Add the `-fobjc-arc` flag to any files for which you&#39;d like to enable ARC, as described in the [ARC documentation][1].


  [1]: http://clang.llvm.org/docs/AutomaticReferenceCounting.html#general

Select `Target &gt; Build Phases &gt;  Compile Source &gt; Select Your class &gt; Double Click `&gt; Type 

`-fobjc-arc` in dialog box 
[![enter image description here][1]][1]


  [1]: http://i.stack.imgur.com/q4cvT.png

Enter.

I have a list of numbers and I want to get the number of times a number appears in a list that meets a certain criteria. I can use a list comprehension (or a list comprehension in a function) but I am wondering if someone has a shorter way.

    # list of numbers
    j=[4,5,6,7,1,3,7,5]
    #list comprehension of values of j &gt; 5
    x = [i for i in j if i&gt;5]
    #value of x
    len(x)
    
    #or function version
    def length_of_list(list_of_numbers, number):
         x = [i for i in list_of_numbers if j &gt; number]
         return len(x)
    length_of_list(j, 5)

is there an even more condensed version?


number of values in a list greater than a certain number

With `String.Format()` it is possible to format for example `DateTime` objects in many different ways. Every time I am looking for a desired format I need to search around on Internet. Almost always I find an example I can use. For example:

    String.Format(&quot;{0:MM/dd/yyyy}&quot;, DateTime.Now);          // &quot;09/05/2012&quot;

But I don&#39;t have any clue how it works and which classes support these &#39;magic&#39; additional strings.  

So my questions are:

 1. How does `String.Format` map the additional information `MM/dd/yyyy` to a string result?
 2. Do all Microsoft objects support this feature?  
    Is this documented somewhere?
 3. Is it possible to do something like this:  
    `String.Format(&quot;{0:MyCustomFormat}&quot;, new MyOwnClass())`

String.Format - how it works and how to implement custom formatstrings

I want to bring a single Objective-C class written using ARC into an old project. The internet provides many references for how to enable ARC for your project and then disable it for single files but I want to do the opposite. 

I want to leave the project as it is, i.e. using manual reference counting, and then enable ARC just for the new file. (My searches have failed me here.)

Is this possible? How?

How to enable ARC for a single file

I want to bring a single Objective-C class written using ARC into an old project. The internet provides many references for how to enable ARC for your project and then disable it for single files but I want to do the opposite.
I want to leave the project as it is, i.e. using manual reference counting, and then enable ARC just for the new file. (My searches have failed me here.)
Is this possible? How?

When I insert new object I do with following code:

    NSManagedObjectContext *context = [appDelegate managedObjectContext];
                    
    Favorits *favorits = [NSEntityDescription insertNewObjectForEntityForName:@&quot;Favorits&quot; inManagedObjectContext:context];
                                 
    favorits.title = @&quot;Some title&quot;;
                                                
    NSError *error;                    
    if (![context save:&amp;error]) {
        NSLog(@&quot;Whoops&quot;);
    }

How can I update existing object in core data?

How to update existing object in Core Data?

How can I adjust the image size of the UIButton? I am setting the image like this:

    [myLikesButton setImage:[UIImage imageNamed:@&quot;icon-heart.png&quot;] forState:UIControlStateNormal];

However this fills up the image to the full button, how do I make the image smaller?

How to adjust an UIButton&#39;s imageSize?

For the past few weeks I&#39;ve been working with images in objective-c and noticing a lot of strange behavior.  First, like many other people, I&#39;ve been having this problem where images taken with the camera (or taken with somebody else&#39;s camera and MMS&#39;d to me) are rotated 90 degrees.  I wasn&#39;t sure why in the world this was happening (hence [my question][1]) but I was able to come up with a cheap work around.  

My question this time is **why is this happening**?  Why is Apple rotating images?  When I take a photo with my camera right-side up, unless I perform my code mentioned above, when I save the photo it gets saved rotated.  Now, my workaround was okay up until a few days ago.  

