Ravi Shankar

Tweaking Apps

NSUnknownKeyException – this class is not key value coding-compliant for the key

By Leave a Comment

NSUnknownKeyException – this class is not key value coding-compliant for the key common error that most of the Swift beginners would face during the learning period.

Terminating app due to uncaught exception ‘NSUnknownKeyException’, reason: ‘[<Handbook.StudentEntryController 0x78f948a0> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key nametxt.’
*** First throw call stack:
(
0 CoreFoundation 0x02316a14 __exceptionPreprocess + 180
1 libobjc.A.dylib 0x01751e02 objc_exception_throw + 50
2 CoreFoundation 0x02316631 -[NSException raise] + 17
3 Foundation 0x013e71bc -[NSObject(NSKeyValueCoding) setValue:forUndefinedKey:] + 282
4 Foundation 0x0134183a _NSSetUsingKeyValueSetter + 115
5 Foundation 0x013417bf -[NSObject(NSKeyValueCoding) setValue:forKey:] + 295
6 UIKit 0x02cac06d -[UIViewController setValue:forKey:] + 85
7 Foundation 0x0137601d -[NSObject(NSKeyValueCoding) setValue:forKeyPath:] + 384
8 UIKit 0x02f1fcb4 -[UIRuntimeOutletConnection connect] + 132
9 libobjc.A.dylib 0x0176600c -[NSObject performSelector:] + 62
10 CoreFoundation 0x02246f51 -[NSArray makeObjectsPerformSelector:] + 273
11 UIKit 0x02f1e34e -[UINib instantiateWithOwner:options:] + 2102
12 UIKit 0x02cb3abc -[UIViewController _loadViewFromNibNamed:bundle:] + 429
13 UIKit 0x02cb44f4 -[UIViewController loadView] + 189
14 UIKit 0x02f47b66 -[UITableViewController loadView] + 88
15 UIKit 0x02cb4900 -[UIViewController loadViewIfRequired] + 154
16 UIKit 0x02cbb406 -[UIViewController __viewWillAppear:] + 114
17 UIKit 0x02cde5b9 -[UIViewController(UIContainerViewControllerProtectedMethods) beginAppearanceTransition:animated:] + 202
18 UIKit 0x02cf09cc -[UINavigationController _startCustomTransition:] + 1389
19 UIKit 0x02d02769 -[UINavigationController _startDeferredTransitionIfNeeded:] + 803
20 UIKit 0x02d03ada -[UINavigationController __viewWillLayoutSubviews] + 68
21 UIKit 0x02edfc4a -[UILayoutContainerView layoutSubviews] + 252
22 UIKit 0x02bb5008 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 810
23 libobjc.A.dylib 0x01766059 -[NSObject performSelector:withObject:] + 70
24 QuartzCore 0x029b480a -[CALayer layoutSublayers] + 144
25 QuartzCore 0x029a84ee _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 388
26 QuartzCore 0x029a8352 _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 26
27 QuartzCore 0x0299ae8b _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 317
28 QuartzCore 0x029cee03 _ZN2CA11Transaction6commitEv + 561
29 QuartzCore 0x029d0674 _ZN2CA11Transaction17flush_transactionEv + 50
30 UIKit 0x02ae28bc _UIApplicationHandleEventQueue + 8398
31 CoreFoundation 0x022306ff __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 15
32 CoreFoundation 0x0222638b __CFRunLoopDoSources0 + 523
33 CoreFoundation 0x022257a8 __CFRunLoopRun + 1032
34 CoreFoundation 0x022250e6 CFRunLoopRunSpecific + 470
35 CoreFoundation 0x02224efb CFRunLoopRunInMode + 123
36 GraphicsServices 0x05cf5664 GSEventRunModal + 192
37 GraphicsServices 0x05cf54a1 GSEventRun + 104
38 UIKit 0x02ae8bfa UIApplicationMain + 160
39 Handbook 0x0007513d main + 93
40 libdyld.dylib 0x04b11a21 start + 1
41 ??? 0x00000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

This issue occurs when a storyboard refers to a deleted or renamed IBOutlet. If you navigate to the connection instepctor of the ViewController, you shoud notice an exclaimation mark as shown below.

Remove the IBOutlet mapping by clicking on X mark and remove the orphaned IBOutlet.

Swift – WebView demo

By 24 Comments

Updated for Swift 5

In this short tutorial, we will see an example in Swift programming language using UIWebView. The WebView will load a webpage and provide option to refresh, stop, go back and go forward. This tutorial should give a brief overview on how to declare IBAction, IBOutlets and use Objective-C classes (NSURL and NSURLRequest) in Swift


Interface Design

Step 1: Create a Single View Application Project and make sure to select the programming language as Swift

Choose Swift Language in Xcode

Step 2: Select Main.Storyboard under Project navigator. then drag and drop WebView and Toolbar from Object Library to the View Controller.

Step 3: Now place four bar button items on Toolbar to provide stop, refresh, go back and go forward functionality. You can also use flexible and fixed separators for aligning the bar button items.

