大写只包含字符串中的4个字符

Question

如何才能在Ruby中以字符串大写形式生成最后4个字符？

Answer 1

s = 'string'
"#{s[0..-5]}#{s[-4..-1].upcase}" # => stRING

要防止字符串短于4个字符的错误，您可以这样做：

s = 'foo'
s.length > 4 ? "#{s[0..-5]}#{s[-4..-1].upcase}" : s.upcase # => FOO

查看Ruby API以获取解释。

Answer 2

str = "let's upcase last 4 letters"
length = str.length
str = str[0..(length-5)] + str[(length-4)..length].upcase
# let's upcase last 4 letTERS

Answer 3

<强>更新

s = "string"
s.size > 3 ? s[0..-5]+s[-4..-1].upcase : s.upcase # "stRING"