如何删除Rubymotion中的所有子视图？

Question

Basically, I have a quiz app where I add have questions, then switch to a different screen to show an expanded version of the correct answer after it is chosen. I've tried adding button and labels, but when I do this, I eventually end up with buttons and labels 'ghosting' on the screen, after I went them gone. How can I remove all subviews, so that each button and label I add from within a method appears on a fresh screen?

class MyApplicationController < UIViewController

def loadView  
    self.view = UIImageView.alloc.init  
end

def viewDidLoad  
    super  
    view.userInteractionEnabled=true  
    @question_index=0  
    @answerChoices = []  
    @questionChoices=["What is best in life?",...]  
    makeQuestion  
end  

def makeQuestion 
    left =20  
    top=100  
    label = UILabel.new  
    label.text =@questionChoices[@question_index]  
    label.textAlignment = UITextAlignmentCenter  
    label.textColor = UIColor.redColor  
    label.frame = [[20,20], [view.frame.size.width-40, 40]]  
    label.lineBreakMode = UILineBreakModeWordWrap  
    label.numberOfLines = 0  
    label.sizeToFit  
    view.image = UIImage.imageNamed('background.jpg')  
    view.addSubview(label)  
    4.times do |i|  
        @button = UIButton.buttonWithType(UIButtonTypeRoundedRect)  
    @button.setTitle(@answerChoices[i][@question_index], forState:UIControlStateNormal)  
        @button.frame = [[left, top], [view.frame.size.width - left * 2, 40]]  
    @button.addTarget(self, action:'actionTapped:', forControlEvents:UIControlEventTouchUpInside)  
        @button.tag=i  
        top+=45  
        view.addSubview(@button)  
    end  
end

def makeAnswer  
    @button.removeFromSuperview
    @button.removeFromSuperview
    @button.removeFromSuperview
    @button.removeFromSuperview
    view.image = UIImage.imageNamed('back.jpg')
    label = UILabel.new
    label.text =@rightArray[@question_index]
    label.textAlignment = UITextAlignmentCenter
    label.textColor = UIColor.blackColor
    label.frame = [[20,20], [view.frame.size.width-40, 40]]  
    label.lineBreakMode = UILineBreakModeWordWrap  
    label.numberOfLines = 0  
    label.sizeToFit  
    view.addSubview(label)  


    @button = UIButton.buttonWithType(UIButtonTypeRoundedRect)  
    @button.setTitle("More questions", forState:UIControlStateNormal)  
    @button.tag=1  
    @button.addTarget(self, action:'makeQuestion', forControlEvents:UIControlEventTouchUpInside)     
    @button.frame = [[20, 100], [view.frame.size.width - 20 * 2, 40]]  
    view.addSubview(@button)  
end 

end

Answer 1

You need an array of buttons. In your 4.times loop, you are overwriting the instance variable @button four times. Instead, make @button an array of buttons, and assign a different button to each index.

If you have a variable myView and want to remove all of its subviews, I believe this will work:

myView.subviews.each {|sv| sv.removeFromSuperview}