&gt;[You cannot subclass a Swift class in Objective-C.](https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/CollectionTypes.html#//apple_ref/doc/uid/TP40014097-CH8-XID_133)

Excerpt from [Using Swift with Cocoa and Objective-C](https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/BuildingCocoaApps/MixandMatch.html#//apple_ref/doc/uid/TP40014216-CH10-NoLink_26)

You cannot subclass a Swift class in Objective-C. cf. towards the end of [this section of the docs](https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/BuildingCocoaApps/MixandMatch.html#//apple_ref/doc/uid/TP40014216-CH10-XID_84):
&gt; However, note that you cannot subclass a Swift class in Objective-C.

It&#39;s an compiling error, so U can not subclass a swift class in objc.  
    

    SWIFT_CLASS(&quot;_TtC6Swifty14ViewController&quot;)
    @interface ViewController : UIViewController
    @end


    # if defined(__has_attribute) &amp;&amp; __has_attribute(objc_subclassing_restricted)
    #  define SWIFT_CLASS(SWIFT_NAME) SWIFT_RUNTIME_NAME(SWIFT_NAME) __attribute__((objc_subclassing_restricted)) SWIFT_CLASS_EXTRA
    #  define SWIFT_CLASS_NAMED(SWIFT_NAME) __attribute__((objc_subclassing_restricted)) SWIFT_COMPILE_NAME(SWIFT_NAME) SWIFT_CLASS_EXTRA
    # else
    #  define SWIFT_CLASS(SWIFT_NAME) SWIFT_RUNTIME_NAME(SWIFT_NAME) SWIFT_CLASS_EXTRA
    #  define SWIFT_CLASS_NAMED(SWIFT_NAME) SWIFT_COMPILE_NAME(SWIFT_NAME) SWIFT_CLASS_EXTRA
    # endif
    #endif

How do I create a noop block for a switch case in Swift? Swift forces you to have at least one executable statement under your case, including default.  I tried putting an empty { } but Swift won&#39;t take that.  Which means that Swift&#39;s switch case is not totally translatable between if-else and vice versa because in if-else you are allowed to have empty code inside the condition.

e.g.

    switch meat {
    
       case &quot;pork&quot;:
         print(&quot;pork is good&quot;)
    
       case &quot;poulet&quot;:
         print(&quot;poulet is not bad&quot;)
    
       default:
         // I want to do nothing here
    }



How do I create a noop block for a switch case in Swift?

I have the following code:

    # returns string w/o leading or trailing whitespace
    trim &lt;- function (x) gsub(&quot;^\\s+|\\s+$&quot;, &quot;&quot;, x)

    news_corpus &lt;- Corpus(VectorSource(news_raw$text)) # a column of strings.

    corpus_clean &lt;- tm_map(news_corpus, tolower)
    corpus_clean &lt;- tm_map(corpus_clean, removeNumbers)
    corpus_clean &lt;- tm_map(corpus_clean, removeWords, stopwords(&#39;english&#39;))
    corpus_clean &lt;- tm_map(corpus_clean, removePunctuation)
    corpus_clean &lt;- tm_map(corpus_clean, stripWhitespace)
    corpus_clean &lt;- tm_map(corpus_clean, trim)
    
    news_dtm &lt;- DocumentTermMatrix(corpus_clean) # errors here

When I run the `DocumentTermMatrix()` method, it gives me this error:

&gt; Error: inherits(doc, &quot;TextDocument&quot;) is not TRUE

Why do I get this error?  Are my rows not text documents?

Here is the output upon inspecting `corpus_clean`:

