claude-code-r-skills: Skill for Claude Code

R Object-Oriented Programming

S7, S3, S4, and vctrs: choosing the right OOP system for your needs

S7: Modern OOP for New Projects

• S7 combines S3 simplicity with S4 structure
• Formal class definitions with automatic validation
• Compatible with existing S3 code

# S7 class definition
Range <- new_class("Range",
  properties = list(
    start = class_double,
    end = class_double
  ),
  validator = function(self) {
    if (self@end < self@start) {
      "@end must be >= @start"
    }
  }
)

# Usage - constructor and property access
x <- Range(start = 1, end = 10)
x@start  # 1
x@end <- 20  # automatic validation

# Methods
inside <- new_generic("inside", "x")
method(inside, Range) <- function(x, y) {
  y >= x@start & y <= x@end
}

OOP System Decision Matrix

S7 vs vctrs vs S3/S4 Decision Tree

Start here: What are you building?

1. Vector-like objects (things that 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