My application modifies individual pixels of an image, specifically the alpha channel of a PNG (so any JPEG conversion gets thrown out of the window for my scenario).  A few days ago I noticed that even though the image is displayed properly in my app thanks to my workaround code, when my algorithm modifies the individual pixels of the image, it thinks the image is rotated.  So instead of modifying the pixels at the top of the image, it modifies the pixels on the side of the image (because it thinks it should be rotated)!  I can&#39;t figure out how to rotate the image in memory - ideally I would prefer to just wipe away that `imageOrientation` flag all together.


Here&#39;s something else that has been baffling me as well... When I take the photo, the `imageOrientation` is set to 3.  My workaround code is smart enough to realize this and flip it so the user never notices.  Additionally, my code to save the image to the library realizes this, flips it, *then* saves it so it appears in the camera roll properly.  

That code looks like so:

    NSData* pngdata = UIImagePNGRepresentation (self.workingImage); //PNG wrap 
    UIImage* img = [self rotateImageAppropriately:[UIImage imageWithData:pngdata]];   
    UIImageWriteToSavedPhotosAlbum(img, nil, nil, nil);

When I load this newly saved image into my app, the `imageOrientation` is 0 - exactly what I want to see, and my rotation workaround doesn&#39;t even need to run (note: when loading images from the internet as opposed to images taken with a camera, the `imageOrientation` is always 0, resulting in perfect behavior).  For some reason, my save code seems to wipe away this `imageOrientation` flag.  I was hoping to just steal that code and use it to wipe away my imageOrientation as soon as the user takes a photo and has it added to the app, but it doesn&#39;t seem to work.  Does `UIImageWriteToSavedPhotosAlbum` do something special with `imageOrientation`?


Would the best fix for this problem  be to just blow away `imageOrientation` as soon as the user is done taking an image.  I assume Apple has the rotation behavior done for a reason, right?  A few people suggested that this is an Apple defect.  


(... if you&#39;re not lost yet... Note2:  When I take a horizontal photo, everything seems to work perfectly, just like photos taken from the internet)


EDIT:

Here are what some of the images and scenarios actually look like.  Based off the comments so far, it looks like this strange behavior is more than just an iPhone behavior, which I think is good.

This is a picture of the photo I took with my phone (note the proper orientation), it appears exactly as it did on my phone when I snapped the photo:

![Actual Photo taken on iPhone][2]

Here is what the image looks like in Gmail after I emailed it to myself (looks like Gmail handles it properly):

![Photo as it appears in Gmail][3]

Here is what the image looks like as a thumbnail in windows (doesn&#39;t look like it is handled properly):

![Windows Thumbnail][4]

And here is what the actual image looks like when opened with Windows Photo Viewer (still not handled properly):

![Windows Photo Viewer Version][5]

After all of the comments on this question, here&#39;s what I&#39;m thinking... The iPhone takes an image, and says &quot;to display this properly, it needs to be rotated 90 degrees&quot;.  This information would be in the EXIF data.  (Why it needs to be rotated 90 degrees, rather than defaulting to straight vertical, I don&#39;t know).  From here, Gmail is smart enough to read and analyze that EXIF data, and properly display it.  Windows however, is not smart enough to read the EXIF data, and therefore displays the image **improperly**.  Are my assumptions correct?


  [1]: https://stackoverflow.com/questions/10307521/ios-png-image-rotated-90-degrees &quot;my question&quot;
  [2]: http://i.stack.imgur.com/tG0Uf.png
  [3]: http://i.stack.imgur.com/pgIBL.png
  [4]: http://i.stack.imgur.com/S4rsI.png
  [5]: http://i.stack.imgur.com/SZKqC.png

iOS Image Orientation has Strange Behavior

I am making use of the `UIWebView` to render some HTML. However, although the width of my webview is 320 my HTML is still shown full width and can be scrolled horizontally.

I want to achieve the same thing the native mail application achieves which is it fits all content within that width without zooming out - how does the native mail application render HTML like this?

Update
---

I thought making use of the viewport meta tag will help, but I couldn&#39;t get this to work.

