Looks fine to me. This is what I use (available as a [gist][1])

    - (NSString *)uuidString {
        // Returns a UUID
        
        CFUUIDRef uuid = CFUUIDCreate(kCFAllocatorDefault);
        NSString *uuidString = (__bridge_transfer NSString *)CFUUIDCreateString(kCFAllocatorDefault, uuid);
        CFRelease(uuid);
        
        return uuidString;
    }

**Edited to add**

If you are on OS X 10.8 or iOS 6 you can use the new [NSUUID](http://developer.apple.com/library/mac/#documentation/Foundation/Reference/NSUUID_Class/Reference/Reference.html) class to generate a string UUID, without having to go to Core Foundation:

    NSString *uuidString = [[NSUUID UUID] UUIDString];
    // Generates: 7E60066C-C7F3-438A-95B1-DDE8634E1072

But mostly, if you just want to generate a unique string for a file or directory name then you can use `NSProcessInfo`&#39;s `globallyUniqueString` method like:

    NSString *uuidString = [[NSProcessInfo processInfo] globallyUniqueString];
    // generates 56341C6E-35A7-4C97-9C5E-7AC79673EAB2-539-000001F95B327819

It&#39;s not a formal UUID, but it is unique for your network and your process and is a good choice for a lot of cases.

  [1]: https://gist.github.com/1501325

That looks correct to me.

You have CFRelease&#39;d `uuid`, which is your responsibility from the `CFUUIDCreate()`

And you&#39;ve transferred ownership of the string to ARC, so the compiler knows to release `uuidStr` at the appropriate time.


From [clang docs](http://clang.llvm.org/docs/AutomaticReferenceCounting.html#objects.operands.casts):

&gt; *`(__bridge_transfer T)`* op casts the operand, which must have non-retainable pointer type, to the destination type, which must be a retainable object pointer type. ARC will release the value at the end of the enclosing full-expression, subject to the usual optimizations on local values.

So you are doing it right.

I&#39;ve created a `JOptionPane` and it only has two buttons `YES_NO_OPTION` .

After `JOptionPane.showConfirmDialog` pops out , I want to click `YES BUTTON` to continue opening the `JFileChooser` and if I clicked `NO BUTTON` it should cancel the operation.

It seems pretty easy but I&#39;m not sure where is my mistake.

Code Snippet:

    if (textArea.getLineCount() &gt;= 1) {  //The condition to show the dialog if there is text inside the textArea

        int dialogButton = JOptionPane.YES_NO_OPTION;
        JOptionPane.showConfirmDialog (null, &quot;Would You Like to Save your Previous Note First?&quot;,&quot;Warning&quot;,dialogButton);
    
        if (dialogButton == JOptionPane.YES_OPTION) { //The ISSUE is here
    					
        JFileChooser saveFile = new JFileChooser();
        int saveOption = saveFile.showSaveDialog(frame);
        if(saveOption == JFileChooser.APPROVE_OPTION) {
    
        try {
        	BufferedWriter fileWriter = new BufferedWriter(new FileWriter(saveFile.getSelectedFile().getPath()));
        	fileWriter.write(textArea.getText());
        	fileWriter.close();
        } catch(Exception ex) {
    
        }
    }

JOptionPane YES/No Options Confirm Dialog Box Issue

I&#39;m  using a jQuery modal dialog in my ASP .NET MVC 3 application. It works fine except for that there is no close button showing in the top right corner. How can I add this?

    $(&quot;#dialog-modal&quot;).dialog({
                modal: true,
                autoOpen: false,
                buttons: {
                    Ok: function () {
                        $(this).dialog(&quot;close&quot;);
                    }
                }
            });

jQueryUI modal dialog does not show close button (x)

I need to generate a UUID string in some code with ARC enabled.

After doing some research, this is what I came up with:

    CFUUIDRef uuid = CFUUIDCreate(NULL);
    NSString *uuidStr = (__bridge_transfer NSString *)CFUUIDCreateString(NULL, uuid);
    CFRelease(uuid);

Am I correctly using `__bridge_transfer` to avoid leaking any objects under ARC?

