I have two ViewControllers, which I am trying to pass a NSURLRequest through a delegate.
Here is the delegate:
protocol URLRequestDelegate{
func urlRequest(url: NSURLRequest)
}
The delegate is successfully passing the NSURLRequest, because I have error checked it.
However in the ViewController the delegate is passing the NSURLRequest to, I have implemented the required function to conform to the protocol which is where I use the function webView.loadRequest() to load the webView with the desired webpage.
The webView is done through code and not storyboard:
var webView: UIWebView = UIWebView(frame: CGRect(x: 0, y: 0, width: UIScreen.mainScreen().bounds.width, height: UIScreen.mainScreen().bounds.height))
Here is that function:
func urlRequest(url: NSURLRequest) {
//Load URL from the delegate.
webView.loadRequest(url)
}
But this does't load the UIWebView with the NSURLRequest passed in the delegate, I am thinking that the delegate method func urlRequest() isn't calling correctly or maybe before viewDidLoad() method.
I have even set the self.view.webView.delegate = selfand implemented the UIWebViewDelegate on this class and implemented the func viewDidStartLoad() & fun viewDidFinishLoad with println() inside them to check to see if the codes being run when I call webView.loadRequest(url) however they never seem to be printed of.
So this leaves me puzzled, because I'm not quite sure what is causing the .loadRequest() not to function correctly within the delegate method func urlRequest().
I do know that if I put .loadRequest() within viewDidLoad() with lets say a hardcoded url of http://www.google.com it does work. However I can't pass the delegates NSURLRequest within viewDidLoad() as it has to be implemented inside func urlRequest() to conform correctly to the protocol.
Did you make sure to set the delegate for your first ViewController? You first ViewController needs to have a property of type URLRequestDelegate and you need to set that property equal to your second ViewController at some point.
Related
Using swift3 with xcode8
Below is my viewconroller.swift
class ViewController: UIViewController {
#IBOutlet weak var YahooWebview: UIWebView!
#IBOutlet weak var activity: UIActivityIndicatorView!
override func viewDidLoad() {
super.viewDidLoad()
let YURL = URL(string: "http://www.yahoo.com")
let YURLRequest = URLRequest(url: YURL!)
YahooWebview.loadRequest(YURLRequest)
}
}
func webViewDidStartLoad(YahooWebview: UIWebView) {
activity.startAnimating()
}
func webViewDidFinishLoad(YahooWebview: UIWebView) {
print("show indicator")
activity.stopAnimating()
}
Why my indicator is not showing when webview is loading?
I can not even see string "show indicator" from my log in Xcode.
You need to set your class as the delegate of UIWebView as
YahooWebview.delegate = self
Check my answer to get details regarding delegates and delegation pattern.
Note from apple developer: In apps that run in iOS 8 and later, use the
WKWebView class instead of using UIWebView. Additionally, consider setting the WKPreferences property javaScriptEnabled to false if you render files that are not supposed to run JavaScript.
There can be two problems as mentioned in comments.
Both can be solved in your Stroyboard/xib file.
Your UIActivityIndicatorView is may be hidden behind UIWebView. Just change the position of the view so that it comes above in the view heirarchy.
You may not have set delegate property of UIWebview class as your ViewController. Right click on webview and check. This needs to be set as you are animating the activity indicator view inside delegate methods.
i want to ask that how the protocols and delegation patterns functions in Swift.
I have an application that let me try the google ad sdk on iOS platform. But i'm missing something and confused about how the methods works.
I have some codes like these;
import UIKit
import GoogleMobileAds
class ViewController: UIViewController, GADInterstitialDelegate {
#IBOutlet weak var bannerView: GADBannerView!
let request = GADRequest()
var interstitial: GADInterstitial!
#IBOutlet weak var mylbl: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
bannerView.adUnitID = "xxx"
bannerView.rootViewController = self
bannerView.loadRequest(self.request)
interstitial = createAndLoadInterstitial()
}
func createAndLoadInterstitial() -> GADInterstitial {
let interstitial = GADInterstitial(adUnitID: "xxx")
interstitial.delegate = self
interstitial.loadRequest(self.request)
return interstitial
}
func interstitialDidDismissScreen(ad: GADInterstitial!) {
interstitial = createAndLoadInterstitial()
mylbl.text = "No ad"
}
func interstitialDidReceiveAd(ad: GADInterstitial!) {
mylbl.text = "received ad"
}
#IBAction func touched(sender: AnyObject) {
if interstitial.isReady
{
interstitial.presentFromRootViewController(self)
}
else
{
mylbl.text = "Not Ready!"
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
For the code above, i'm aware of that the protocols blueprints of methods and properties to adopt a class or struct or enum. The methods or properties defined in the protocol should be implemented on the class that adopted by the related delegate.
I want to ask that and cofused point: OK the method which is named "interstitialDidDismissScreen" inherited from the delegate "GADInsterstitialDelegate" but how the method handled by pressing the close button of the interstitial ad. Where the engineers of Google implemented and how they succeed this behavior. Thanks for your help.
