Builder

Builder

One-line pattern summary

A pattern that separates complex object creation into steps to improve readability and safety.

Typical Unity use cases

• When creating configuration objects with many options.
• When the same process produces different results.

Parts (roles)

• Builder
• Director (optional)
• Product

Unity example (C#)

The code below is a simplified Unity example based on the scenario described above.

public sealed class EnemyWaveConfig
{
    public int EnemyCount;
    public float SpawnIntervalSeconds;
    public string RewardId;
}

public sealed class EnemyWaveBuilder
{
    private readonly EnemyWaveConfig waveConfig = new();

    public EnemyWaveBuilder SetEnemyCount(int enemyCount)
    {
        waveConfig.EnemyCount = enemyCount;
        return this;
    }

    public EnemyWaveBuilder SetSpawnInterval(float spawnIntervalSeconds)
    {
        waveConfig.SpawnIntervalSeconds = spawnIntervalSeconds;
        return this;
    }

    public EnemyWaveBuilder SetReward(string rewardId)
    {
        waveConfig.RewardId = rewardId;
        return this;
    }

    public EnemyWaveConfig Build() => waveConfig;
}

Advantages

• Object creation responsibilities are well organized, which makes dependency management easier.
• Creation policies can be changed flexibly by environment or situation.

Things to watch out for

• Avoid introducing overly abstract creation layers for simple problems.
• As creation rules increase, keeping documentation and tests in sync becomes more important.

Interaction diagram

This shows the flow where a complex object is assembled step by step and returned at the end.