ruby - ruby 中#entries 和#to_a 的区别

Question

#entries 之间的基本区别是什么？和 #to_a Enumerable 的方法ruby 中的模块。两者似乎在 Hash 上返回相同的结果

>> hash = {"name" => "foo" , "age" => "23"}
=> {"name"=>"foo", "age"=>"23"}

>> hash.to_a 
=> [["name","foo"],["age",23]]

>> hash.entries
=> [["name","foo"],["age",23]]

Answer 1

这是区别(查看 # => 之后的输出):

h = {}
h.method(:entries) # => #<Method: Hash(Enumerable)#entries>
h.method(:to_a) # => #<Method: Hash#to_a>
h.method(:entries).owner # => Enumerable
h.method(:to_a).owner # => Hash

Hash 有一个实例方法 #to_a , 所以它没有调用 Enumerable#to_a .但是 Hash 没有它自己的方法 #entries，所以它调用 Enumerable#entries , 因为 Hash 包含了 Enumerable 模块。

Hash.included_modules # => [Enumerable, Kernel]

Enumerable#entries 和 Enumerable#to_a 之间没有区别，据我所知，两者使用 TracePoint 的工作方式相似:

1. trace = TracePoint.new do |tp|
2.    p [tp.lineno, tp.event, tp.defined_class,tp.method_id]
3. end
4.
5. trace.enable do
6.  (1..2).entries
7.  (1..2).to_a
8. end

# >> [5, :b_call, nil, nil]
# >> [6, :line, nil, nil]
# >> [6, :line, nil, nil]
# >> [6, :c_call, Enumerable, :entries]
# >> [6, :c_call, Range, :each]
# >> [6, :c_return, Range, :each]
# >> [6, :c_return, Enumerable, :entries]
# >> [7, :line, nil, nil]
# >> [7, :line, nil, nil]
# >> [7, :c_call, Enumerable, :to_a]
# >> [7, :c_call, Range, :each]
# >> [7, :c_return, Range, :each]
# >> [7, :c_return, Enumerable, :to_a]
# >> [8, :b_return, nil, nil]

是的，Hash#to_a 比 Enumerable#to_a 快。

第一部分

require 'benchmark'

class Hash
  remove_method :to_a
end

hsh = Hash[*1..1000]


Benchmark.bm(10) do |b|
  b.report("Enumerable#to_a")    { hsh.to_a }
end
# >>                  user     system      total        real
# >> Enumerable#to_a  0.000000   0.000000   0.000000 (  0.000126)

第二部分

require 'benchmark'

hsh = Hash[*1..1000]


Benchmark.bm(10) do |b|
  b.report("Hash#to_a")    { hsh.to_a }
end
# >>                  user     system      total        real
# >> Hash#to_a     0.000000   0.000000   0.000000 (  0.000095)