    [[153]]
    [1] obama holds technical school model us
    
    [[154]]
    [1] oil boom produces jobs bonanza archaeologists
    
    [[155]]
    [1] islamic terrorist group expands territory captures tikrit
    
    [[156]]
    [1] republicans democrats feel eric cantors loss
    
    [[157]]
    [1] tea party candidates try build cantor loss
    
    [[158]]
    [1] vehicles materials stored delaware bridges
    
    [[159]]
    [1] hill testimony hagel defends bergdahl trade
    
    [[160]]
    [1] tweet selfpropagates tweetdeck
    
    [[161]]
    [1] blackwater guards face trial iraq shootings
    
    [[162]]
    [1] calif man among soldiers killed afghanistan
    
    [[163]]
    [1] stocks fall back world bank cuts growth outlook
    
    [[164]]
    [1] jabhat alnusra longer useful turkey
    
    [[165]]
    [1] catholic bishops keep focus abortion marriage
    
    [[166]]
    [1] barbra streisand visits hill heart disease
    
    [[167]]
    [1] rand paul cantors loss reason stop talking immigration
    
    [[168]]
    [1] israeli airstrike kills northern gaza

**Edit:** Here is my data:

    type,text
    neutral,The week in 32 photos
    neutral,Look at me! 22 selfies of the week
    neutral,Inside rebel tunnels in Homs
    neutral,Voices from Ukraine
    neutral,Water dries up ahead of World Cup
    positive,Who&#39;s your hero? Nominate them
    neutral,Anderson Cooper: Here&#39;s how
    positive,&quot;At fire scene, she rescues the pet&quot;
    neutral,Hunger in the land of plenty
    positive,Helping women escape &#39;the life&#39;
    neutral,A tour of the sex underworld
    neutral,Miss Universe Thailand steps down
    neutral,China&#39;s &#39;naked officials&#39; crackdown
    negative,More held over Pakistan stoning
    neutral,Watch landmark Cold War series
    neutral,In photos: History of the Cold War
    neutral,Turtle predicts World Cup winner
    neutral,What devoured great white?
    positive,Nun wins Italy&#39;s &#39;The Voice&#39;
    neutral,Bride Price app sparks debate
    neutral,China to deport &#39;pork&#39; artist
    negative,Lightning hits moving car
    neutral,Singer won&#39;t be silenced
    neutral,Poland&#39;s mini desert
    neutral,When monarchs retire
    negative,Murder on Street View?
    positive,Meet armless table tennis champ
    neutral,Incredible 400 year-old globes
    positive,Man saves falling baby
    neutral,World&#39;s most controversial foods

Which I retrieve like:

    news_raw &lt;- read.csv(&#39;news_csv.csv&#39;, stringsAsFactors = F)

**Edit:** Here is the traceback():

    &gt; news_dtm &lt;- DocumentTermMatrix(corpus_clean)
    Error: inherits(doc, &quot;TextDocument&quot;) is not TRUE
    &gt; traceback()
    9: stop(sprintf(ngettext(length(r), &quot;%s is not TRUE&quot;, &quot;%s are not all TRUE&quot;), 
           ch), call. = FALSE, domain = NA)
    8: stopifnot(inherits(doc, &quot;TextDocument&quot;), is.list(control))
    7: FUN(X[[1L]], ...)
    6: lapply(X, FUN, ...)
    5: mclapply(unname(content(x)), termFreq, control)
    4: TermDocumentMatrix.VCorpus(x, control)
    3: TermDocumentMatrix(x, control)
    2: t(TermDocumentMatrix(x, control))
    1: DocumentTermMatrix(corpus_clean)

When I evaluate `inherits(corpus_clean, &quot;TextDocument&quot;)` it is FALSE.

DocumentTermMatrix error on Corpus argument

I&#39;ve got a subclass of UIViewController written in Swift called &#39;BaseViewController&#39;. I now have an &#39;old&#39; view controller called &#39;ViewController1&#39; written in Objective-C that I want to inherit from &#39;BaseViewController&#39;. Following other advice I have imported the &#39;Project-Swift.h&#39; header file.

My problem occurs when subclassing like this

    #import &lt;UIKit/UIKit.h&gt;
    #import &quot;MyProject-Swift.h&quot;

    @interface ViewController1 : BaseViewController
    @end

The error is:

Cannot subclass a class with objc_subclassing-restricted attribute

and it appears on the @interface ... line.



mixing objective-c and swift when subclassing

I've got a subclass of UIViewController written in Swift called 'BaseViewController'. I now have an 'old' view controller called 'ViewController1' written in Objective-C that I want to inherit from 'BaseViewController'. Following other advice I have imported the 'Project-Swift.h' header file.
My problem occurs when subclassing like this
<pre><code class="hljs language-objectivec">#import &#x3C;UIKit/UIKit.h>
#import "MyProject-Swift.h"

@interface ViewController1 : BaseViewController
@end
</code></pre>
The error is:
Cannot subclass a class with objc_subclassing-restricted attribute
and it appears on the @interface ... line.

