什么时候在Ruby中使用结构比使用哈希更好?

5 回复 | 直到 17 年前

1

22

gaqzi 17 年前

就我个人而言,当我想让一段数据像一个数据集合一样工作,而不是在一个框架下松散耦合时,我会使用struct Hash .


Video = Struct.new(:title, :video_id, :id) do
  def to_s
    "http://youtube.com/get_video.php?t=#{id}&video_id=#{video_id}&fmt=18"
  end

  def empty?
    @title.nil? and @video_id.nil? and @id.nil?
  end
end

稍后在我的代码中,我有一个循环,它遍历视频源HTML页面中的所有行,直到 empty?

我看到的另一个例子是 James Edward Gray IIs configuration class OpenStruct

#!/usr/bin/env ruby -wKU

require "ostruct"

module Config
  module_function

  def load_config_file(path)
    eval <<-END_CONFIG
    config = OpenStruct.new
    #{File.read(path)}
    config
    END_CONFIG
  end
end

# configuration_file.rb
config.db = File.join(ENV['HOME'], '.cool-program.db')
config.user = ENV['USER']

# Usage:
Config = Config.load_config('configuration_file.rb')
Config.db   # => /home/ba/.cool-program.db
Config.user # => ba
Config.non_existant # => Nil

两者的区别 Struct 和 OpenStruct Struct 只响应您设置的属性, 响应任何属性集-但没有值集的将返回 Nil

2

10

JDonner 16 年前

结构具有通过索引和名称在其元素中获取的功能:

irb(main):004:0> Person = Struct.new(:name, :age)
=> Person
irb(main):005:0> p = Person.new("fred", 26)
=> #
irb(main):006:0> p[0]
=> "fred"
irb(main):007:0> p[1]
=> 26
irb(main):008:0> p.name
=> "fred"
irb(main):009:0> p.age
=> 26

这有时很有用。

3

9

mpospelov 8 年前

对于那些喜欢IPS(每秒迭代次数)指标的人来说,以下是更具可读性的基准:

require 'benchmark/ips'
require 'ostruct'

MyStruct = Struct.new(:a)
Benchmark.ips do |x|
  x.report('hash') { a = { a: 1 }; a[:a] }
  x.report('struct') { a = MyStuct.new(1); a.a }
  x.report('ostruct') { a = OpenStruct.new(a: 1); a.a }

  x.compare!
end

结果:

Warming up --------------------------------------
                hash   147.162k i/100ms
              struct   171.949k i/100ms
             ostruct    21.086k i/100ms
Calculating -------------------------------------
                hash      2.608M (Â± 3.1%) i/s -     13.097M in   5.028022s
              struct      3.680M (Â± 1.8%) i/s -     18.399M in   5.001510s
             ostruct    239.108k (Â± 5.5%) i/s -      1.202M in   5.046817s

Comparison:
              struct:  3679772.2 i/s
                hash:  2607565.1 i/s - 1.41x  slower
             ostruct:   239108.4 i/s - 15.39x  slower

对于庞大的列表:

require 'benchmark/ips'
require 'ostruct'

MyStruct = Struct.new(:a, :b, :c, :d, :e, :f, :g, :h, :i, :j, :k, :l, :m, :n, :o, :p, :q, :r, :s, :t, :u, :v, :w, :x, :y, :z)

Benchmark.ips do |x|
  x.report('hash') do
    hash = { a: 1, b: 2, c: 3, d: 4, e: 5, f: 6, g: 7, h: 8, i: 9, j: 10, k: 11, l: 12, m: 13, n: 14, o: 15, p: 16, q: 17, r: 18, s: 19, t: 20, u: 21, v: 22, w: 23, x: 24, y: 25, z: 26 }
    hash[:a]; hash[:b]; hash[:c]; hash[:d]; hash[:e]; hash[:f]; hash[:g]; hash[:h]; hash[:i]; hash[:j]; hash[:k]; hash[:l]; hash[:m]; hash[:n]; hash[:o]; hash[:p]; hash[:q]; hash[:r]; hash[:s]; hash[:t]; hash[:u]; hash[:v]; hash[:w]; hash[:x]; hash[:y]; hash[:z]
  end

