对于那些不使用rails处理小数的人来说，更好的方法是:

parts = number.to_s.split('.')
parts[0].gsub!(/(\d)(?=(\d\d\d)+(?!\d))/, "\\1,")
parts.join('.')

如果需要不同的分隔符，请更改正则表达式中的最后一个'，'。

额外的，这是正则表达式的工作方式:

gsub replaces everything that matches the regex with the second parameter passed to gsub. In this case that is \\1. \\1 becomes \1 when evaluated which matches the first capture group in the regex. In this regex that is (\d). (\d)(?=(\d\d\d)+) is matching a digit followed by 1 or more groups of 3 digits. The first set of parens is our \1 capture group, the second would be \2. If we were just to leave it at that we would get: 123456.gsub!(/(\d)(?=(\d\d\d)+)/, "\\1,") #=> 1,2,3,456 This is because 1234 matches, 2345 matches and 3456 matches so we put a comma after the 1, the 2, and the 3. By adding the (?!\d) we are matching anything that comes before that doesn't precede a digit so (\d)(?=(\d\d\d)+(?!\d)) means match a digit followed by 3 digits that is not followed by a digit. The reason why this works is that gsub will keep replacing things that match the string. If we were only going to replace the first match then for a number like 123456789 we would get 123456,789. Since 123456,789 still matches our regex we get 123,456,789.

这是我得到代码的地方:https://github.com/rails/rails/blob/master/activesupport/lib/active_support/number_helper.rb#L298-L300

这里是我了解正则表达式中发生了什么的地方:http://www.tutorialspoint.com/ruby/ruby_regular_expressions.htm

是的，使用NumberHelper。您正在寻找的方法是number_with_delimiter。

 number_with_delimiter(98765432.98, :delimiter => ",", :separator => ".")
 # => 98,765,432.98

您需要使用number_with_delimiter方法。例如:

<%= number_with_delimiter(@number, :delimiter => ',') %>

或者，你也可以使用number_with_precision方法来确保数字总是以小数点后两位的精度显示:

<%= number_with_precision(@number, :precision => 2, :delimiter => ',') %>

对于Ruby Folks:可以创建函数将逗号设置为大整数。

def number_with_comma(numStr)
   return numStr.to_s.gsub(/\B(?=(...)*\b)/, ',')
end
a = number_with_comma 1234567
puts a   => 1,234,567

x = 9876543
y = number_with_comma x
puts y   => 9,876,543

如果您希望在视图之外添加逗号，并且不想包含某些模块，则可以使用number_to_delimited方法(rails version >= 4.02)。例如:

#inside anywhere
ActiveSupport::NumberHelper.number_to_delimited(1000000) # => "1,000,000"

对于不使用rails的人:

number.to_s.reverse.gsub(/(\d{3})(?=\d)/, '\\1,').reverse