Use Suggested Constraints in Xcode 6

Step 4: Make sure to use the SuggestedConstraints for WebView and Toolbar. You can do this by selecting the controls and using the Reset to Suggested Constraints available as part of Resolve Auto Layout option. This would ensure that the controls gets adjusted automatically depending upon the device’s screen width and height.

Reset to Suggested Constraints

Updated – 28/08/2014

Since some users are facing problems with Reset to Suggested Constraints in Xcode 6 Beta 6, you can use Pin option to define the four constraints using the default values. Then click Add 4 Constraints available at the bottom of the screen.

201408281213.jpg

Write Code

Step 5: Navigate to ViewController.swift file on the Project Navigator. Add the following line after class ViewController: UIViewController which defines the IBOutlet element for WebView.

@IBOutlet var webView: UIWebView!

Then connect this IBOutlet element to the WebView on InterfaceBuilder.

Step 6: In the viewDidLoad function, create URL and NSURLRequest for the webpage and associate this with the WebView by calling loadRequest method.

override func viewDidLoad() 
{   
  super.viewDidLoad() 
  let url = NSURL(string: "https://rshankar.com")
  let request = NSURLRequest(url: url! as URL)       
  webView.delegate = self
  activityIndicator.hidesWhenStopped = true
  activityIndicator.startAnimating()
  webView.loadRequest(request as URLRequest) 
}

Step 7: Now add the corresponding IBAction methods for the four buttons stop, refresh, go back and go forward. And connect these IBActions to the buttons on Interface builder.

func webViewDidFinishLoad(_ webView: UIWebView) 
{ 
      activityIndicator.stopAnimating()   
}                                                                                           

@IBAction func doRefresh(_: AnyObject) {                                                              
  webView.reload()
}

@IBAction func goBack(_: AnyObject) 
{   
   webView.goBack()    
}

@IBAction func goForward(_: AnyObject) {
  webView.goForward()
}

@IBAction func stop(_: AnyObject) 
{
   webView.stopLoading()
}

Step 8: Compile and run the project by selecting a suitable simulator.

Download the souce code from GitHub.

Unable to simultaneously satisfy constraints.

By

A common error that we would see when using Auto Layout is

Unable to simultaneously satisfy constraints. Probably at least one of the constraints in the following list is one you don’t want.

Debugging the verbose shown in the console might look difficult but if you closely go through the messages you should be able to identify the issue.

Let us take the following Auto Layout Constraint error messages.

Try this:
(1) look at each constraint and try to figure out which you don’t expect;
(2) find the code that added the unwanted constraint or constraints and fix it.
(
“<NSLayoutConstraint:0x281862940 UIImageView:0x14ddb28e0.width == UIImageView:0x14ddb28e0.height (active)>”,
“<NSLayoutConstraint:0x28181c190 V:|-(5)-[UIImageView:0x14ddb28e0] (active, names: ‘|’:UITableViewCellContentView:0x14ddb2750 )>”,
“<NSLayoutConstraint:0x28181cc30 UIImageView:0x14ddb28e0.width == 0.22*UITableViewCellContentView:0x14ddb2750.width (active)>”,
“<NSLayoutConstraint:0x28181eb20 V:[UIImageView:0x14ddb28e0]-(5)-| (active, names: ‘|’:UITableViewCellContentView:0x14ddb2750 )>”,
“<NSLayoutConstraint:0x28186e080 ‘UIView-Encapsulated-Layout-Height’ UITableViewCellContentView:0x14ddb2750.height == 93 (active)>”,
“<NSLayoutConstraint:0x28186e030 ‘UIView-Encapsulated-Layout-Width’ UITableViewCellContentView:0x14ddb2750.width == 375 (active)>”
)

Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x281862940 UIImageView:0x14ddb28e0.width == UIImageView:0x14ddb28e0.height (active)>

The constraints associated with this UIImageView are

This error is result of more than one constraints staistying the same condition. The last line in the log message tells one of the constraint causes this issues. “width == height”. Now identify the second constraint which tries to set the width of this imageview.

There are two constraints trying to set the width for the image view, 1. Propotional Width to and 2. Aspect Ratio. After removing the unwanted constraint and you are good to go.

Let us see one more example for the Constraint errors.

(
“<NSLayoutConstraint:0x281818f00 UIButton:0x14ddb7fe0’BOOK’.height == 50 (active)>”,
“<NSLayoutConstraint:0x28186c050 V:|-(20)-[UIButton:0x14ddb7fe0’BOOK’] (active, names: ‘|’:UITableViewCellContentView:0x14ddb7e50 )>”,
“<NSLayoutConstraint:0x28186c0a0 V:[UIButton:0x14ddb7fe0’BOOK’]-(20)-| (active, names: ‘|’:UITableViewCellContentView:0x14ddb7e50 )>”,
“<NSLayoutConstraint:0x28181aad0 ‘UIView-Encapsulated-Layout-Height’ UITableViewCellContentView:0x14ddb7e50.height == 90.5 (active)>”
)

Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x281818f00 UIButton:0x14ddb7fe0’BOOK’.height == 50 (active)>

 

The last line gives a clue, there are two constraints trying to set the height of the BOOK button. And if you look at the constraints for the BOOK button, you can find 1. Top and Bottom constraints are set for button and 2. Height constraint is also set for Button. Removing any one of the constraint would fix the problem.

