CodeThousand Knowledge Base

Physical fitness for youth is divided into five trainable components and one observation metric. Each has specific developmental windows and training focuses:

Structural design patterns focus on how objects are composed to form larger structures, primarily by inserting an intermediary layer into the call chain. Common structural patterns include:

• Adapter: Converts interfaces to be compatible with existing code; used when integrating third-party or legacy components.
• Decorator: Adds behavior to a class without modifying its source; used for dynamically combining features like caching, logging, or retries.
• Proxy: Controls access to an object; used for lazy loading, permission control, or remote calls.
• Facade: Provides a simplified entry point to a complex subsystem; used to reduce external dependencies on internal logic.
• Composite: Treats single objects and compositions of objects uniformly; used for tree structures like menus, organizational charts, or expressions.
• Flyweight: Shares fine-grained objects to save memory; used when there are a large number of repetitive, immutable small objects.
• Bridge: Separates abstraction from implementation so they can vary independently; used when expanding across two dimensions simultaneously.

The Growth Tree framework organizes human development into three layers. The distinction between layers is based on the method of investment rather than importance. The framework is designed for children in Chinese-speaking households with parents who can commit consistent time and may experience periods of living abroad.

To use the framework, combine three axes:

1. Layer: Determines investment priority (prioritize the Root if resources are limited).
2. Stage: Aligns with specific age brackets (0–3, 3–6, 6–9, 9–12, 12–15, 15–18).
3. Domain: Categorized into Cognition, Emotion, and Skill (used for defining target behaviors).

Behavioral patterns focus on the distribution of responsibilities and communication methods between objects. Common behavioral patterns include:

• Strategy: Encapsulates interchangeable algorithms.
• Template Method: Defines a fixed process in a base class, allowing subclasses to implement specific steps.
• Observer: Implements one-to-many notifications (Publish-Subscribe).
• Chain of Responsibility: Passes requests along a chain where each node processes or forwards the request.
• State: Represents the state of an object and its transitions using objects.
• Command: Encapsulates a request as an object, enabling queuing, undo operations, and logging.
• Iterator: Provides a uniform way to traverse a collection without exposing its internal structure.
• Mediator: Uses a central object to coordinate interactions between multiple objects.
• Memento: Captures and restores an object's internal state.
• Visitor: Adds new operations to an element class without modifying the class itself.
• Interpreter: Represents a grammar as an object structure to evaluate expressions.

Creational patterns focus on how objects are created, with the primary goal of decoupling 'what is created' from 'how it is created'. Common patterns include:

• Factory Method: Allows subclasses to decide which class to instantiate; useful when types are determined by logic and are expected to increase over time.
• Abstract Factory: Creates families of related objects; useful when a set of implementations needs to be replaced as a suite (e.g., a UI component library).
• Builder: Constructs complex objects step-by-step; useful when there are many constructor parameters and various optional combinations.
• Prototype: Creates new objects by copying existing ones; useful when object creation is expensive and new objects are similar to existing ones.
• Singleton: Ensures a global unique instance; used when there is a genuine shared state, though it requires careful handling of concurrency and testing.