method
deep_dup
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Ruby on Rails latest stable (v7.1.3.2)
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Class: Hash
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- What's this?
deep_dup()
public
Returns a deep copy of hash.
hash = { a: { b: 'b' } } dup = hash.deep_dup dup[:a][:c] = 'c' hash[:a][:c] # => nil dup[:a][:c] # => "c"
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danielglh -
August 25, 2014 - (v3.1.0 - v3.2.13)
astgtciv -
February 2, 2015
joels -
January 6, 2016
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1 thank
This method does not correctly dup arrays
Watch out because this method does not correctly dup arrays values.
The bug can be reproduced with the following code:
hash = { 'a' => [1,2,3,4] } dup = hash.deep_dup dup['a'].object_id == hash['a'].object_id # should return true
Rails 4 version does not have this issue because it is completely different implementation.
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0 thanks
Be careful with cycles
This simplistic implementation (unlike Marshal.load(Marshal.dump(object)) doesn’t handle cycles in objects.
a = {} b = {a: a} a[:b] = b a.deep_dup # SystemStackError: stack level too deep
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What about Marshal remote code execution risks?
Good suggestion about using Marshal to avoid cycles, astgtciv, but what about the security risks of doing that?
See http://ruby-doc.org/core-2.2.2/Marshal.html where it states:
By design, ::load can deserialize almost any class loaded into the Ruby process. In many cases this can lead to remote code execution if the Marshal data is loaded from an untrusted source. As a result, ::load is not suitable as a general purpose serialization format and you should never unmarshal user supplied input or other untrusted data. If you need to deserialize untrusted data, use JSON or another serialization format that is only able to load simple, ‘primitive’ types such as String, Array, Hash, etc. Never allow user input to specify arbitrary types to deserialize into.