instance method

Kernel#warn

(*::_ToS msg, ?uplevel: ::int?, ?category: ::Warning::category?) -> nil

warn(*msgs, uplevel: nil, category: nil) → nil

# File tmp/rubies/ruby-4.0.0/warning.rb, line 52
def warn(*msgs, uplevel: nil, category: nil)
  if Primitive.cexpr!("NIL_P(category)")
    Primitive.rb_warn_m(msgs, uplevel, nil)
  elsif Warning[category = Primitive.cexpr!("rb_to_symbol_type(category)")]
    Primitive.rb_warn_m(msgs, uplevel, category)
  end
end

If warnings have been disabled (for example with the -W0 flag), does nothing. Otherwise, converts each of the messages to strings, appends a newline character to the string if the string does not end in a newline, and calls Warning.warn with the string.

Example

warn("warning 1", "warning 2")

produces:

Example

warning 1
warning 2

If the uplevel keyword argument is given, the string will be prepended with information for the given caller frame in the same format used by the rb_warn C function.

Example

# In baz.rb
def foo
  warn("invalid call to foo", uplevel: 1)
end

def bar
  foo
end

bar

produces:

baz.rb:6: warning: invalid call to foo

If category keyword argument is given, passes the category to Warning.warn. The category given must be one of the following categories:

:deprecated: Used for warning for deprecated functionality that may be removed in the future.
:experimental: Used for experimental features that may change in future releases.
:performance: Used for warning about APIs or pattern that have negative performance impact

See also #URI #y #untrace_var #yield_self also in 4.1 · 3.4 · 3.3 · 3.2 · 3.1 · 3.0

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