Why does String::sub!() change the original of a cloned object in Ruby?
I have a struct in my Ruby code that looks somewhat like this
Parameter = Struct.new(:name, :id, :default_value, :minimum, :maximum)
later, I create an instance of this struct using
freq = Parameter.new('frequency', 15, 1000.0, 20.0, 20000.0)
At some point, I need an exact duplicate of this struct开发者_开发技巧, so I call
newFreq = freq.clone
Then, I change newFreq
's name
newFreq.name.sub!('f', 'newF')
Which, miraculously, changes freq.name
, too!
A simple assignment like newFreq.name = 'newFrequency'
does not change freq
.
Is this the way this is supposed to work?
Edit: Is it a good idea to use a class instead of a struct and overload clone
to make a deep copy?
newFreq
is a shallow copy of freq
. That means that each of the references stored inside of newFreq
points to the object as the ones stored in freq
. You can change where the references point independantly (newFreq.name = newFreq.name.sub 'f','newF'
), but if you call a method that mutates the object, both newFreq
and freq
will be affected.
See also http://en.wikipedia.org/wiki/Object_copy
The Object#clone
method performs shallow copy. You need deep copy to get the job done.
Follow this link to learn about deep copy in Ruby.
精彩评论