  x.report('struct') do
    struct = MyStruct.new(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
    struct.a;struct.b;struct.c;struct.d;struct.e;struct.f;struct.g;struct.h;struct.i;struct.j;struct.k;struct.l;struct.m;struct.n;struct.o;struct.p;struct.q;struct.r;struct.s;struct.t;struct.u;struct.v;struct.w;struct.x;struct.y;struct.z
  end

  x.report('ostruct') do
    ostruct = OpenStruct.new( a: 1, b: 2, c: 3, d: 4, e: 5, f: 6, g: 7, h: 8, i: 9, j: 10, k: 11, l: 12, m: 13, n: 14, o: 15, p: 16, q: 17, r: 18, s: 19, t: 20, u: 21, v: 22, w: 23, x: 24, y: 25, z: 26)
    ostruct.a;ostruct.b;ostruct.c;ostruct.d;ostruct.e;ostruct.f;ostruct.g;ostruct.h;ostruct.i;ostruct.j;ostruct.k;ostruct.l;ostruct.m;ostruct.n;ostruct.o;ostruct.p;ostruct.q;ostruct.r;ostruct.s;ostruct.t;ostruct.u;ostruct.v;ostruct.w;ostruct.x;ostruct.y;ostruct.z;
  end

  x.compare!
end

Warming up --------------------------------------
                hash    51.741k i/100ms
              struct    62.346k i/100ms
             ostruct     1.010k i/100ms
Calculating -------------------------------------
                hash    603.104k (Â± 3.9%) i/s -      3.053M in   5.070565s
              struct    780.005k (Â± 3.4%) i/s -      3.928M in   5.041571s
             ostruct     11.321k (Â± 3.4%) i/s -     56.560k in   5.001660s

Comparison:
              struct:   780004.8 i/s
                hash:   603103.8 i/s - 1.29x  slower
             ostruct:    11321.2 i/s - 68.90x  slower

结论

4

8

Community Mohan Dere 9 年前

主要是表演。Struct的速度要快得多,按数量级排列。与哈希或OpenStruct相比,它消耗的内存更少。更多信息请点击此处: When should I use Struct vs. OpenStruct?

5

6

the Tin Man 9 年前

关于使用Hash的速度,Struct或OpenStruct:Hash在一般情况下都会获得成功。它是OpenStruct的基础,没有额外的糖霜,所以它不是那么灵活,但它是精简和平均的。

使用Ruby 2.4.1:

require 'fruity'
require 'ostruct'

def _hash
  h = {}
  h['a'] = 1
  h['a']
end

def _struct
  s = Struct.new(:a)
  foo = s.new(1)
  foo.a
end

def _ostruct
  person = OpenStruct.new
  person.a = 1
  person.a
end

compare do
  a_hash { _hash }
  a_struct { _struct }
  an_ostruct { _ostruct }
end

# >> Running each test 4096 times. Test will take about 2 seconds.
# >> a_hash is faster than an_ostruct by 13x Â± 1.0
# >> an_ostruct is similar to a_struct

使用更简洁的哈希和OpenStruct定义:

require 'fruity'
require 'ostruct'

def _hash
  h = {'a' => 1}
  h['a']
end

def _struct
  s = Struct.new(:a)
  foo = s.new(1)
  foo.a
end

def _ostruct
  person = OpenStruct.new('a' => 1)
  person.a
end

compare do
  a_hash { _hash }
  a_struct { _struct }
  an_ostruct { _ostruct }
end

# >> Running each test 4096 times. Test will take about 2 seconds.
# >> a_hash is faster than an_ostruct by 17x Â± 10.0
# >> an_ostruct is similar to a_struct

require 'fruity'
require 'ostruct'

HSH = {'a' => 1}
def _hash
  HSH['a']
end

STRCT = Struct.new(:a).new(1)
def _struct
  STRCT.a
end

OSTRCT = OpenStruct.new('a' => 1)
def _ostruct
  OSTRCT.a
end

puts "Ruby version: #{RUBY_VERSION}"

compare do
  a_hash { _hash }
  a_struct { _struct }
  an_ostruct { _ostruct }
end

