How to construct a ScrollView using Swift? - ios

Question

I'm constructing my first App for IOS and I'm struggling to find a way to do a simple ScrollView using the Swift code on the XCode6, please can someone help me to find the solution?
My problem is that I don't know how to make the scrollview work in my code. I already putted the code as you can see below in the ViewController.swift and I was expecting to be able to select the Outlet "scroller" in the Main.storyboard for a ViewController, instead of this I'm receiving the error *"fatal error: Can't unwrap Optional.None (lldb)"* EXC_BAD_INSTRUCTION (code=EXC_1386_INVOP, subcode=0x0)
I have some ViewController screens and in one of that I putted one ScrollView and I want to make it works using the Swift.
I'm stuck on this:
import UIKit
class ViewController: UIViewController {
#IBOutlet var scroller:UIScrollView
override func viewDidLoad() {
super.viewDidLoad()
scroller.scrollEnabled = true;
scroller.contentSize = CGSizeMake(320, 624);
// Do any additional setup after loading the view, typically from a nib.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
I think if someone can provide a simple example how to do a scrollview using swift it will solve my problem. Any help is appreciate.
Trying to do it in a old style I tried to do it using a .m and .h file:
ViewController.m
#import "Amigo-Bridging-Header.h"
#interface ViewController ()
#end
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
[scroller setScrollEnabled:YES];
[scroller setContentSize:CGSizeMake(320, 624)];
// Do any additional setup after loading the view, typically from a nib.
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#end
Amigo-Bridging-Header.h
#import <UIKit/UIKit.h>
#interface ViewController : UIViewController {
IBOutlet UIScrollView *scroller;
}
#end
Cheers

Answer 1

Let's give this a shot. The one thing to note is I have yet to find a way to downcast self.view as a UIScrollView, so you can't make calls like self.view.contentOffset.
import UIKit
class ScrollingViewController : UIViewController {
// Create a scrollView property that we'll set as our view in -loadView
let scrollView = UIScrollView(frame: UIScreen.mainScreen().bounds)
override func loadView() {
// calling self.view later on will return a UIView!, but we can simply call
// self.scrollView to adjust properties of the scroll view:
self.view = self.scrollView
// setup the scroll view
self.scrollView.contentSize = CGSize(width:1234, height: 5678)
// etc...
}
func example() {
let sampleSubView = UIView()
self.view.addSubview(sampleSubView) // adds to the scroll view
// cannot do this:
// self.view.contentOffset = CGPoint(x: 10, y: 20)
// so instead we do this:
self.scrollView.contentOffset = CGPoint(x: 10, y: 20)
}
}

Answer 2

Your outlet is not connected. From the Swift with objective-C book:
When you declare an outlet in Swift, the compiler automatically converts the type to a weak implicitly unwrapped optional and assigns it an initial value of nil. In effect, the compiler replaces #IBOutlet var name: Type with #IBOutlet weak var name: Type! = nil
If this value was not connected, it would remain as nil and you'd get a runtime error when accessing the value.

Answer 3

#IBOutlet weak var scrollView: UIScrollView!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
// setup the scroll view
self.scrollView.contentInset = UIEdgeInsetsMake(0, 0, 200, 0);
}