Builder

GoF variant with Director orchestrating calls to the builder.

#When to use it

When you have reusable construction recipes (e.g., "PDF report", "Markdown report") and you want to encapsulate them.

public interface IReportBuilder
{
    void AddTitle(string t);
    void AddSection(string body);
    Report GetResult();
}

public class ReportDirector
{
    public void BuildExecutiveSummary(IReportBuilder b)
    {
        b.AddTitle("Executive Summary");
        b.AddSection("Quarterly KPIs...");
        b.AddSection("Risks...");
    }
}

#creational #director