Don't use params objects inside methods other than your controller action methods in web frameworks

membership_controller_good_vs_bad.rb

################### BAD ########################

class MembershipsControllerBad < ApplicationController

  def create # the actual controller action
    ...
    ...
    create_invite(@org, current_user, email, existing_user)
    ...
    ...
  end
  
  private

  def create_invite(org, invitor, email, existing_user = nil)
    ...
    ...
    # The internals of this method should know nothing about params object. It's job is to handle the creation of invitation and
    # membership which is problem for another time. The action's purpose in life is specifically to be the bridge between the
    # request and it's format and the business logic, not just pass that job on.
    invite = Invitation.create!(email: email, organization_id: params[:membership][:organization_id])
    Membership.create!(user_id: user_id, organization_id: params[:membership][:organization_id], role: params[:membership][:role], pending: true, invitation_id: invite.id)
    ...
    ...
  end
  
end

############## BETTER ############################

class MembershipsControllerGood < ApplicationController

  def create # the actual controller action
    ...
    ...
    create_invite(@org, current_user, email, params[:membership][:role], existing_user)
    ...
    ...
  end
  
  private

  # Note: There are lots of other things that should be improved about this method in my opinion. But, in terms of the specific
  # topic this is the minimal change to make that improve without going down the rabbit hole of other impronvements.
  def create_invite(org, invitor, email, role, existing_user = nil)
    ...
    ...
    invite = Invitation.create!(email: email, organization_id: org.id)
    Membership.create!(user_id: user_id, organization_id: org.id, role: role, pending: true, invitation_id: invite.id)
    ...
    ...
  end
  
end