I try to integrate `Swift` code in my app.My app is written in `Objective-C` and I added a `Swift` class. I&#39;ve done everything described [here](https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/BuildingCocoaApps/MixandMatch.html#//apple_ref/doc/uid/TP40014216-CH10-XID_77). But my problem is that `Xcode` haven&#39;t created the `-Swift.h` file, only the bridging headers. So I created it, but it&#39;s actually empty.
I can use all my ObjC classes in Swift, but I can&#39;t do it vice versa. I marked my swift class with `@objc` but it didn&#39;t help. What can I do now?

EDIT: Apple says:&quot; When you import Swift code into Objective-C, you rely on an `Xcode-generated` header file to expose those files to Objective-C. [...] The name of this header is your product module name followed by adding “-Swift.h”. &quot;

Now when I want to import that File, it gives an error:

        //MainMenu.m

        #import &quot;myProjectModule-Swift.h&quot; //Error: &#39;myProjectModule-Swift.h&#39; file not found
        
        @implementation MainMenu

Here is my FBManager.swift file:

    @objc class FBManager: NSObject {
        
        var descr = &quot;FBManager class&quot;
        
        init() {
            super.init()
        }
        
        func desc(){
            println(descr)
        }
        
        func getSharedGameState() -&gt; GameState{
            return GameState.sharedGameState() //OK! GameState is written in Objective-C and no error here
        }
    }



Can&#39;t use Swift classes inside Objective-C

I need to use swipe to recognize swipe gesture down and then right. But on swift UISwipeGestureRecognizer has predeterminate Right direction.. And I don&#39;t know how make this for use other directions..

How to recognize swipe in all 4 directions

With iOS 8.0, Apple introduced [UIAlertController](https://developer.apple.com/library/prerelease/iOS/documentation/UIKit/Reference/UIAlertController_class/index.html) to replace [UIActionSheet](https://developer.apple.com/library/ios/documentation/uikit/reference/uiactionsheet_class/Reference/Reference.html). Unfortunately, Apple didn&#39;t add any information on how to present it. I found an [entry](http://hayageek.com/uialertcontroller-example-ios/) about it on hayaGeek&#39;s blog, however, it doesn&#39;t seem to work on iPad. The view is totally misplaced:

Misplaced:
![Misplaced image][1]

Correct:
![enter image description here][2]


  [1]: http://i.stack.imgur.com/KhAaj.png
  [2]: http://i.stack.imgur.com/lFd3S.png

I use the following code to show it on the interface:

        let alert = UIAlertController()
        // setting buttons
        self.presentModalViewController(alert, animated: true)

Is there another way to add it for iPad? Or did Apple just forget the iPad, or not implemented, yet?

Presenting a UIAlertController properly on an iPad using iOS 8

In Obj-C I used to convert an unsigned integer n to a hex string with 

     NSString *st = [NSString stringWithFormat:@&quot;%2X&quot;, n];

I tried for a long time to translate this into Swift language, but unsuccessfully. 

How to convert an Int to Hex String in Swift

I&#39;d like to load an image from a URL in my application, so I first tried with Objective-C and it worked, however, with Swift, I&#39;ve a compilation error: 

&gt; &#39;imageWithData&#39; is unavailable: use object construction &#39;UIImage(data:)&#39;

My function: 

    @IBOutlet var imageView : UIImageView

    override func viewDidLoad() {
        super.viewDidLoad()
        
        var url:NSURL = NSURL.URLWithString(&quot;http://myURL/ios8.png&quot;)
        var data:NSData = NSData.dataWithContentsOfURL(url, options: nil, error: nil)

        imageView.image = UIImage.imageWithData(data)// Error here
    }

In Objective-C: 

    - (void)viewDidLoad {
        [super viewDidLoad];

        NSURL *url = [NSURL URLWithString:(@&quot;http://myURL/ios8.png&quot;)];
        NSData *data = [NSData dataWithContentsOfURL:url];
    
        _imageView.image = [UIImage imageWithData: data];
        _labelURL.text = @&quot;http://www.quentinroussat.fr/assets/img/iOS%20icon&#39;s%20Style/ios8.png&quot;;
     }

Can someone please explain me why the `imageWithData:` doesn&#39;t work with Swift, and how can I solve the problem. 

