How to remove all elements that satisfy a condition in array in Ruby?

Question

How can I implement this in Ruby? Is there any one line of code technique? Let\'s say I want to get rid of all the elements which are less than 3 of an integer array.

Answer 1

You can use either new_array = array.reject {|x| x < 3} (reject returns a new array) or array.reject! {|x| x < 3} (reject! aka delete_if modifies the array in place).

There's also the (somewhat more common) select method, which acts like reject except that you specify the condition to keep elements, not to reject them (i.e. to get rid of the elements less than 3, you'd use new_array = array.select {|x| x >= 3}).

Answer 2

  a = [ "a", "b", "c" ]
  a.delete_if {|x| x >= "b" }   #=> ["a"]

Answer 3

Probably worth pointing out that

array.reject! {|x| x < 3}

and

array.delete_if {|x| x < 3}

Are the same, but

array.reject {|x| x < 3}

Will still return the same result, but not change the "array".

Answer 4

This works fine for numbers and letters in alphabetical order. their values are compared, what if the conditions change?

array = ["Type", ": Jointed", "Axes", ": 6", "Reach", ": 951 mm", "Capacity", ": 6 Kg", "Uses", ": ", "Arc welding, material handling, machine loading, application", "This particular unit is in excellent condition with under 700 hours."]

We need to delete all elemetns after the "Uses" value example:

array = ["Type", ": Jointed", "Axes", ": 6", "Reach", ": 951 mm", "Capacity", ": 6 Kg"]

So, that desition is not working (it just remove one element):

array.delete_if {|x| x >= "Uses" }
["Type", ": Jointed", "Axes", ": 6", "Reach", ": 951 mm", "Capacity", ": 6 Kg", ": ", "Arc welding, material handling, machine loading, application", "This particular unit is in excellent condition with under 700 hours."]