StrongParameters で配列の中身のパラメータチェック ref: http://qiita.com/yutackall/items/51eabf95b2dbdbe71897

file0.rb

params.permit(:users => [])

file0.txt

params.permit(:users => [])

file1.txt

{
  "users": [
    { "role": "admin", "name": "taro" },
    { "role": "user", "name": "hanako" },
    { "role": "user", "name": "jiro" },
    { "role": "user", "name": "saburo" },
  ]
}

file2.txt

console » users = {
        »   users: [
        »     { role: 'admin', name: 'taro' },
        »     { role: 'user', name: 'hanako' },
        »     { role: 'user', name: 'jiro' },
        »     { role: 'user', name: 'saburo' },
        »   ]
        » }

console » parameters = ActionController::Parameters.new(users)
console » parameters.require(:users).map { |u| u.permit(:role, :name) }
=> [
  [0] {
    "role" => "admin",
    "name" => "taro"
  },
  [1] {
    "role" => "user",
    "name" => "hanako"
  },
  [2] {
    "role" => "user",
    "name" => "jiro"
  },
  [3] {
    "role" => "user",
    "name" => "saburo"
  }
]

file3.txt

console » parameters.require(:users).map { |u| u.permit(:role) }
=> [
  [0] {
    "role" => "admin"
  },
  [1] {
    "role" => "user"
  },
  [2] {
    "role" => "user"
  },
  [3] {
    "role" => "user"
  }

file4.rb

private
def users_params
  params.require(:users).map { |u| u.permit(:role, :name) }
end

file4.txt

private
def users_params
  params.require(:users).map { |u| u.permit(:role, :name) }
end

file5.rb

User.create(users_params)

file5.txt

User.create(users_params)