jeremy-allen/claude-skills/designing-oop-r

Designing OOP R

This skill covers object-oriented programming in R, including S7, S3, S4, and vctrs-based classes.

Decision Tree: What Are You Building?

1. Vector-like objects (behave like atomic vectors)

Use vctrs when:

• Need data frame integration (columns/rows)
• Want type-stable vector operations
• Building factor-like, date-like, or numeric-like classes
• Need consistent coercion/casting behavior
• Working with existing tidyverse infrastructure

Examples: custom date classes, units, categorical data

2. General objects (complex data structures, not vector-like)

Use S7 when:

• NEW projects that need formal classes
• Want property validation and safe property access (@)
• Need multiple dispatch (beyond S3's double dispatch)
• Converting from S3 and want better structure
• Building class hierarchies with inheritance
• Want better error messages and discoverability

Use S3 when:

• Simple classes with minimal structure needs
• Maximum compatibility and minimal dependencies
• Quick prototyping or internal classes
• Contributing to existing S3-based ecosystems
• Performance is absolutely critical (minimal overhead)

Use S4 when:

• Working in Bioconductor ecosystem
• Need complex multiple inheritance (S7 doesn't support this)
• Existing S4 codebase that works well

S7 vs S3 Comparison

S7: Modern OOP

S7 combines S3 simplicity with S4 structure. See s7-examples.md for:

• Class definitions with new_class()
• Property validation
• Generic and method definition
• Inheritance with parent

S3: Simple Classes

See s3-examples.md for:

• Constructor functions
• Print and format methods
• Simple class patterns

Practical Guidelines

Choose S7 when you have:

See when-s7.md for:

• Complex validation needs
• Multiple dispatch needs
• Class hierarchies with clear inheritance

Choose vctrs when you need:

See when-vctrs.md for:

• Vector-like behavior in data frames
• Type-stable operations

Choose S3 when you have:

See when-s3.md for:

• Simple classes without complex needs
• Maximum performance needs (rare)
• Existing S3 ecosystem contributions

Migration Strategy

1. S3 → S7: Usually 1-2 hours work, keeps full compatibility
2. S4 → S7: More complex, evaluate if S4 features are actually needed
3. Base R → vctrs: For vector-like classes, significant benefits
4. Combining approaches: S7 classes can use vctrs principles internally

source: Sarah Johnson's gist https://gist.github.com/sj-io/3828d64d0969f2a0f05297e59e6c15ad