# >> Ruby version: 2.4.1
# >> Running each test 65536 times. Test will take about 2 seconds.
# >> a_struct is faster than a_hash by 4x Â± 1.0
# >> a_hash is similar to an_ostruct

但是请注意,对于访问,Struct只比Hash快4倍,而对于初始化、赋值和访问,Hash快17倍。您必须根据特定应用程序的需要确定哪种应用程序最适合使用。因此,我倾向于使用散列作为一般用途。

而且,使用OpenStruct的速度在过去几年中有了很大的提高;根据我过去看到的基准测试,与1.9.3-p551相比,它过去比Struct慢:

require 'fruity'
require 'ostruct'

def _hash
  h = {}
  h['a'] = 1
  h['a']
end

def _struct
  s = Struct.new(:a)
  foo = s.new(1)
  foo.a
end

def _ostruct
  person = OpenStruct.new
  person.a = 1
  person.a
end

puts "Ruby version: #{RUBY_VERSION}"

compare do
  a_hash { _hash }
  a_struct { _struct }
  an_ostruct { _ostruct }
end

# >> Ruby version: 1.9.3
# >> Running each test 4096 times. Test will take about 2 seconds.
# >> a_hash is faster than a_struct by 7x Â± 1.0
# >> a_struct is faster than an_ostruct by 2x Â± 0.1

以及:

require 'fruity'
require 'ostruct'

def _hash
  h = {'a' => 1}
  h['a']
end

def _struct
  s = Struct.new(:a)
  foo = s.new(1)
  foo.a
end

def _ostruct
  person = OpenStruct.new('a' => 1)
  person.a
end

puts "Ruby version: #{RUBY_VERSION}"

compare do
  a_hash { _hash }
  a_struct { _struct }
  an_ostruct { _ostruct }
end

# >> Ruby version: 1.9.3
# >> Running each test 4096 times. Test will take about 2 seconds.
# >> a_hash is faster than a_struct by 7x Â± 1.0
# >> a_struct is faster than an_ostruct by 2x Â± 1.0

以及:

require 'fruity'
require 'ostruct'

HSH = {'a' => 1}
def _hash
  HSH['a']
end

STRCT = Struct.new(:a).new(1)
def _struct
  STRCT.a
end

OSTRCT = OpenStruct.new('a' => 1)
def _ostruct
  OSTRCT.a
end

puts "Ruby version: #{RUBY_VERSION}"

compare do
  a_hash { _hash }
  a_struct { _struct }
  an_ostruct { _ostruct }
end

# >> Ruby version: 1.9.3
# >> Running each test 32768 times. Test will take about 1 second.
# >> a_struct is faster than an_ostruct by 3x Â± 1.0
# >> an_ostruct is similar to a_hash

6

1

ogirginc 5 年前

benchmarks 关于Ruby 3.0.0p0(2020-12-25修订版95aff21468)[x86_64-darwin20]。

Warming up --------------------------------------
                hash     1.008M i/100ms
              struct   423.906k i/100ms
             ostruct    16.384k i/100ms
Calculating -------------------------------------
                hash      9.923M (Â± 1.9%) i/s -     50.412M in   5.082029s
              struct      4.327M (Â± 2.6%) i/s -     22.043M in   5.097358s
             ostruct    158.771k (Â± 6.7%) i/s -    802.816k in   5.084066s

Comparison:
                hash:  9923144.6 i/s
              struct:  4327316.1 i/s - 2.29x  (Â± 0.00) slower
             ostruct:   158771.4 i/s - 62.50x  (Â± 0.00) slower

庞大的名单

Warming up --------------------------------------
                hash    71.378k i/100ms
              struct    99.245k i/100ms
             ostruct   855.000  i/100ms
Calculating -------------------------------------
                hash    712.113k (Â± 4.9%) i/s -      3.569M in   5.024094s
              struct      1.098M (Â± 2.9%) i/s -      5.558M in   5.066160s
             ostruct      8.629k (Â± 4.8%) i/s -     43.605k in   5.066147s

Comparison:
              struct:  1098071.6 i/s
                hash:   712112.5 i/s - 1.54x  (Â± 0.00) slower
             ostruct:     8628.8 i/s - 127.26x  (Â± 0.00) slower

结论

如果性能确实重要,请使用struct。