Generate a UUID string with ARC enabled

I need to generate a UUID string in some code with ARC enabled.
After doing some research, this is what I came up with:
<pre><code class="hljs language-objectivec">CFUUIDRef uuid = CFUUIDCreate(NULL);
NSString *uuidStr = (__bridge_transfer NSString *)CFUUIDCreateString(NULL, uuid);
CFRelease(uuid);
</code></pre>
Am I correctly using <code>__bridge_transfer</code> to avoid leaking any objects under ARC?

I referred to the [DOC](http://developer.apple.com/library/IOs/#documentation/UIKit/Reference/UIView_Class/UIView/UIView.html#//apple_ref/occ/clm/UIView/animateWithDuration:animations:) and it said:
&gt; __completion__  
&gt; ... This block has no return value and takes a single Boolean argument that indicates whether or not the animations actually finished before the completion handler was called. ...

But I find that no matter you use the bool parameter or not, the `completion:` block will always execute after `animations:` block. Just like the two simple block-based animation code snippets shown below, both of them are doing the same.

    [UIView animateWithDuration:0.3f
                      delay:0.0f
                    options:UIViewAnimationCurveEaseInOut
                 animations:^{
                     [myView setAlpha:0.0f];
                 }
                 completion:^(BOOL finished) {
                     [myView removeFromSuperview];
                 }];
and

    [UIView animateWithDuration:0.3f
                      delay:0.0f
                    options:UIViewAnimationCurveEaseInOut
                 animations:^{
                     [myView setAlpha:0.0f];
                 }
                 completion:^(BOOL finished) {
                     if (finished) [myView removeFromSuperview];
                 }];

And I find that most people(including me) use the first one(even the apple&#39;s official doc example). So,

- what&#39;s the `finished` parameter used for here exactly?
- or what&#39;s the situation will be used?

What exactly does bool parameter do in animateWithDuration:animations:completion:

I have a textfield in my iOS app where the user is supposed to input some text. But I was wondering if there is any way to convert the users input to lowercase letters.

I remember in C# it was something like `Convert.ToLower` but I can&#39;t seem to figure out how to do it in Objective-C.

Converting all text to lower case in Objective-C

How do you smooth a set of points in an iOS drawing app WHILE MOVING? I have tried UIBezierpaths but all I get are jagged ends where they intersect, when I just shift the points 1,2,3,4 - 2,3,4,5. I have heard of spline curves and all the other types. I am quite new to iPhone programming and do not understand how to program it in my quartz drawing app. A solid example would be greatly appreciated, I have spent weeks running in circles and I can never seem to find any iOS code for this task. Most of the posts just link to a java simulation or pages on wikipedia about curve fitting which does nothing for me. Also I do not want to switch to openGL ES. I hope someone can finally provide code to answer this circulating question.

---

This was my code for the UIBezierPath which left edges at intersection///

UPDATED TO AN ANSWER BELOW

    #define VALUE(_INDEX_) [NSValue valueWithCGPoint:points[_INDEX_]]
    #define POINT(_INDEX_) [(NSValue *)[points objectAtIndex:_INDEX_] CGPointValue]

    - (UIBezierPath*)smoothedPathWithGranularity:(NSInteger)granularity
    {
        NSMutableArray *points = [(NSMutableArray*)[self pointsOrdered] mutableCopy];
        
        if (points.count &lt; 4) return [self bezierPath];
        
        // Add control points to make the math make sense
        [points insertObject:[points objectAtIndex:0] atIndex:0];
        [points addObject:[points lastObject]];
        
        UIBezierPath *smoothedPath = [self bezierPath];
        [smoothedPath removeAllPoints];
        
        [smoothedPath moveToPoint:POINT(0)];
        
        for (NSUInteger index = 1; index &lt; points.count - 2; index++)
        {
            CGPoint p0 = POINT(index - 1);
            CGPoint p1 = POINT(index);
            CGPoint p2 = POINT(index + 1);
            CGPoint p3 = POINT(index + 2);
            
            // now add n points starting at p1 + dx/dy up until p2 using Catmull-Rom splines
            for (int i = 1; i &lt; granularity; i++)
            {
                float t = (float) i * (1.0f / (float) granularity);
                float tt = t * t;
                float ttt = tt * t;
                
