Ruby: how to remove items from array A if it's not in array B?

Question

I have prepare these two arrays:

list_of_students = Student.where(\'class = ?\', param[:given_class])
list_of_teachers = Teacher.where(...)

Answer 1

You can try something like

a = [1,2,3]
b = [1,4,5]

pry(main)> a.delete_if {|a1| !b.include? a1}
=> [1]

it checks each value in a is in b or not. If not it deletes the value from a and gives you a array finally.

This is an example. You can use this accordingly