Ruby中的字符串连接

我正在寻找一种更优雅的方式来连接Ruby中的字符串.

我有以下几行:

source = "#{ROOT_DIR}/" << project << "/App.config"

这样做有更好的方法吗？

就此而言,<<和之间的区别是+什么？

您可以通过以下几种方式实现:

如你所示,<<但这不是通常的方式

使用字符串插值

source = "#{ROOT_DIR}/#{project}/App.config"

同 +

source = "#{ROOT_DIR}/" + project + "/App.config"

第二种方法在内存/速度方面似乎比我看到的更有效(虽然没有测量).当ROOT_DIR为零时,所有三种方法都会抛出未初始化的常量错误.

处理路径名时,您可能希望使用File.join以避免弄乱路径名分隔符.

最后,这是一个品味问题.

该+操作是正常级联选择,可能是连接字符串的最快方法.

+和之间的区别<<是<<改变左侧的对象,而+不是.

irb(main):001:0> s = 'a'
=> "a"
irb(main):002:0> s + 'b'
=> "ab"
irb(main):003:0> s
=> "a"
irb(main):004:0> s << 'b'
=> "ab"
irb(main):005:0> s
=> "ab"

如果您只是连接路径,则可以使用Ruby自己的File.join方法.

source = File.join(ROOT_DIR, project, 'App.config')

来自http://greyblake.com/blog/2012/09/02/ruby-perfomance-tricks/

使用<<aka concat远比使用aka 更有效+=,因为后者创建一个时态对象并用新对象覆盖第一个对象.

require 'benchmark'

N = 1000
BASIC_LENGTH = 10

5.times do |factor|
  length = BASIC_LENGTH * (10 ** factor)
  puts "_" * 60 + "\nLENGTH: #{length}"

  Benchmark.bm(10, '+= VS <<') do |x|
    concat_report = x.report("+=")  do
      str1 = ""
      str2 = "s" * length
      N.times { str1 += str2 }
    end

    modify_report = x.report("<<")  do
      str1 = "s"
      str2 = "s" * length
      N.times { str1 << str2 }
    end

    [concat_report / modify_report]
  end
end

输出:

____________________________________________________________
LENGTH: 10
                 user     system      total        real
+=           0.000000   0.000000   0.000000 (  0.004671)
<<           0.000000   0.000000   0.000000 (  0.000176)
+= VS <<          NaN        NaN        NaN ( 26.508796)
____________________________________________________________
LENGTH: 100
                 user     system      total        real
+=           0.020000   0.000000   0.020000 (  0.022995)
<<           0.000000   0.000000   0.000000 (  0.000226)
+= VS <<          Inf        NaN        NaN (101.845829)
____________________________________________________________
LENGTH: 1000
                 user     system      total        real
+=           0.270000   0.120000   0.390000 (  0.390888)
<<           0.000000   0.000000   0.000000 (  0.001730)
+= VS <<          Inf        Inf        NaN (225.920077)
____________________________________________________________
LENGTH: 10000
                 user     system      total        real
+=           3.660000   1.570000   5.230000 (  5.233861)
<<           0.000000   0.010000   0.010000 (  0.015099)
+= VS <<          Inf 157.000000        NaN (346.629692)
____________________________________________________________
LENGTH: 100000
                 user     system      total        real
+=          31.270000  16.990000  48.260000 ( 48.328511)
<<           0.050000   0.050000   0.100000 (  0.105993)
+= VS <<   625.400000 339.800000        NaN (455.961373)

由于这是一条路径,我可能会使用数组和连接:

source = [ROOT_DIR, project, 'App.config'] * '/'

这是另一个受这个要点启发的基准.它比较动态和预定义字符串的concatenation(+),appending(<<)和interpolation(#{}).

require 'benchmark'

# we will need the CAPTION and FORMAT constants:
include Benchmark

count = 100_000


puts "Dynamic strings"

Benchmark.benchmark(CAPTION, 7, FORMAT) do |bm|
  bm.report("concat") { count.times { 11.to_s +  '/' +  12.to_s } }
  bm.report("append") { count.times { 11.to_s << '/' << 12.to_s } }
  bm.report("interp") { count.times { "#{11}/#{12}" } }
end


puts "\nPredefined strings"

s11 = "11"
s12 = "12"
Benchmark.benchmark(CAPTION, 7, FORMAT) do |bm|
  bm.report("concat") { count.times { s11 +  '/' +  s12 } }
  bm.report("append") { count.times { s11 << '/' << s12 } }
  bm.report("interp") { count.times { "#{s11}/#{s12}"   } }
end

Dynamic strings
              user     system      total        real
concat    0.050000   0.000000   0.050000 (  0.047770)
append    0.040000   0.000000   0.040000 (  0.042724)
interp    0.050000   0.000000   0.050000 (  0.051736)

Predefined strings
              user     system      total        real
concat    0.030000   0.000000   0.030000 (  0.024888)
append    0.020000   0.000000   0.020000 (  0.023373)
interp    3.160000   0.160000   3.320000 (  3.311253)

require 'pathname' # pathname is in stdlib
Pathname(ROOT_DIR) + project + 'App.config'

"String1" + "String2"

"#{String1} #{String2}"

String1<

等等 ... 

        

10> Boris Stitni..：
连说你说？怎么样的#concat方法呢？

a = 'foo'
a.object_id #=> some number
a.concat 'bar' #=> foobar
a.object_id #=> same as before -- string a remains the same object


平心而论,concat是别名<<.

        
还有一种方法可以将其他人没有提到的字符串粘合在一起,这仅仅是并置:`"foo""bar"'baz"#=>"foobarabaz"`