元编程:如何发现对象的真实类? [英] Metaprogramming: How to discover the real class of an object?
问题描述
我在开玩笑Ruby中的元编程,我做了这段代码:
I was kidding with metaprogramming in Ruby and I did this code:
class Class
def ===(other)
other.kind_of?(self)
end
end
class FakeClass
def initialize(object)
methods.each {|m| eval "undef #{m}" if m.to_sym != :methods }
define = proc do |m|
eval(<<-END)
def #{m}(*a, &b)
@object.#{m}(*a, &b)
rescue Object
raise $!.class, $!.message.gsub("FakeClass", @object.class.to_s),
$!.backtrace-[$!.backtrace[-caller.size-1]]
end
END
end
object.methods.each {|m| define[m] }
def method_missing(name, *a, &b)
if @object.methods.include?(name.to_s)
define[name]
eval "@object.#{name}(*a, &b)"
elsif @object.methods.include?("method_missing")
eval "@object.#{name}(*a, &b)"
else
super
end
rescue Object
raise $!.class, $!.message.gsub("FakeClass", @object.class.to_s),
$!.backtrace-[$!.backtrace[-caller.size-1]]
end
@object = object
end
end
这将创建一个模仿对象的伪类.看:
This creates a fake class that mimics a object. Look:
a = FakeClass.new(1) # => 1
a.class # => Fixnum
a.methods # => Return all Fixnum methods
a + 1 # => 2 (is not a FakeClass)
Fixnum === a # => true
a.something # => NoMethodError:
# undefined method `something' for 1:Fixnum
class Fixnum
def foo
true
end
end
a.foo # => true
问题是,现在我不知道如何知道一个物体是真实的还是假的.换句话说,如果#class
返回对象的真实类.存在一些纯粹的红宝石方式来区分吗?
The problem is, now I don't know how to know if a object is real or fake. In others words, if #class
returns the true class of the object. Exist some pure ruby way to differentiate?
在我不知道FakeClass存在或我不知道FakeClass的名称的情况下思考.这意味着我无法编辑FakeClass来添加类似#is_fake?
的方法.
Think in a scenario where I don't know that FakeClass exist or I don't know what is the name of the FakeClass. It means I can't edit the FakeClass to add a method like #is_fake?
.
PS:我知道a.instance_eval {self}
返回对象(不是伪造的).但是,检查a
是否为伪造并没有帮助.
PS: I know that a.instance_eval {self}
returns the object (not fake). But it doesn't help to check if a
is fake.
推荐答案
这是另一个答案:
a = FakeClass.new(1)
b = 1
da = Marshal.dump(a)
db = Marshal.dump(b)
puts da == db #=> false
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