method
underscore
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underscore(camel_cased_word)
public
Makes an underscored, lowercase form from the expression in the string.
Changes ‘::’ to ‘/’ to convert namespaces to paths.
Examples:
"ActiveModel".underscore # => "active_model" "ActiveModel::Errors".underscore # => "active_model/errors"
As a rule of thumb you can think of underscore as the inverse of camelize, though there are cases where that does not hold:
"SSLError".underscore.camelize # => "SslError"