,
            range: 1,
            cooldown: 0,
        });
        
        // Create target entity
        let target = world::spawn_entity(&mut world);
        world::add_component(&mut world, target, HealthComponent {
            current: 100,
            maximum: 100,
        });
        
        // Execute attack
        combat_system::attack(&mut world, attacker, target, &ctx);
        
        // Verify damage was applied
        let health = world::get_component<HealthComponent>(&world, target);
        assert!(health.current == 70, 0); // 100 - 30 = 70
    }
    
    #[test]
    fun test_lethal_attack() {
        let ctx = tx_context::dummy();
        let world = world::create_for_testing(&ctx);
        
        let attacker = world::spawn_entity(&mut world);
        world::add_component(&mut world, attacker, AttackComponent {
            damage: 150, // More than target's health
            range: 1,
            cooldown: 0,
        });
        
        let target = world::spawn_entity(&mut world);
        world::add_component(&mut world, target, HealthComponent {
            current: 100,
            maximum: 100,
        });
        
        combat_system::attack(&mut world, attacker, target, &ctx);
        
        // Target should be dead
        let health = world::get_component<HealthComponent>(&world, target);
        assert!(health.current == 0, 0);
        
        // Death component should be added
        assert!(world::has_component<DeadComponent>(&world, target), 0);
    }
}

Integration Testing

// TypeScript integration tests
import { DubheClient, TestClient } from '@0xobelisk/dubhe-client';

describe('Contract Integration Tests', () => {
  let client: TestClient;
  
  beforeEach(async () => {
    client = await TestClient.setup();
  });
  
  it('should create player and attack monster', async () => {
    // Create player entity
    const player = await client.createEntity();
    await client.setComponent(player, 'HealthComponent', {
      current: 100n,
      maximum: 100n
    });
    await client.setComponent(player, 'AttackComponent', {
      damage: 25n,
      range: 1n,
      cooldown: 0n
    });
    
    // Create monster entity
    const monster = await client.createEntity();
    await client.setComponent(monster, 'HealthComponent', {
      current: 50n,
      maximum: 50n
    });
    
    // Execute attack
    await client.tx.combatSystem.attack({
      attacker: player,
      target: monster
    });
    
    // Verify results
    const monsterHealth = await client.getComponent('HealthComponent', monster);
    expect(monsterHealth.current).toBe(25n); // 50 - 25 = 25
  });
});

🚀 Advanced Patterns

State Machines with Components

AI State Management

// AI states as components
struct IdleState has store, drop {
    idle_duration: u64,
}

struct PatrolState has store, drop {
    current_waypoint: u64,
    patrol_path: vector<u64>,
}

struct AttackState has store, drop {
    target_entity: u64,
    attack_start_time: u64,
}

// AI system processes entities based on their current state
public entry fun ai_system(world: &mut World) {
    // Process idle entities
    let idle_entities = world::query_entities_with<IdleState>(world);
    process_idle_ai(world, idle_entities);
    
    // Process patrolling entities
    let patrol_entities = world::query_entities_with<PatrolState>(world);
    process_patrol_ai(world, patrol_entities);
    
    // Process attacking entities
    let attack_entities = world::query_entities_with<AttackState>(world);
    process_attack_ai(world, attack_entities);
}

Event-Driven Architecture

Cross-System Communication

// Events for system coordination
struct QuestCompletedEvent has copy, drop {
    player: u64,
    quest_id: u64,
    rewards: vector<u64>,
}

struct LevelUpEvent has copy, drop {
    player: u64,
    new_level: u8,
    skill_points: u8,
}

// Systems can react to events
public entry fun reward_system(world: &mut World) {
    // Process quest completion rewards
    // This would integrate with event listening in a real implementation
}

💡 Best Practices

Security Guidelines

Access Control

Always validate entity ownership before modifying components

Input Validation

Validate all function parameters and assert preconditions

Resource Management

Use Move’s resource safety to prevent duplication and loss

Event Emission

Emit events for all important state changes

Performance Optimization

Minimize Component Size

Keep components small to reduce gas costs

// ✅ Good: Small, focused component
struct PositionComponent has store, drop {
    x: u64, // 8 bytes
    y: u64, // 8 bytes
} // Total: 16 bytes

// ❌ Bad: Large component with unused fields
struct MegaComponent has store, drop {
    // Too much data in one component
    // Expensive to load when you only need position
}

Batch Operations

Process multiple entities in single function calls when possible

Optimize Queries

Structure your component queries for maximum efficiency

🎯 Next Steps

Start the Tutorial Series

Begin with project setup and work through each step

Join the Community

Get help from other developers and share your projects

Explore Examples

See a complete game implementation using these concepts

Advanced Concepts

Deep dive into ECS architecture patterns

​📜 Move Contract Development

​🎯 What You’ll Learn

ECS Patterns

Move Best Practices

Schema-Driven Development

​📋 Development Overview

​🏗️ Development Workflow

​🧩 Core ECS Concepts in Practice

​Components: Pure Data Containers

​Systems: Pure Logic Functions

​📚 Detailed Tutorial Series

​🏗️ Step-by-Step Contract Development

Part 1: Project Setup

Part 2: Local Development

Part 3: Contract Implementation

Part 4: Testing Strategies

Part 5: Deployment

​🎮 Practical Examples

​Example 1: Simple Combat System

​Example 2: Inventory Management

​🧪 Testing Your Contracts

​Unit Testing Approach

​Integration Testing

​🚀 Advanced Patterns

​State Machines with Components

​Event-Driven Architecture

​💡 Best Practices

​Security Guidelines

Access Control

Input Validation

Resource Management

Event Emission

​Performance Optimization

​🎯 Next Steps

Start the Tutorial Series

Join the Community

Explore Examples

Advanced Concepts

📜 Move Contract Development

🎯 What You’ll Learn

📋 Development Overview

🏗️ Development Workflow

🧩 Core ECS Concepts in Practice

Components: Pure Data Containers

Systems: Pure Logic Functions

📚 Detailed Tutorial Series

🏗️ Step-by-Step Contract Development

🎮 Practical Examples

Example 1: Simple Combat System

Example 2: Inventory Management

🧪 Testing Your Contracts

Unit Testing Approach

Integration Testing

🚀 Advanced Patterns

State Machines with Components

Event-Driven Architecture

💡 Best Practices

Security Guidelines

Performance Optimization

🎯 Next Steps