                CGPoint pi; // intermediate point
                pi.x = 0.5 * (2*p1.x+(p2.x-p0.x)*t + (2*p0.x-5*p1.x+4*p2.x-p3.x)*tt + (3*p1.x-p0.x-3*p2.x+p3.x)*ttt);
                pi.y = 0.5 * (2*p1.y+(p2.y-p0.y)*t + (2*p0.y-5*p1.y+4*p2.y-p3.y)*tt + (3*p1.y-p0.y-3*p2.y+p3.y)*ttt);
                [smoothedPath addLineToPoint:pi];
            }
            
            // Now add p2
            [smoothedPath addLineToPoint:p2];
        }
        
        // finish by adding the last point
        [smoothedPath addLineToPoint:POINT(points.count - 1)];
        
        return smoothedPath;
    }
    - (PVPoint *)pointAppendingCGPoint:(CGPoint)CGPoint
    {
        PVPoint *newPoint = [[PVPoint alloc] initInsertingIntoManagedObjectContext:[self managedObjectContext]];
        [newPoint setCGPoint:CGPoint];
        [newPoint setOrder:[NSNumber numberWithUnsignedInteger:[[self points] count]]];
        [[self mutableSetValueForKey:@&quot;points&quot;] addObject:newPoint];
        [(NSMutableArray *)[self pointsOrdered] addObject:newPoint];
        [[self bezierPath] addLineToPoint:CGPoint];
        return [newPoint autorelease];
        
        if ([self bezierPath] &amp;&amp; [pointsOrdered count] &gt; 3)
        {
            PVPoint *control1 = [pointsOrdered objectAtIndex:[pointsOrdered count] - 2];
            PVPoint *control2 = [pointsOrdered objectAtIndex:[pointsOrdered count] - 1];
            [bezierPath moveToPoint:[[pointsOrdered objectAtIndex:[pointsOrdered count] - 3] CGPoint]];
            [[self bezierPath] addCurveToPoint:CGPoint controlPoint1:[control1 CGPoint] controlPoint2:[control2 CGPoint]];
            
        }
        
    }

    - (BOOL)isComplete { return [[self points] count] &gt; 1; }

    - (UIBezierPath *)bezierPath
    {
        if (!bezierPath)
        {
            bezierPath = [UIBezierPath bezierPath];
            for (NSUInteger p = 0; p &lt; [[self points] count]; p++)
            {
                if (!p) [bezierPath moveToPoint:[(PVPoint *)[[self pointsOrdered] objectAtIndex:p] CGPoint]];
                else [bezierPath addLineToPoint:[(PVPoint *)[[self pointsOrdered] objectAtIndex:p] CGPoint]];
            }
            [bezierPath retain];
        }
        
        return bezierPath;
    }

    - (CGPathRef)CGPath
    {
        return [[self bezierPath] CGPath];
    }


![phone screen][1]


  [1]: http://i.stack.imgur.com/hS7wY.png

Drawing Smooth Curves - Methods Needed

Where can I find information on how to modify these 

- `${EXECUTABLE_NAME}`
- `${PRODUCT_NAME}`

These are only displayed in .plist file but where are the actual values.

If we can directly modify what ever we want in .plist why we need these.

I am new that&#39;s why I&#39;m having problem understanding these, I also looked into apple information Property list key reference but didn&#39;t find these ${} values.


Where are ${EXECUTABLE_NAME} and ${PRODUCT_NAME} defined

As I cannot create a synthesized property in a Category in Objective-C, I do not know how to optimize the following code:

    @interface MyClass (Variant)
    @property (nonatomic, strong) NSString *test;
    @end

    @implementation MyClass (Variant)

    @dynamic test;

    - (NSString *)test {
        NSString *res;
        //do a lot of stuff
        return res;
    }

    @end

The *test-method* is called multiple times on runtime and I&#39;m doing a lot of stuff to calculate the result. Normally using a synthesized property I store the value in a IVar _test the first time the method is called, and just returning this IVar next time. How can I optimized the above code?

Objective-C: Property / instance variable in category

I&#39;ve yet to use ARC, since the majority of the code in the project I&#39;m working on at the moment was written pre-iOS 5.0. 

