I would like to create a new array by inserting a new element to an existing array. But I do not want to mutate the existing array. I want:
A = [1, 2, 3]
to remains as is, while creating:
B = [1, 2, 3, 4]
Any suggestions?
This code:
B = A << 4
results in:
B = [1, 2, 3, 4]
A = [1, 2, 3, 4]
Do
B = A + [4]
or
B = [*A, 4]
or
B = A.dup << 4
B is a newly created one, and A indeed points to the same object as before. If you are mentioning the necessity to deep duplicate, then that is a valid note.B = Marshal.load(Marshal.dump A) (why are you using constants here btw?) Another way, slightly cleaner and more obvious is to implement deep_dup methods. You can steal it from ActiveSupport: api.rubyonrails.org/files/activesupport/lib/active_support/…when you assign one array it just copies the reference and both of them point to the same reference. so a change in one is reflected when you print either of them.
orig_array = [1,2,3,4]<br>
another_array = orig_array
puts orig_array.unshift(0).inspect
puts another_array.inspect
[0, 1, 2, 3, 4]
[0, 1, 2, 3, 4]
To avoid this you can use Marshal to copy from original array without impacting the object to which it is copied. Any changes in the original array will not change the object to which it is copied.
orig_array = [1,2,3,4]<br>
another_array = Marshal.load(Marshal.dump(orig_array))
puts orig_array.unshift(0).inspect
puts another_array.inspect
[0, 1, 2, 3, 4]
[1, 2, 3, 4]
I have already pasted this answer in another thread. Change value of a cloned object
