我正在使用Ruby on Rails 3.2.9和Ruby 1.9.3。给定一个字符串，我想删除该字符串末尾的所有 /字符。也就是说，例如：
From "abc/" to "abc"
From "abc//" to "abc"
From "abc///" to "abc"
...
From "a/b/c///" to "a/b/c"
我怎样才能做到（可能是使用正则表达式）？
我试过了：
string = string[0,string.length-1] if string.end_with?('/')
但它仅适用于一个角色。
答案 0 :(得分：5)
"abc//".sub %r{/+$}, ''
这只会删除字符串末尾的/。
我使用%r{}制作正则表达式，因为在这种情况下我不必转义/。
答案 1 :(得分：2)
有些基准是有序的。
因为Perry Horwich的回答与Huluk的答案基本相同，所以我认为他们的结果会相同。嘿，我错了。在查看它并意识到它正在进行字符串搜索而不是正则表达式之后，我修复了它并添加了固定测试。
在那之后，我做了一些摆弄，看看我能想出什么。我的解决方案似乎并不像其他解决方案那么简单，但是第一个解决方案对于短字符串同样快速地完成工作，在长字符串上可能会快一点。在处理短弦或长弦时，后两者是冲洗，但两者都非常快。我恢复了老式的技术，并且做了他们如何在“回到白天”的汇编程序中做到这一点。
require 'benchmark'
n = 1_000_000
def huluk(s)
s.sub %r{/+$}, ''
end
def apneadiving1(your_string)
matches = your_string.match(/(.*?)\/*$/)
matches[1]
end
def apneadiving2(your_string)
your_string.scan(/(.*?)\/*$/).flatten.first
end
def fixed_perry_horwich(my_beginning_string)
my_beginning_string.sub(/\/+$/,'')
end
def the_tin_man1(s)
s.split(%r[/+$]).first
end
def the_tin_man2(s)
s = s[0..-2] while s[-1] == '/'
s
end
def the_tin_man3(s)
s_len = s.length - 1
s_len -= 1 while s[s_len] == '/'
s[0..s_len]
end
puts "Ruby #{ RUBY_VERSION }"
puts "#{ n } iterations"
puts
[
'abc//',
'abc' * 50 + '//',
'abc' * 10 + '////',
'////////////'
].each do |sample_string|
puts "sample string: #{ sample_string }"
puts 'huluk: %s' % huluk(sample_string)
puts 'perry_horwich: %s' % perry_horwich(sample_string)
puts 'fixed_perry_horwich: %s' % fixed_perry_horwich(sample_string)
puts 'apneadiving1: %s' % apneadiving1(sample_string)
puts 'apneadiving2: %s' % apneadiving2(sample_string)
puts 'the_tin_man1: %s' % the_tin_man1(sample_string)
puts 'the_tin_man2: %s' % the_tin_man2(sample_string)
puts 'the_tin_man3: %s' % the_tin_man3(sample_string)
puts
Benchmark.bm(19) do |b|
2.times do
b.report('huluk') { n.times { huluk(sample_string) } }
b.report('fixed_perry_horwich') { n.times { fixed_perry_horwich(sample_string) } }
b.report('apneadiving1') { n.times { apneadiving1(sample_string) } }
b.report('apneadiving2') { n.times { apneadiving2(sample_string) } }
b.report('the_tin_man1') { n.times { the_tin_man1(sample_string) } }
b.report('the_tin_man2') { n.times { the_tin_man2(sample_string) } }
b.report('the_tin_man3') { n.times { the_tin_man3(sample_string) } }
puts
end
end
puts
end
结果：
Ruby 1.9.3 1000000 iterations
sample string: abc//
huluk: abc
perry_horwich: abc//
fixed_perry_horwich: abc
apneadiving1: abc
apneadiving2: abc
the_tin_man1: abc
the_tin_man2: abc
the_tin_man3: abc
user system total real
huluk 1.840000 0.000000 1.840000 ( 1.849929)
fixed_perry_horwich 1.840000 0.010000 1.850000 ( 1.847069)
apneadiving1 1.900000 0.010000 1.910000 ( 1.900817)
apneadiving2 4.860000 0.010000 4.870000 ( 4.883103)
the_tin_man1 1.830000 0.000000 1.830000 ( 1.826547)
the_tin_man2 1.150000 0.000000 1.150000 ( 1.151420)
the_tin_man3 1.170000 0.010000 1.180000 ( 1.168161)
huluk 1.820000 0.000000 1.820000 ( 1.825440)
fixed_perry_horwich 1.830000 0.000000 1.830000 ( 1.827306)
apneadiving1 1.850000 0.000000 1.850000 ( 1.853751)
apneadiving2 4.830000 0.000000 4.830000 ( 4.825394)
the_tin_man1 1.810000 0.000000 1.810000 ( 1.811503)
the_tin_man2 1.150000 0.000000 1.150000 ( 1.151865)
the_tin_man3 1.170000 0.000000 1.170000 ( 1.172259)
sample string: abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabc//
huluk: abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabc
perry_horwich: abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabc//
fixed_perry_horwich: abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabc
apneadiving1: abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabc
apneadiving2: abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabc
