Block comparison of class with ==

Usage like class(x) == "character" is prone to error since class in R is in general a vector. The correct version for S3 classes is inherits(): inherits(x, "character"). Often, class k will have an is. equivalent, for example is.character() or is.data.frame().

Usage

class_equals_linter()

Details

Similar reasoning applies for class(x) %in% "character".

See also

linters for a complete list of linters available in lintr.

Tags

best_practices, consistency, robustness

Examples

# will produce lints
lint(
  text = 'is_lm <- class(x) == "lm"',
  linters = class_equals_linter()
)
#> <text>:1:10: warning: [class_equals_linter] Use inherits(x, 'class-name'), is.<class> for S3 classes, or is(x, 'S4Class') for S4 classes, instead of comparing class(x) with ==.
#> is_lm <- class(x) == "lm"
#>          ^~~~~~~~~~~~~~~~

lint(
  text = 'if ("lm" %in% class(x)) is_lm <- TRUE',
  linters = class_equals_linter()
)
#> <text>:1:5: warning: [class_equals_linter] Use inherits(x, 'class-name'), is.<class> for S3 classes, or is(x, 'S4Class') for S4 classes, instead of comparing class(x) with %in%.
#> if ("lm" %in% class(x)) is_lm <- TRUE
#>     ^~~~~~~~~~~~~~~~~~

# okay
lint(
  text = 'is_lm <- inherits(x, "lm")',
  linters = class_equals_linter()
)
#> ℹ No lints found.

lint(
  text = 'if (inherits(x, "lm")) is_lm <- TRUE',
  linters = class_equals_linter()
)
#> ℹ No lints found.