Ruby:子串到一定长度,也在子串中持续空格

Question

我试图将一长串文本截断到一定长度,但也希望确保截断的结果在空格处结束.之后我还要附加一个省略号.

例如:

"This is a very long string that has more characters than I want in it."

成为这个:

"This is a very long string that..."

我从这开始,但显然这不涉及在空格上结束字符串的问题.

<%= item.description[0..30] %>&hellip;

Answer 1

如果你使用的是Rails 4+,你应该使用内置的truncate帮助方法,例如:

<%= truncate item.description, length: 30, separator: /\w+/ %>

字符串"..."将附加到截断的文本; 要指定不同的字符串,请使用:omission选项,例如omission: "xxx".

对于Rails 3.x,:separator选项必须是字符串.:separator => " "在许多情况下,给予会很好,但只能抓住空间而不是其他空白.一个折衷方案是使用String#squish,它用一个空格替换所有空白序列(并且还修剪前导和尾随空格),例如"foo\n\tbar ".squish产量"foo bar".它看起来像这样:

<%= truncate item.description.squish, :length => 30, :separator => /\w/,
                                      :omission => "&hellip;" %>

Answer 2

s[0..30].gsub(/\s\w+\s*$/, '...')

原始答案在30个字符子串以空白字符结束的情况下不起作用.这解决了这个问题.

>> desc="This is some text it is really long"

>> desc[0..30].gsub(/\s\w+$/,'...')
"This is some text it is really "

>> desc[0..30].gsub(/\s\w+\s*$/,'...')
"This is some text it is..."

Answer 3

@ evfwcqcg的答案非常好.我发现它什么时候效果不好

1. 该字符串包含非空格而非字母数字的其他字符.
2. 字符串短于所需长度.

示范:

>> s = "How about we put some ruby method Class#Method in our string"
=> "How about we put some ruby method Class#Method in our string"
>> s[0..41].gsub(/\s\w+\s*$/, '...')
=> "How about we put some ruby method Class#Me"
>> s[0..999].gsub(/\s\w+\s*$/, '...')
=> "How about we put some ruby method Class#Method in our..."

这不是我的预期.

这是我用来解决这个问题的方法:

def truncate s, length = 30, ellipsis = '...'
  if s.length > length
    s.to_s[0..length].gsub(/[^\w]\w+\s*$/, ellipsis)
  else
    s
  end
end

在做测试时,输出如下:

>> s = "This is some text it is really long"
=> "This is some text it is really long"
>> truncate s
=> "This is some text it is..."

仍然按预期行事.

>> s = "How about we put some ruby method Class#Method in our string"
=> "How about we put some ruby method Class#Method in our string"
>> truncate s, 41
=> "How about we put some ruby method Class..."
>> truncate s, 999
=> "How about we put some ruby method Class#Method in our string"

这是更喜欢它.