How can I delete one element from an array by value

Question

I have an array of elements in Ruby

[2,4,6,3,8]

I need to remove elements with value 3 for example

How do I do that?<

Answer 1

Non-destructive removal of first occurrence:

a = [2, 4, 6, 3, 8]
n = a.index 3
a.take(n)+a.drop(n+1)

Answer 2

I'm not sure if anyone has stated this, but Array.delete() and -= value will delete every instance of the value passed to it within the Array. In order to delete the first instance of the particular element you could do something like

arr = [1,3,2,44,5]
arr.delete_at(arr.index(44))

#=> [1,3,2,5]

There could be a simpler way. I'm not saying this is best practice, but it is something that should be recognized.

Answer 3

You can also monkey patch it. I never understood why Ruby has an except method for Hash but not for Array:

class Array
  def except value
    value = value.kind_of(Array) ? value : [value]
    self - value
  end
end

Now you can do:

[1,3,7,"436",354,nil].except(354) #=> [1,3,7,"436",nil]

Or:

[1,3,7,"436",354,nil].except([354, 1]) #=> [3,7,"436",nil]

Answer 4

So when you have multiple occurrences of 3 and you want only to delete the first occurrence of 3, you can simply do some thing as below.

arr = [2, 4, 6, 3, 8, 10, 3, 12]

arr.delete_at arr.index 3

#This will modify arr as [2, 4, 6, 8, 10, 3, 12] where first occurrence of 3 is deleted. Returns the element deleted. In this case => 3.

Answer 5

You can simply run:

[2,4,6,3,8].delete(3)

Answer 6

Assuming you want to delete 3 by value at multiple places in an array, I think the ruby way to do this task would be to use the delete_if method:

[2,4,6,3,8,3].delete_if {|x| x == 3 } 

You can also use delete_if in removing elements in the scenario of 'array of arrays'.

Hope this resolves your query