strong_params_ambiguity.rb

# example from the documentation
# ==============================
params = ActionController::Parameters.new({
  person: {
    name: 'Francesco',
    age:  22,
    pets: [{
      name: 'Purplish',
      category: 'dogs'
    }]
  }
})

permitted = params.permit(person: [ :name, { pets: :name } ])
permitted.permitted?                    # => true
permitted[:person][:name]               # => "Francesco"
permitted[:person][:age]                # => nil
permitted[:person][:pets][0][:name]     # => "Purplish"
permitted[:person][:pets][0][:category] # => nil


# but look, pets doesn't have to be an array
# a hash will also work
# ==========================================
params = ActionController::Parameters.new({
  person: {
    name: 'Francesco',
    age:  22,
    pets: {
      name: 'Purplish',
      category: 'dogs'
    }
  }
})

permitted = params.permit(person: [ :name, { pets: :name } ])
permitted.permitted?                    # => true
permitted[:person][:name]               # => "Francesco"
permitted[:person][:age]                # => nil
permitted[:person][:pets][:name]     # => "Purplish"
permitted[:person][:pets][:category] # => nil


# I wonder if person has to be a hash?
# Nope
# ====================================
ActionController::Parameters.new({
  person: [{
    name: 'Francesco',
    age:  22,
    pets: [{
      name: 'Purplish',
      category: 'dogs'
    }]
  }]
})


permitted = params.permit(person: [ :name, { pets: :name } ])
permitted.permitted?                    # => true
permitted[:person][0][:name]               # => "Francesco"
permitted[:person][0][:age]                # => nil
permitted[:person][0][:pets][0][:name]     # => "Purplish"
permitted[:person][0][:pets][0][:category] # => nil