Good hacks,
The button handling is taking place inside the GADInterstitial class. When they setup the class they probably have some internal methods that handle all the ad interaction, and then using the delegate methods they send back to your class the info you need to know to keep your UI managed. By implementing the delegate and its methods you've said I want to use something that your class does, and then I want to also handle all the feedback from that class. If you were to make your own class and implement a protocol and delegate you could do whatever you want inside your class and then pass back just a sliver of info to the class' delegate. An example would be a barcode reading class. I don't care how the barcode gets read, I just want to know the code, so I could set my calling class to be the delegate of the barcode reading class, and when the barcode is read I would receive the barcode back inside of a barcode delegate method.
The wording of your question is garbled and hard to figure out.
A protocol is basically a contract. It says that objets that conform to the protocol promise to provide the properties, and respond to the methods that the protocol defines.
When you say
someObject.delegate = self
You are passing a pointer to yourself to the other object. This is like giving somebody your phone number and saying "Please run these errands for me. If you have any questions, call me at this number. Also please call me when the errands are done."
Since the other object knows that it's delegate conforms to a specific protocol, it knows what messages it can send over the phone (what messages it can send to the delegate)
I suspect the methods interstitialDidReceiveAd(ad: GADInterstitial!) and interstitialDidDismissScreen(ad: GADInterstitial!) are delegate methods.
When the interstitial object needs to send messages to it's delegate, it calls these methods.
I read a lot about the delegates but in practice I cannot use it properly.
Description: I have A: UIViewController, B: UIView, C: UIViewController. I want to run segue from A: UIViewController to the C: UIViewController from the inside of B: UIView.
I've tried:
protocol SegueDelegate {
func runSegue(identifier: String)
}
class B: UIView { ... }
where in my A: UIViewController:
override func viewDidLoad() {
B().delegate = self
}
func runSegue(identifier: String) {
self.performSegueWithIdentifier(identifier, sender: self)
}
and trying to call it via:
#IBAction func send(sender: AnyObject) {
let a: SegueDelegate? = nil
a!.runSegue("goToMainPage")
}
but I'm sure that I do not use it properly. Can anyone help me with it? I do not want just an answer. Please describe me it concept shortly
Delegates are just a Design Pattern that you can use in a number of ways. You can look at the Apple Frameworks to see how and where to use delegates as examples. A table view delegate is probably the best known delegate in UIKit.
Delegates serve as a callback mechanism for code to communicate with an instance of an unknown class without knowing more than that that instance will respond to the methods of the delegate protocol.
An alternative to a delegate is to use a closure (what we used to call a block in Objective-C). When to use one vs. the other is a matter of taste. There are a couple of rules of thumb, like for instance outlined here.
What you are doing is, IMO, the proper way to use delegates. You separate the view functionality from the View Controller's functionalities via a delegate, and so the contract for your view is clear: the user needs to respond to the delegate method.
Your code works and is correct. I made a quick implementation here: https://github.com/kristofvanlandschoot/DelegateUsage/tree/master
The main difference from your example, and maybe that's the place where you made a mistake is the third part of your code where you should write something like:
#IBAction func send(sender: AnyObject) {
delegate?.runSegue("segueAB")
}
There are multiple errors in your code, for example:
Here you are creating a new B, and setting A as a delegate of that new instance, no the one you actually want
override func viewDidLoad() {
«B()».delegate = self
}
And here you are creating force unwrapping a nil value
#IBAction func send(sender: AnyObject) {
let a: SegueDelegate? = «nil»
«a!».runSegue("goToMainPage")
}
If what you want to do is tell A to perform a segue to C, from inside B, all you need to do is to call performSegueWithIdentifier on A
For example:
class B: UIView {
weak var referenceToA: UIViewController? = nil // set this somewhere
#IBAction func send(sender: AnyObject) {
guard let a = referenceToA else {
fatalError("you didn't set the reference to a view controller of class A")
}
a.performSegueWithIdentifier("goToMainPage", sender: self)
}
}
I have been pulling my hair out trying to get this 'Delegate' thing to work in Swift for an App I am working on.
I have two files: CreateEvent.swift and ContactSelection.swift, where the former calls the latter.
CreateEvent's contents are:
class CreateEventViewController: UIViewController, ContactSelectionDelegate {
/...
var contactSelection: ContactSelectionViewController = ContactSelectionViewController()
override func viewDidLoad() {
super.viewDidLoad()
/...
contactSelection.delegate = self
}
func updateInvitedUsers() {
println("this finally worked")
}
func inviteButton(sender: AnyObject){
invitedLabel.text = "Invite"
invitedLabel.hidden = false
toContactSelection()
}
/...
func toContactSelection() {
let contactSelection = self.storyboard?.instantiateViewControllerWithIdentifier("ContactSelectionViewController") as ContactSelectionViewController
contactSelection.delegate = self
self.navigationController?.pushViewController(contactSelection, animated: true)
}
ContactSelection's contents are:
protocol ContactSelectionDelegate {
func updateInvitedUsers()
}
class ContactSelectionViewController: UITableViewController {
var delegate: ContactSelectionDelegate?
