Adding dynamic views to a UIScrollView

Question

So I'm trying to clone the Apple weather app. My ViewHierarchy looks like this:

ViewControllerA contains a UIScrollView which in turn contains a UIView (UIView1) and the UIView contains child elements.There is also a button below the UIScrollView to add more UIView inside the UIScrollView . This UIViewController is designed in IB using AutoLayout .

When I click this button ideally I want to clone the UIView1 and add it to the UIScrollView , to the righthandside end of the currentView inside the UIScrollView . This is a horizontal scroll function. This is where I am stuck.

What I have tried are the following: Create a copy of UIView1 in a xib and load that. Create a UIView programmatically and load that.

In both the cases I'm facing the auto layout constraints issue. When I load the second view, it's overwritten on top of the existing view. I can hardcode the frame sizes for the cloned UIView and get it to work but obviously that won't work across devices.

So I'm adding constraints - something like this:

func buildView(startX:CGFloat, model:CityModel) -> UIView {
    var frame:CGRect = CGRectMake(0, 0, insideScrollView.bounds.width,     insideScrollView.bounds.height)
    var cityView:UIView = UIView(frame: frame)
    var lFrame:CGRect = CGRectMake(0, 0, 100,50)
    var cLabel:UILabel = UILabel(frame: lFrame)
    cLabel.text = model.name
    cLabel.sizeToFit()
    cLabel.textAlignment = .Center

    //cityView.addSubview(cLabel)
    cityView.layer.backgroundColor = UIColor.blueColor().CGColor
    cityView.setTranslatesAutoresizingMaskIntoConstraints(false)

    var constX = NSLayoutConstraint(item: cityView, attribute: NSLayoutAttribute.LeftMargin, relatedBy: NSLayoutRelation.Equal, toItem: cityScrollView, attribute: NSLayoutAttribute.LeftMargin, multiplier: 1, constant: 0)

    cityView.addConstraint(constX)
    return cityView

}

The app crashes unable to load this constraint indicating that the view hierarchy does not support this constraint as all the views are not loaded.

I'll keep digging on how to resolve this but any help will be greatly appreciated. Here's my viewDidLoad method. Cities is an array of models containing the view data

override func viewDidLoad() {
    super.viewDidLoad()
    var startScroll = insideScrollView.bounds.width
    if cities != nil {
        for model in cities.cityModels {
            if model.selected {
                cityScrollView.addSubview(buildView(startScroll, model: model))
                startScroll += cityScrollView.bounds.width
            }

        }
    } else {
        var cityModel: CityModel = CityModel(name: "default")
        cityModel.selected = false
        cities = SearchCityModels.sharedInstance
        cities.cityModels.append(cityModel)

    }

}

Answer 1

Posting the answer on behalf of @k6sandeep. I had not loaded the view inside the scrollview but was adding constraints to it. So fixed the same by adding constraints after the insideview was loaded.