I was just wondering, does the convenience of not retaining/releasing manually (and presumably more reliable code that comes as a result?) outweigh any &#39;cost&#39; of using ARC?
What are your experiences of ARC, and would you recommend it?

So:

 - How much benefit can ARC bring to a project?
 - Does ARC have a cost like garbage collection in Java?
 - Have you been using ARC and if so, how have you found it so far?


To ARC or not to ARC? What are the pros and cons?

I&#39;m trying to complete the puzzle.

`__strong` is the default for all Objective-C retainable object pointers like NSObject, NSString, etc.. It&#39;s a strong reference. ARC balances it with a `-release` at the end of the scope.

`__unsafe_unretained` equals the old way. It&#39;s used for a weak pointer without retaining the retainable object.

`__weak` is like `__unsafe_unretained` except that it&#39;s an auto-zeroing weak reference meaning that the pointer will be set to nil as soon as the referenced object is deallocated. This eliminates the danger of dangling pointers and EXC_BAD_ACCESS errors.

But what exactly is `__autoreleasing` good for? I&#39;m having a hard time finding practical examples on when I need to use this qualifier. I believe it&#39;s only for functions and methods which expect a pointer-pointer such as:

    - (BOOL)save:(NSError**);

or

    NSError *error = nil;
    [database save:&amp;error];

which under ARC has to be declared this way:

    - (BOOL)save:(NSError* __autoreleasing *);

But this is too vague and I&#39;d like to fully understand *why*. The code snippets I find place the __autoreleasing inbetween the two stars, which looks weird to me. The type is `NSError**` (a pointer-pointer to NSError), so why place `__autoreleasing` inbetween the stars and not simply in front of `NSError**`? 

Also, there might be other situations in which I must rely on `__autoreleasing`.

In which situations do we need to write the __autoreleasing ownership qualifier under ARC?

I assure you that I did look for an answer in SO for my question but none of them were helpful. Here I got a simple code that should present a `UIImagePickerController` within a `UIPopoverController`:
   
    -(void)takePicture:(id)sender{
    UIImagePickerController *picker=[[UIImagePickerController alloc] init];
    picker.delegate=self;
    picker.sourceType=UIImagePickerControllerSourceTypeCamera;
    picker.allowsEditing=YES;
    UIPopoverController *poc=[[UIPopoverController alloc] 
                                initWithContentViewController:picker];
    [poc presentPopoverFromBarButtonItem:bbItem 
                permittedArrowDirections:UIPopoverArrowDirectionAny
                                animated:NO];
    }

Now, even from the first time I get `[UIPopoveController dealloc]` reached while... error and the program crashes. I&#39;m not doing any retain,relase or autoreleases as per ARC. Is there any special consideration with `UIPopoverControllers` when benefitting from ARC?

UIPopovercontroller dealloc reached while popover is still visible

There are two new memory management attributes for properties introduced by ARC, `strong` and `weak`.

Apart from `copy`, which is obviously something completely different, **are there any differences between `strong` vs `retain` and `weak` vs `assign`?**

From my understanding, the only difference here is that `weak` will assign `nil` to the pointer, while `assign` won&#39;t, which means the program will crash when I send a message to the pointer once it&#39;s been released. But if I use `weak`, this won&#39;t ever happen, because message send to `nil` won&#39;t do anything.

I don&#39;t know about any differences between `strong` and `retain`.

**Is there any reason why should I use `assign` and `retain` in new projects, or are the kind of being deprecated?**

Objective-C ARC: strong vs retain and weak vs assign

If a project has already been created with ARC disabled, how do I enable it and vice versa?

Content Type	Original Author	Original Content on Stackoverflow
Question	Abhi Beckert	View Question on Stackoverflow
Solution 1 - Objective C	Abizern	View Answer on Stackoverflow
Solution 2 - Objective C	Firoze Lafeer	View Answer on Stackoverflow
Solution 3 - Objective C	iHunter	View Answer on Stackoverflow

Generate a UUID string with ARC enabled

Objective C Problem Overview

Objective C Solutions

Solution 1 - Objective C

Solution 2 - Objective C

Solution 3 - Objective C

jQueryUI modal dialog does not show close button (x)

JOptionPane YES/No Options Confirm Dialog Box Issue

Attributions