Upload missing dSYMs to see crashes

By

If you are using Firebase Crasyltics in your app and if bitcode is enabled then you might see this message

“Upload missing dSYMs to see crashes” when trying to view reported crash in Firebase Crashlytics. In order the see the stack trace, you can try uploading the dSYMs files.

Compress .dSYMs files.

  • Launch Xcode Organizer.
  • Select the App on the Right hand side and navigate to the version which caused the crash.
  • Right click on the version and select Show in Finder.

  • Right click the archive file and select “Show Package Contents”.
  • Copy all the dSYMs files to another location.
  • Compress the file and upload the compress file to Firebase to see see the stack trace.

iTunesConnect

Another option is to download dSYMs files from iTunes Connect.

Select your App -> Activity section -> Select the Version -> Download dSYSM

Protect WhatsApp with Touch ID in iPhone

By Leave a Comment

Now you can lock WhatsApp on your iPhone with Touch ID. If your phone is being accessed by family memebers then this would be quite helpful to prevent other users from accessing your WhatsApp message.

Steps to enable Touch ID for WhatsApp

  1. Tap Settings on your WhatsApp app.

  2. In the Setting screen, navigate to Privacy option.

  3. Scrolled down the Privacy screen and select Screen Lock from the list.

  4. Now this will have the option to enable or disable Touch ID for WhatsApp. This also provides option to set the time of lock to appear whether immediately or after certain time.

How to rename multiple files on a Mac

By Leave a Comment

Let us say you are scanning documents using a printer connected to a Mac. And when scanning multiple pages of the same document, the pages gets scanned with the default name followed by a ordered number.

As shown in the above screenshot, the filename starts with Screenshot and prefixed with some numbers.

Rename all files at once

All these files can be renamed all at once using below mentioned steps.

  1. Select all files and right click the selected items.

  2. Select Rename n items options from the listed menus.
  3. Provide a name in the Custom Format field. Let us name this as PropertyDocument.

  4. Enter the start number for the pages then click Rename button.

Now all the files will appear with name as PropertyDocument followed by a number.

Journey with Swift

By

This is about my journey as a Swift developer and some of the points discussed here could be useful to anyone who want to re-invent themselves as a software developer or if they want start a career as a Software developer.

Past experience

I have been working in Software industry for years in wide range of technologies. Like many I felt the need for a change and wanted to switch over to the latest technologies. I was interested in iOS app development though I started with Objective-C within a year switched to Swift.

Be an early adopter

Choosing the technology matters and if you are one of the early adopter then you get new opportunities quickly. Being one of the early adapter of Swift helped me a lot to get noticed quickly. Also if the technology has the backing of some big corporates then you will grow with the technology.

Blog a learning tool

I started writing simple tutorials in Swift and shared this with the wider audience through my blog. This helped me to articulate the concepts well and also get valuable feedback from readers. In the later stage I got many opportunities/leads through my blog. Check out Ash Furrow and Kristina Thai talks on the benefiting of writing a blog.

Stay focussed

After picking up iOS/Swift, I got distracted time and again with Android and other hybrid platforms. But remember the process of learning any technology is the same and you are not going to achieve your goal by focussing on different platforms at the same time. Stay focussed to reach your goal quickly.

Build a portfolio

Another way of building confidence is to publish apps under your name. You can start with simple apps and increase the features as you gain more and more experience. I sometimes felt embarrased with the choice of initial apps that I made and the code that I wrote. It is quite natural to feel that way as long you keep learning continuously

Eat Swift, Sleep Swift, Breathe Swift

Don’t put all your eggs in one basket. I was working as a Objective-C developer but quit the job to focus only on Swift. There were not many gigs available during the first year hence become an iOS mentor. The best way to keep learning is by teaching others. This allowed me to spend all my time in learning and practising Swift.

Networking and team events

Join local meet-ups learn from other like minded people. If possible attend conferences where you get a chance to meet some international speakers as well. Participate in Hackathons and test your ability in new technologies by conceptualising the app idea in to MVP in the short period of time.

Take up new opportunities

I got a lead through my blog for reviewing a Swift book and also to co-author a Udemy course. Don’t hesitate to take up new opportunities as long as it aligns with your technology. This can alway add up to your portfolio and online presence.

Hard work, dedication!

After many unsuccessful bidding finally I got a small prototype work in Swift. The client again awarded me a full fledged project which later become a full-time work. Even if it is a small gig, hard work and dedication definitely pays off.

 

I want to end with one quote this is especially for the people in their 30s & 40s. You can become or re-invent yourself as software developer at any age. “Age is no barrier. It’s a limitation you put on your mind”. Don’t compare yourself with other developers know your strength and work around your limitations. Happy Coding!!