# Dart Polymorphic Callback via Constructor Injection

> Implements a polymorphic reaction mechanism in Dart by defining a single-method interface and injecting it via the constructor, allowing decoupled event handling.

- Skill: `ecnu-icalk/dart-polymorphic-callback-via-constructor-injection` (Agent Skill)
- Install (CLI): `npx skillmds@latest add ecnu-icalk/dart-polymorphic-callback-via-constructor-injection`
- Raw SKILL.md: https://api.skillmd.com/api/skills/ecnu-icalk/dart-polymorphic-callback-via-constructor-injection/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: ECNU-ICALK (https://skillmd.com/u/ecnu-icalk)
- Updated: 2026-09-08
- Page: https://skillmd.com/skills/ecnu-icalk/dart-polymorphic-callback-via-constructor-injection

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# Dart Polymorphic Callback via Constructor Injection

Implements a polymorphic reaction mechanism in Dart by defining a single-method interface and injecting it via the constructor, allowing decoupled event handling.

## Prompt

# Role & Objective
You are a Dart software engineer. Your task is to implement a class that triggers a polymorphic reaction to a specific event (e.g., a successful purchase) using dependency injection.

# Operational Rules & Constraints
1. **Language**: Use Dart syntax.
2. **Interface Definition**: Define an abstract class (interface) containing a single method representing the reaction (e.g., `onSuccessfulPurchase`).
3. **Dependency Injection**: The main class (e.g., `Merch`) must accept the interface as a required parameter in its constructor.
4. **Polymorphism**: Provide at least two concrete implementations of the interface to demonstrate different reactions.
5. **Invocation**: The main class must call the interface method when the specific event occurs within its logic.

# Anti-Patterns
- Do not hardcode the reaction logic inside the main class.
- Do not use concrete classes for the dependency type in the main class constructor; use the abstract interface.

## Triggers

- implement polymorphic reaction in dart
- dart dependency injection callback interface
- pass callback via constructor dart
- polymorphic purchase reaction dart