There are Two Types of Software Design...

Changing view's type on the Storyboard

Suppose the design of your app changed, and now you need to replace the Table View with a Collection View keeping all the constraints along with views hierarchy.

Drop a new View Controller on the storyboard and put a Collection View inside. Rename it in the left panel (called Document Outline). Name it "The Replacement" so you will be able recognize it later. Now switch to the Source Code through the Open As.

Now the storyboard looks like XML markup. Find the Table View you need to replace, it will be scoped within the tableView tag.

Copy its id (example: id="8Oa-xL-ums"). It points to the view in constraints and outlets. Now find the new Collection View under the collectionView tag.

Copy everything including the enclosing tags: <collectionView ...</collectionView> and paste it instead of the tableView. Replace Collection View's id with the value you copied from the Table View. Before switching back to Interface Builder you need to clean up the storyboard. Remove the scene of the temporary View Controller that you created at the beginning of the tutorial. Delete everything between tags and the preceding comment: <!--View Controller><scene ...</scene>. If you don't do this you will have an error because of duplicated id.

Now you will have the new Collection View constrained like the Table View but misplaced, because it's was copied with the rect.

Click Update Frames and enjoy the result!

Here is the list of storyboard tags for different UI classes. Who knows, may be it will be useful.

arscnView	ARSCNView
arskView	ARSKView
glkView	GLKView
mapView	MKMapView
mtkView	MTKView
sceneKitView	SCNView
skView	SKView
activityIndicatorView	UIActivityIndicatorView
button	UIButton
collectionView	UICollectionView
datePicker	UIDatePicker
imageView	UIImageView
label	UILabel
navigationBar	UINavigationBar
pageControl	UIPageControl
pickerView	UIPickerView
progressView	UIProgressView
scrollView	UIScrollView
searchBar	UISearchBar
segmentedControl	UISegmentedControl
slider	UISlider
stackView	UIStackView
stepper	UIStepper
switch	UISwitch
tabBar	UITabBar
tableView	UITableView
textField	UITextField
textView	UITextView
toolbar	UIToolbar
view	UIView
containerView	UIView (with embedded View Controller)
visualEffectView	UIVisualEffectView
webView	UIWebView
wkWebView	WKWebView

Safer parsing with JSONSerialization in Swift

Github gist.

Most people use the following snippet to get a value from an object provided by the JSONSerialization:
guard let name = jsonDictionary["name"] as? String else { return } ...
It's not obvious, but this code is unsafe. It can easily fail if the "name" value will be "111". In this case it may be decoded as NSNumber and casting to String will always fail. The same thing with numbers:
guard let id = jsonDictionary["id"] as? Int else { return } // id can be a "3" String! ... A value like "3" can be decoded both as NSString and NSNumber (more often).

I didn't find any tutorial that would take this issue into account. All of them recommend to use as? to unknown JSON object to basic type. So I post here the correct snippets that will provide stable and predictable results in all possible cases.

JSON helpers

extension String { init?(jsonObject: Any?) { guard jsonObject is NSNull == false else { return nil } let aNSObject = jsonObject as? NSObject if let description = aNSObject?.description { self = description } else { return nil } } } extension Int { var boolValue: Bool { return self != 0 } init?(jsonObject: Any?) { if let number = jsonObject as? NSNumber { self = number.intValue } else if let string = jsonObject as? NSString { self = string.integerValue } else { return nil } } } extension Bool { init?(jsonObject: Any?) { if let integer = Int(jsonObject: jsonObject) { self = integer.boolValue } else { return nil } } } extension Double { init?(jsonObject: Any?) { if let number = jsonObject as? NSNumber { self = number.doubleValue } else if let string = jsonObject as? NSString { self = string.doubleValue } else { return nil } } }
All objects produced by JSONSerialization are instances of NSString, NSNumber, NSArray, NSDictionary, or NSNull.