TechTalk 20250611: Factory Pattern - Separating Creation from Use

Wed, 11 Jun 2025 13:28:15 +0000

At its core, the Factory Pattern centralizes object creation into dedicated methods or classes, instead of scattering new calls or complex constructors throughout your codebase. This separation yields several benefits:

Clarity of Intent
A method named CreateFromCsv() or ConfigureNumberDisplay() immediately tells the reader what kind of object will emerge, whereas a bare constructor new TextDisplayConfiguration(…) may require you to look up parameter lists and defaults.
Flexible Return Types
Static factory methods can return any subtype or cached instance they choose. A constructor must always return a fresh instance of its own class.
Simplified Overloads
Instead of dozens of overloaded constructors to cover different initialization scenarios, you provide a handful of well-named static methods (e.g. WithTitle(), WithSubtitle()), each encapsulating its own logic and defaults.
Validation and Caching
Factories can centralize validation (throw early on bad arguments), perform expensive setup only once (returning a shared singleton), or even pool and reuse objects.

Static Factory Methods vs Constructors

Aspect	Constructors	Static Factory Methods
Naming & Discoverability	No name beyond class name	Method names describe purpose
Return Flexibility	Fixed to class it belongs to	Can return subtypes or cached refs
Overload Explosion	Many overloads → unreadable	Distinct methods → self-documented
Default Configuration Logic	Scattered in callers	Encapsulated in one place
Conditional Instantiation	Hard to vary at runtime	Easy to branch inside factory

Divooka's Use Case: Organizing Tools by Category

In Divooka, every static method in a class becomes a toolbox entry - with the class name serving as the toolbox category. By grouping related factory methods inside dedicated static class containers (e.g. PlotConfigurations), Divooka can automatically:

Discover all available tools at startup
Organize them under logical headings (one class = one category)
Expose named methods like ConfigureTextDisplayWithTitleAndSubtitle directly to end-users

Were these methods instead constructors on each configuration type, Divooka would lack a natural grouping: you'd have to scan every class for all its constructors, losing that simple "category = class" mapping based on usage.

Case Study: ASP .NET Core's Builder-Based Factory Approach

ASP .NET Core also relies heavily on factories - but often via the builder pattern:

Host.CreateDefaultBuilder(args)
    .ConfigureServices((ctx, services) =>
    {
        services.AddDbContext<MyDbContext>(opts => 
            opts.UseSqlServer(connectionString));
        services.AddSingleton<IMyService, MyService>();
    })
    .Build();

Here the "factory" is implicit in the IHostBuilder:

Fluent configuration methods (ConfigureServices, UseUrls, etc.) collect options
The final Build() call manufactures the fully wired IHost
You get immutability until build time, plus a clear sequence of configuration steps

Comparing Static vs. Builder Factories

Feature	Static Factory Methods	Builder Pattern (ASP NET Core)
Discovery	Simple reflection on static classes	Extension-method based; discoverable by IDE but less obvious at runtime
Grouping	One class = one category	Spread across many fluent calls
Extensibility	Add new methods in classes	Add new extension methods on interfaces
Configurability	Encapsulated per-method logic	Centralized in a mutable builder state
Readability	Direct: `MyFactory.Create(…)`	Fluent chaining: `builder.Configure…`

In many small‐to‐medium scenarios, static factory methods win on simplicity: you immediately see each creation scenario, and end-users can invoke exactly what they need. In very large frameworks (like ASP .NET Core), the builder shines by aggregating dozens of configuration concerns into a single, coherent pipeline before creating the final product.

Conclusion

The Factory Pattern - whether via simple static methods or a full builder API - decouples what you need from how it's built. Choosing static factory methods:

Keeps creation logic in one readable place
Leverages method naming to self-document different initialization paths
Allows frameworks like Divooka to auto-discover and categorize tools
Avoids constructor overload chaos