the_tin_man1: abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabc
the_tin_man2: abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabc
the_tin_man3: abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabc
user system total real
huluk 2.120000 0.000000 2.120000 ( 2.122156)
fixed_perry_horwich 2.130000 0.010000 2.140000 ( 2.136665)
apneadiving1 9.630000 0.030000 9.660000 ( 9.656817)
apneadiving2 12.420000 0.030000 12.450000 ( 12.459432)
the_tin_man1 2.080000 0.010000 2.090000 ( 2.090112)
the_tin_man2 1.570000 0.010000 1.580000 ( 1.573887)
the_tin_man3 1.380000 0.000000 1.380000 ( 1.388120)
huluk 2.130000 0.010000 2.140000 ( 2.134414)
fixed_perry_horwich 2.120000 0.010000 2.130000 ( 2.129399)
apneadiving1 9.620000 0.020000 9.640000 ( 9.646624)
apneadiving2 12.410000 0.020000 12.430000 ( 12.423327)
the_tin_man1 2.080000 0.010000 2.090000 ( 2.090938)
the_tin_man2 1.580000 0.010000 1.590000 ( 1.581131)
the_tin_man3 1.390000 0.000000 1.390000 ( 1.400093)
sample string: abcabcabcabcabcabcabcabcabcabc////
huluk: abcabcabcabcabcabcabcabcabcabc
perry_horwich: abcabcabcabcabcabcabcabcabcabc////
fixed_perry_horwich: abcabcabcabcabcabcabcabcabcabc
apneadiving1: abcabcabcabcabcabcabcabcabcabc
apneadiving2: abcabcabcabcabcabcabcabcabcabc
the_tin_man1: abcabcabcabcabcabcabcabcabcabc
the_tin_man2: abcabcabcabcabcabcabcabcabcabc
the_tin_man3: abcabcabcabcabcabcabcabcabcabc
user system total real
huluk 1.980000 0.010000 1.990000 ( 1.983149)
fixed_perry_horwich 1.970000 0.010000 1.980000 ( 1.979796)
apneadiving1 3.500000 0.010000 3.510000 ( 3.513885)
apneadiving2 6.320000 0.020000 6.340000 ( 6.348327)
the_tin_man1 2.070000 0.010000 2.080000 ( 2.075045)
the_tin_man2 2.800000 0.000000 2.800000 ( 2.801136)
the_tin_man3 1.840000 0.010000 1.850000 ( 1.851506)
huluk 1.980000 0.010000 1.990000 ( 1.980867)
fixed_perry_horwich 1.980000 0.010000 1.990000 ( 1.984776)
apneadiving1 3.510000 0.010000 3.520000 ( 3.523383)
apneadiving2 6.340000 0.020000 6.360000 ( 6.357442)
the_tin_man1 2.070000 0.000000 2.070000 ( 2.074559)
the_tin_man2 2.800000 0.010000 2.810000 ( 2.814275)
the_tin_man3 1.850000 0.010000 1.860000 ( 1.855621)
sample string: ////////////
huluk:
perry_horwich: ////////////
fixed_perry_horwich:
apneadiving1:
apneadiving2:
the_tin_man1:
the_tin_man2:
the_tin_man3:
user system total real
huluk 1.980000 0.010000 1.990000 ( 1.982700)
fixed_perry_horwich 1.980000 0.010000 1.990000 ( 1.984354)
apneadiving1 1.860000 0.000000 1.860000 ( 1.869155)
apneadiving2 4.840000 0.020000 4.860000 ( 4.852445)
the_tin_man1 2.010000 0.000000 2.010000 ( 2.020292)
the_tin_man2 5.060000 0.020000 5.080000 ( 5.070202)
the_tin_man3 6.390000 0.020000 6.410000 ( 6.412697)
huluk 1.980000 0.010000 1.990000 ( 1.987652)
fixed_perry_horwich 1.980000 0.010000 1.990000 ( 1.981360)
apneadiving1 1.860000 0.000000 1.860000 ( 1.871577)
apneadiving2 4.850000 0.020000 4.870000 ( 4.857329)
the_tin_man1 2.010000 0.010000 2.020000 ( 2.023877)
the_tin_man2 5.060000 0.010000 5.070000 ( 5.067753)
the_tin_man3 6.410000 0.020000 6.430000 ( 6.434523)
我试图将"abc//"的简单案例和我认为是152个字符的“恶化案例”括起来，以对抗所提出的模式和算法。
huluk和fixed_perry_horwich是更快的，因为它们之间的差异被编译掉，因为Ruby会解释源。
编辑：
一些改变：
perry_horwich测试，因为测试它没有任何意义。'////////////'的测试。它显示了剥离分隔符的最坏情况测试的结果。测试结果的结果是查看正在测试的数据类型，并选择最适合输入的算法。对某些输入有效的方法并不一定适用于其他输入。我发现有趣的是，“老派”方法使用正则表达式来缩短尾随分隔符字符串。我认为这是Ruby设置对编译代码的调用的结果。一旦分隔符字符串变长，编译后的代码就会有优势。
答案 2 :(得分：1)
使用正则表达式检索字符串的预期部分：
/(.*?)\/*$/
见Rubular。
reg = /(.*?)\/*$/
matches = your_string.match(reg)
result = matches[1]
#or
result = your_string.scan(reg).flatten.first
答案 3 :(得分：0)
这适用于您的示例：
my_no_slash_terminated_string = my_beginning_string.sub(/\/+$/,'')
考虑是否要在字符串末尾或附近考虑空格。