ruby - 替换 "\n"但不是 "\n\n"

Question

如何将 "\n" 而不是 "\n\n" 等替换为 "\n"？

text1 = "Hello\nWorld"
text1.sub! "\n", "  \n"
=> "Hello  \nWorld"

text2 = "Hello\n\nWorld"
text2.sub! "\n\n", "  \n"
=> "Hello  \n\nWorld"
SHOULD BE: => "Hello\n\nWorld"

Answer 1

您可以使用正则表达式 /(?<!\n)\n(?!\n)/ , 匹配 \n只有当它没有以另一个 \n 为前缀时并且后面没有 \n .

text1 = "Hello\nWorld"
# => "Hello\nWorld"
text1.sub /(?<!\n)\n(?!\n)/, "  \n"
# => "Hello  \nWorld"
text2 = "Hello\n\nWorld"
# => "Hello\n\nWorld"
text2.sub /(?<!\n)\n(?!\n)/, "  \n"
# => "Hello\n\nWorld"