一般来说,与Struct相比,使用OpenStruct的优点和缺点是什么?什么样类型的通用用例适合每一个?
当前回答
结构:
>> s = Struct.new(:a, :b).new(1, 2)
=> #<struct a=1, b=2>
>> s.a
=> 1
>> s.b
=> 2
>> s.c
NoMethodError: undefined method `c` for #<struct a=1, b=2>
OpenStruct:
>> require 'ostruct'
=> true
>> os = OpenStruct.new(a: 1, b: 2)
=> #<OpenStruct a=1, b=2>
>> os.a
=> 1
>> os.b
=> 2
>> os.c
=> nil
其他回答
看一下与新方法相关的API。这里有很多不同之处。
就我个人而言,我非常喜欢OpenStruct,因为我不需要预先定义对象的结构,只需要添加我想要的东西。我猜这将是它的主要(缺点)优势?
http://www.ruby-doc.org/core/classes/Struct.html http://www.ruby-doc.org/stdlib/libdoc/ostruct/rdoc/classes/OpenStruct.html
使用OpenStruct,您可以任意创建属性。另一方面,Struct必须在创建时定义其属性。选择一种还是另一种应该主要基于您以后是否需要能够添加属性。
The way to think about them is as the middle ground of the spectrum between Hashes on one side and classes on the other. They imply a more concrete relationship amongst the data than does a Hash, but they don't have the instance methods as would a class. A bunch of options for a function, for example, make sense in a hash; they're only loosely related. A name, email, and phone number needed by a function could be packaged together in a Struct or OpenStruct. If that name, email, and phone number needed methods to provide the name in both "First Last" and "Last, First" formats, then you should create a class to handle it.
结构:
>> s = Struct.new(:a, :b).new(1, 2)
=> #<struct a=1, b=2>
>> s.a
=> 1
>> s.b
=> 2
>> s.c
NoMethodError: undefined method `c` for #<struct a=1, b=2>
OpenStruct:
>> require 'ostruct'
=> true
>> os = OpenStruct.new(a: 1, b: 2)
=> #<OpenStruct a=1, b=2>
>> os.a
=> 1
>> os.b
=> 2
>> os.c
=> nil
与Structs相比,OpenStructs使用的内存明显更多,运行速度更慢。
require 'ostruct'
collection = (1..100000).collect do |index|
OpenStruct.new(:name => "User", :age => 21)
end
在我的系统上,以下代码在14秒内执行,消耗了1.5 GB内存。你的里程可能有所不同:
User = Struct.new(:name, :age)
collection = (1..100000).collect do |index|
User.new("User",21)
end
这几乎是在瞬间完成的,消耗了26.6 MB的内存。
其他指标:
require 'benchmark'
require 'ostruct'
REP = 100000
User = Struct.new(:name, :age)
USER = "User".freeze
AGE = 21
HASH = {:name => USER, :age => AGE}.freeze
Benchmark.bm 20 do |x|
x.report 'OpenStruct slow' do
REP.times do |index|
OpenStruct.new(:name => "User", :age => 21)
end
end
x.report 'OpenStruct fast' do
REP.times do |index|
OpenStruct.new(HASH)
end
end
x.report 'Struct slow' do
REP.times do |index|
User.new("User", 21)
end
end
x.report 'Struct fast' do
REP.times do |index|
User.new(USER, AGE)
end
end
end
对于那些没有耐心的人来说,他们想要了解基准测试结果,而不需要自己运行它们,下面是上面代码的输出(在MB Pro 2.4GHz i7上)
user system total real
OpenStruct slow 4.430000 0.250000 4.680000 ( 4.683851)
OpenStruct fast 4.380000 0.270000 4.650000 ( 4.649809)
Struct slow 0.090000 0.000000 0.090000 ( 0.094136)
Struct fast 0.080000 0.000000 0.080000 ( 0.078940)
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