This is what is happening:

![enter image description here][1]


As you can see the content does not fit the device width. I&#39;ve tried so many combinations of `viewport` meta tag. The below is an example of what happens when I try Martins suggestion.

Original HTML is can be found [here][2].

The way this HTML is rendered by the [**native mail application is like so**][3].


  [1]: http://i.stack.imgur.com/Eei5Y.jpg
  [2]: http://dl.dropbox.com/u/50941418/2-build.html
  [3]: http://dl.dropbox.com/u/50941418/iphone_ex.PNG

HTML Content fit in UIWebview without zooming out

I want to create a clickable label on my app leading me to a Safari webpage. I also want the user to be able to phone the numbers only by clicking on them ? 

Thanks for your advices

How to make URL/Phone-clickable UILabel?

When not compiling with ARC, it is recommended to use `copy` properties for data types such as `NSString`. I could not find proper documentation on the use of `copy` in ARC mode. Can someone tell me what&#39;s applicable for ARC?  

Should an NSString property under ARC be strong or copy?

How can I avoid this warning in xcode. Here is the code snippet:

    [player(AVPlayer object) addPeriodicTimeObserverForInterval:CMTimeMakeWithSeconds(0.1, 100)
    queue:nil usingBlock:^(CMTime time) {
        current+=1;
                                                 
        if(current==60)
        {
            min+=(current/60);
            current = 0;
        }
        
        [timerDisp(UILabel) setText:[NSString stringWithFormat:@&quot;%02d:%02d&quot;,min,current]];///warning occurs in this line
    }];

capturing self strongly in this block is likely to lead to a retain cycle

I&#39;m trying to send an HTTP Post with the iOS application that I&#39;m developing but the push never reaches the server although I do get a code 200 as response (from the urlconnection). I never get a response from the server nor does the server detect my posts (the server does detect posts coming from android)

I do use ARC but have set pd and urlConnection as strong.

This is my code for sending the request

     NSMutableURLRequest *request = [[NSMutableURLRequest alloc]
                                        initWithURL:[NSURL URLWithString:[NSString stringWithFormat:@&quot;%@%@&quot;,dk.baseURL,@&quot;daantest&quot;]]];
        [request setHTTPMethod:@&quot;POST&quot;];
        [request setValue:@&quot;text/xml&quot;
       forHTTPHeaderField:@&quot;Content-type&quot;];
        
        NSString *sendString = @&quot;&lt;data&gt;&lt;item&gt;Item 1&lt;/item&gt;&lt;item&gt;Item 2&lt;/item&gt;&lt;/data&gt;&quot;;
        
        [request setValue:[NSString stringWithFormat:@&quot;%d&quot;, [sendString length]] forHTTPHeaderField:@&quot;Content-length&quot;];
        
        [request setHTTPBody:[sendString dataUsingEncoding:NSUTF8StringEncoding]];
        PushDelegate *pushd = [[PushDelegate alloc] init];
        pd = pushd;
        urlConnection = [[NSURLConnection alloc] initWithRequest:request delegate:pd];
        [urlConnection start];

this is my code for the delegate

    #import &quot;PushDelegate.h&quot;
    
    @implementation PushDelegate
    @synthesize data;
    
    -(id) init
    {
        if(self = [super init])
        {
            data = [[NSMutableData alloc]init];
            [data setLength:0];
        }
        return self;
    }
    
    
    - (void)connection:(NSURLConnection *)connection didWriteData:(long long)bytesWritten totalBytesWritten:(long long)totalBytesWritten
    {
        NSLog(@&quot;didwriteData push&quot;);
    }
    - (void)connectionDidResumeDownloading:(NSURLConnection *)connection totalBytesWritten:(long long)totalBytesWritten expectedTotalBytes:(long long)expectedTotalBytes
    {
        NSLog(@&quot;connectionDidResumeDownloading push&quot;);
    }
        
    - (void)connectionDidFinishDownloading:(NSURLConnection *)connection destinationURL:(NSURL *)destinationURL
    {
        NSLog(@&quot;didfinish push @push %@&quot;,data);
    }
    