Loading/Downloading image from URL on Swift

Should I give my Swift class names a three-letter prefix as recommended by [Objective-C Conventions: Class Names Must Be Unique Across an Entire App][1]?

  [1]: https://developer.apple.com/library/ios/documentation/cocoa/conceptual/ProgrammingWithObjectiveC/Conventions/Conventions.html#//apple_ref/doc/uid/TP40011210-CH10-SW4

Swift: Class Prefix Needed?

How can I get the Device Token for remote notification in iOS 8?
I used the method `didRegisterForRemoteNotificationsWithDeviceToken` in `AppDelegate` in iOS &lt; 8, and it returned the device token. But in iOS 8, it does not.

Remote Notification iOS 8

if I declare the swift constant as a **global constant** like:

    let a = &quot;123&quot;


but the `a` cannot be found in **objective c**.

How to solve this?

How to declare a constant in swift that can be used in objective c

So this HTML code submits the data in the correct format for me.

	&lt;form action=&quot;https://www.example.com/register.php&quot; method=&quot;post&quot; enctype=&quot;multipart/form-data&quot;&gt;
		Name: &lt;input type=&quot;text&quot; name=&quot;userName&quot;&gt;&lt;BR /&gt;
		Email: &lt;input type=&quot;text&quot; name=&quot;userEmail&quot;&gt;&lt;BR /&gt;
		Password: &lt;input type=&quot;text&quot; name=&quot;userPassword&quot;&gt;&lt;BR /&gt;
		Avatar: &lt;input type=&quot;file&quot; name=&quot;avatar&quot;&gt;&lt;BR /&gt;
		&lt;input type=&quot;submit&quot;&gt;
	&lt;/form&gt;

I&#39;ve looked into a good number of articles on how to do a multipart/form-data POST on iOS, but none really explain what to do if there were normal parameters as well as the file upload.

Could you please help me with the code to POST this in Obj-C?

Thanks!

POST multipart/form-data with Objective-C

In a simple example like this, I can omit self for referencing backgroundLayer because it&#39;s unambiguous which backgroundLayer the backgroundColor is set on.

    class SpecialView: UIView {
        let backgroundLayer = CAShapeLayer()
        
        init() {
            backgroundLayer.backgroundColor = UIColor.greenColor().CGColor
        }
    }

But, just like in Objective-C, we can confuse things by adding local variables (or constants) named similarly. Now the backgroundColor is being set on the non-shape layer:

    class SpecialView: UIView {
        let backgroundLayer = CAShapeLayer()
        
        init() {
            var backgroundLayer = CALayer()

            backgroundLayer.backgroundColor = UIColor.greenColor().CGColor
        }
    }

(this is resolved by using self.backgroundLayer.backgroundColor)

In Objective-C I always eschewed ivars for properties and properties were always prefixed with self for clarity. I don&#39;t have to worry about ivars in swift but are there other considerations for when I should use self in swift?

When should I access properties with self in swift?

From Apple book
&quot;One of the most important differences between structures and classes is that structures are always copied when they are passed around in your code, but classes are passed by reference.&quot;

Can anyone help me understand what that means? To me, classes and structs seem to be the same.

Content Type	Original Author	Original Content on Stackoverflow
Question	apotry	View Question on Stackoverflow
Solution 1 - Ios	Anil Varghese	View Answer on Stackoverflow
Solution 2 - Ios	Lukas	View Answer on Stackoverflow
Solution 3 - Ios	steven yu	View Answer on Stackoverflow

mixing objective-c and swift when subclassing

Ios Problem Overview

Ios Solutions

Solution 1 - Ios

Solution 2 - Ios

Solution 3 - Ios

DocumentTermMatrix error on Corpus argument

How do I create a noop block for a switch case in Swift?

Attributions