字符串:使用*符号屏蔽最后n个字符

Zec*_*eck 1 ruby string ruby-on-rails ruby-on-rails-4

我有一个以下字符串:

99001155
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我想用*符号掩盖最后4个字符.例如:

99001155 - > 9900****

怎么做?

Ama*_*dan 7

str = "99001155"
str[-4..-1] = "****"
str
# => 9900****
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