override func viewDidLoad() {
super.viewDidLoad()
self.delegate?.updateInvitedUsers()
}
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
// Stuff
self.delegate?.updateInvitedUsers()
}
}
What am I doing wrong? I am still new and don't fully understand this subject but after scouring the Internet I can't seem to find an answer. I use the Back button available in the Navigation Bar to return to my CreateEvent view.
var contactSelection: ContactSelectionViewController = ContactSelectionViewController()
This is instantiating a view controller directly, and the value never gets used. Since it looks like you're using storyboards, this isn't a good idea since none of the outlets will be connected and you'll get optional unwrapping crashes. You set the delegate of this view controller but that's irrelevant as it doesn't get used.
It also isn't a good idea because if you do multiple pushes you'll be reusing the same view controller and this will eventually lead to bugs as you'll have leftover state from previous uses which might give you unexpected outcomes. It's better to create a new view controller to push each time.
In your code you're making a brand new contactSelection from the storyboard and pushing it without setting the delegate.
You need to set the delegate on the instance that you're pushing onto the navigation stack.
It's also helpful to pass back a reference in the delegate method which can be used to extract values, rather than relying on a separate reference in the var like you're doing.
So, I'd do the following:
Remove the var contactSelection
Add the delegate before pushing the new contactSelection object
Change the delegate method signature to this:
protocol ContactSelectionDelegate {
func updateInvitedUsers(contactSelection:ContactSelectionViewController)
}
Change your delegate calls to this:
self.delegate?.updateInvitedUsers(self)
I've been playing around with web views in swift this evening, but have run into a bit of an issue.
For some reason I'm not able to get the webViewDidStartLoad or webViewDidFinishLoad methods to fire.
In my storyboard, I have an outlet called webView linked to my UIWebView element.
Is anyone able to help me with what I am doing wrong?
This is my viewController.swift file:
import UIKit
class ViewController: UIViewController, UIWebViewDelegate {
#IBOutlet var webView : UIWebView
var url = NSURL(string: "http://google.com")
override func viewDidLoad() {
super.viewDidLoad()
//load initial URL
var req = NSURLRequest(URL : url)
webView.loadRequest(req)
}
func webViewDidStartLoad(webView : UIWebView) {
//UIApplication.sharedApplication().networkActivityIndicatorVisible = true
println("AA")
}
func webViewDidFinishLoad(webView : UIWebView) {
//UIApplication.sharedApplication().networkActivityIndicatorVisible = false
println("BB")
}
}
Try this!
var req = NSURLRequest(URL: url)
webView.delegate = self
webView.loadRequest(req)
I experienced the same issue, even I did confirmed the UIWebViewDelete to self and implemented its methods.
//Document file url
var docUrl = NSURL(string: "https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwjjwPSnoKfNAhXFRo8KHf6ACGYQFggbMAA&url=http%3A%2F%2Fwww.snee.com%2Fxml%2Fxslt%2Fsample.doc&usg=AFQjCNGG4FxPqcT8RXiIRHcLTu0yYDErdQ&sig2=ejeAlBgIZG5B6W-tS1VrQA&bvm=bv.124272578,d.c2I&cad=rja")
let req = NSURLRequest(URL: docUrl!)
webView.delegate = self
//here is the sole part
webView.scalesPageToFit = true
webView.contentMode = .ScaleAspectFit
webView.loadRequest(req)
above logic worked perfectly with test URl I got from quick google search.
But I when I replaced with mine. webViewDidFinishLoad never get called.
then How we solved?
On backed side we had to define content-type as document in headers. and it works like charm.
So please make sure on your server back-end side as well.
Here's my 2 cents battling with the same problem in SWIFT 3:
class HintViewController: UIViewController, UIWebViewDelegate
Declare the delegate methods this way (note the declaration of the arguments):
func webViewDidStartLoad(_ webView: UIWebView)
func webViewDidFinishLoad(_ webView: UIWebView)
Remember to set self to the webview's delegate property either in Interface Builder (Select the webview, drag from the delegate outlet to the webview from the Connections Inspector OR programmatically: self.webview.delegate = self)
As others noted, setting the delegate of UIWebView and conforming to the UIWebViewDelegate protocol is the best possible solution out there.
For other's who might make it here. I had put my delegate methods in a private extension which couldn't be accessed by the delegate caller. Once I changed the extension to internal the delegates started to get called properly.
There is my detailed solution for Swift 3:
1) in class declaration write the UIWebViewDelegate. For example:
class MyViewController: UIViewController, UIWebViewDelegate {
2) of course in storyboard make link to your UIViewController like this:
#IBOutlet weak var webView: UIWebView!
3) in the func viewDidLoad add one line:
self.webView.delegate = self
Nothing more. Special thinks to LinusGeffarth and LLIAJLbHOu for idea.