module Warning

The Warning module contains a single method named warn, and the module extends itself, making Warning.warn available. Warning.warn is called for all warnings issued by Ruby. By default, warnings are printed to $stderr.

By overriding Warning.warn, you can change how warnings are handled by Ruby, either filtering some warnings, and/or outputting warnings somewhere other than $stderr. When Warning.warn is overridden, super can be called to get the default behavior of printing the warning to $stderr.

Public Class Methods

[](p1) click to toggle source


Warning[category]  -> true or false

Returns the flag to show the warning messages for category. Supported categories are:


deprecation warnings

  • assignment of non-nil value to $, and $;

  • keyword arguments

  • proc/lambda without block



experimental features

  • Pattern matching

static VALUE
rb_warning_s_aref(VALUE mod, VALUE category)
    rb_warning_category_t cat = rb_warning_category_from_name(category);
    if (rb_warning_category_enabled_p(cat))
        return Qtrue;
    return Qfalse;
[]=(p1, p2) click to toggle source


Warning[category] = flag -> flag

Sets the warning flags for category. See Warning.[] for the categories.

static VALUE
rb_warning_s_aset(VALUE mod, VALUE category, VALUE flag)
    unsigned int mask = rb_warning_category_mask(category);
    unsigned int disabled = warning_disabled_categories;
    if (!RTEST(flag))
        disabled |= mask;
        disabled &= ~mask;
    warning_disabled_categories = disabled;
    return flag;

Public Instance Methods

warn(msg) → nil click to toggle source

Writes warning message msg to $stderr. This method is called by Ruby for all emitted warnings.

static VALUE
rb_warning_s_warn(VALUE mod, VALUE str)
    Check_Type(str, T_STRING);
    return Qnil;