Claude-Tools-for-Delphi: Skill for Claude Code

Delphi refactoring — reference

Refactoring changes structure, not behaviour. The only proof of that is a test that is green before and stays green after. If the code under change has no test, write one first (/light-review-RedGreen) — otherwise you are rewriting, not refactoring.

Safe process

1. Green baseline — the relevant DUnitX tests pass now.
2. One small step at a time — never batch unrelated moves.
3. Compile only via the light-compiler agent (global CLAUDE.md rule), then re-run the test EXE.
4. Reuse before you write: a LightCore.* / LightVcl.* / LightFmx.* unit may already do it.

Catalog

Extract Method — long method / duplicated block

Pull a named block into its own method. Target ≤ ~20 lines, one level of abstraction. Name it after what it does, not how.

Extract Class — a class doing several jobs

When a class holds two unrelated clusters of fields+methods, split the second cluster into its own class and hold it by composition. This is the usual fix for a god class (see /light-code-ArchitectureClass).

Replace Nested Conditionals with Guard Clauses

Invert edge cases into early Exit/raise at the top so the happy path runs unindented.

procedure Process(AOrder: TOrder);
begin
  if not Assigned(AOrder) then raise EArgumentNil.Create('AOrder');
  if AOrder.Items.Count = 0 then raise EBusinessRule.Create('empty order');
  // happy path, no nesting
end;

Replace Magic Number/String with Named Constant

const MINIMUM_AGE = 18; — the name documents intent and kills duplication.

Replace Conditional with Polymorphism

A case/if ladder that switches on a type or state and recurs in several places → move each branch into a virtual method on a small class family (Strategy/State). See /light-ref-DesignPatterns.

Introduce Parameter Object

Three-plus parameters that always travel together → gather them into a record (value type, no lifetime to manage) and pass that.

Remove with

Replace every with X do ... with an explicit X. prefix (or a short local alias). with hides which scope a name binds to and defeats the IDE.