How to randomize this QuestionBank

How do I randomize and make sure no questions repeat in this Question Bank?

var list = [Questions]()

init () {


    let item = Questions(text: " ", correctAnswer: " ", textA: " ", textB: " ", textC: " ", textD: " " )

    list.append(item)

    list.append(Questions(text: " ", correctAnswer: " ", textA: " ", textB: " ", textC: " ", textD: " "))