    - (void)connection:(NSURLConnection *)connection didSendBodyData:(NSInteger)bytesWritten totalBytesWritten:(NSInteger)totalBytesWritten totalBytesExpectedToWrite:(NSInteger)totalBytesExpectedToWrite
    {
        NSLog(@&quot;did send body&quot;);
    }
    
    - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
    {
        [self.data setLength:0];
        NSHTTPURLResponse *resp= (NSHTTPURLResponse *) response;
        NSLog(@&quot;got response with status @push %d&quot;,[resp statusCode]);
    }
    
    - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)d
    {
        [self.data appendData:d];
        
        NSLog(@&quot;recieved data @push %@&quot;, data);
    }
    
    - (void)connectionDidFinishLoading:(NSURLConnection *)connection
    {
        NSString *responseText = [[NSString alloc] initWithData:self.data encoding:NSUTF8StringEncoding];
        
        NSLog(@&quot;didfinishLoading%@&quot;,responseText);
        
    }
    
    - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
    {
        [[[UIAlertView alloc] initWithTitle:NSLocalizedString(@&quot;Error &quot;, @&quot;&quot;)
                                    message:[error localizedDescription]
                                   delegate:nil
                          cancelButtonTitle:NSLocalizedString(@&quot;OK&quot;, @&quot;&quot;)
                          otherButtonTitles:nil] show];
        NSLog(@&quot;failed &amp;push&quot;);
    }
    
    // Handle basic authentication challenge if needed
    - (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge
    {
        NSLog(@&quot;credentials requested&quot;);
        NSString *username = @&quot;username&quot;;
        NSString *password = @&quot;password&quot;;
        
        NSURLCredential *credential = [NSURLCredential credentialWithUser:username
                                                                 password:password
                                                              persistence:NSURLCredentialPersistenceForSession];
        [[challenge sender] useCredential:credential forAuthenticationChallenge:challenge];
    }
    
    @end

The console always prints the following lines and the following lines only:

    2013-04-01 20:35:04.341 ApprenticeXM[3423:907] did send body
    2013-04-01 20:35:04.481 ApprenticeXM[3423:907] got response with status @push 200
    2013-04-01 20:35:04.484 ApprenticeXM[3423:907] didfinish push @push &lt;&gt;

Sending an HTTP POST request on iOS

I&#39;m using an `NSTimer` like this:

    timer = [NSTimer scheduledTimerWithTimeInterval:30.0f target:self selector:@selector(tick) userInfo:nil repeats:YES];

Of course, `NSTimer` retains the target which creates a retain cycle. Furthermore, `self` isn&#39;t a UIViewController so I don&#39;t have anything like `viewDidUnload` where I can invalidate the timer to break the cycle.  So I&#39;m wondering if I could use a weak reference instead:

    __weak id weakSelf = self;
    timer = [NSTimer scheduledTimerWithTimeInterval:30.0f target:weakSelf selector:@selector(tick) userInfo:nil repeats:YES];

I&#39;ve heard that the timer **must** be invalidated (i guess to release it from the run loop). But we could do that in our dealloc, right?

    - (void) dealloc {
        [timer invalidate];
    }

Is this a viable option? I&#39;ve seen a lot of ways that people deal with this issue, but I haven&#39;t seen this.

Weak Reference to NSTimer Target To Prevent Retain Cycle

I am trying to understand the correct way of getting an `NSString` from a `CFStringRef` in ARC?
Same for going the opposite direction, `CFStringRef` to `NSString` in ARC?

What is the correct way to do this without creating memory leaks?

Content Type	Original Author	Original Content on Stackoverflow
Question	Carlton Gibson	View Question on Stackoverflow
Solution 1 - Objective C	Caleb	View Answer on Stackoverflow
Solution 2 - Objective C	Alok	View Answer on Stackoverflow

How to enable ARC for a single file

Objective C Problem Overview

Objective C Solutions

Solution 1 - Objective C

Solution 2 - Objective C

String.Format - how it works and how to implement custom formatstrings

number of values in a list greater than a certain number

Attributions