Use `[NSIndexPath indexPathForRow:inSection:]` to quickly create an index path.

**Edit:** In Swift 3:

    let indexPath = IndexPath(row: rowIndex, section: sectionIndex)

**Swift 5**

    IndexPath(row: 0, section: 0)

`indexPathForRow` is a class method!

The code should read:


    NSIndexPath *myIP = [NSIndexPath indexPathForRow:0 inSection:0] ;


Obligatory answer in Swift : `NSIndexPath(forRow:row, inSection: section)`  

You will notice that `NSIndexPath.indexPathForRow(row, inSection: section)` is not available in swift and you must use the first method to construct the indexPath.

For Swift 3 it&#39;s now: `IndexPath(row: rowIndex, section: sectionIndex)`

I noticed in `System.Threading.TimerBase.Dispose()` the method has a `try{} finally{}` block but the `try{}` is empty.

Is there any value in using `try{} finally{}` with an empty `try`?

http://labs.developerfusion.co.uk/SourceViewer/browse.aspx?assembly=SSCLI&amp;namespace=System.Threading&amp;type=TimerBase

    [ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
    internal bool Dispose(WaitHandle notifyObject)
    {
        bool status = false;
        bool bLockTaken = false;
        RuntimeHelpers.PrepareConstrainedRegions();
        try {
        }
        finally {
            do {
                if (Interlocked.CompareExchange(ref m_lock, 1, 0) == 0) {
                    bLockTaken = true;
                    try {
                        status = DeleteTimerNative(notifyObject.SafeWaitHandle);
                    }
                    finally {
                        m_lock = 0;
                    }
                }
                Thread.SpinWait(1);
                // yield to processor
            }
            while (!bLockTaken);
            GC.SuppressFinalize(this);
        }
       
        return status;
    }

Why use try {} finally {} with an empty try block?

How can I fire an event if a CSS class is added or changed using jQuery?
Does changing of a CSS class fire the jQuery `change()` event?

Firing events on CSS class changes in jQuery

I need delete row 1 of a table in a function I have defined. In order to use `deleteRowAtIndexPath` you must use an `IndexPath` with a section and row defined. How can I create an indexpath like this? 

An array with the int {1} as its only member will crash; the NSLog message states that the section needs to be defined as well. 

*Edit -&gt; Code relating to cell delete:

		NSIndexPath *myIP = [[NSIndexPath alloc] indexPathForRow:0 inSection:0];
		NSArray *myArray = [[NSArray alloc] initWithObjects:myIP, nil];
	//	[self.tableView beginUpdates];
		[self.tableView deleteRowsAtIndexPaths:myArray withRowAnimation:UITableViewRowAnimationFade];
	//	[self.tableView endUpdates];



How to create NSIndexPath for TableView

I need delete row 1 of a table in a function I have defined. In order to use <code>deleteRowAtIndexPath</code> you must use an <code>IndexPath</code> with a section and row defined. How can I create an indexpath like this?
An array with the int {1} as its only member will crash; the NSLog message states that the section needs to be defined as well.
*Edit -> Code relating to cell delete:
<pre><code class="hljs language-ini">	NSIndexPath *myIP = [[NSIndexPath alloc] indexPathForRow:0 inSection:0];
	NSArray *myArray = [[NSArray alloc] initWithObjects:myIP, nil];
//	[self.tableView beginUpdates];
	[self.tableView deleteRowsAtIndexPaths:myArray withRowAnimation:UITableViewRowAnimationFade];
//	[self.tableView endUpdates];
</code></pre>

When my app gets back to its root view controller, in the `viewDidAppear:` method I need to remove all subviews.

How can I do this?

How to remove all subviews?

I would like to add some rounded corners to all of the UIImageViews in my project. I have already got the code working, but am having to apply it to every image; should I subclass UIImageView to add this? If so, can someone give me some pointers as to how to do this?

Here is the code

    - (void)viewDidLoad {
        [super viewDidLoad];
    	NSString *mainpath = [[NSBundle mainBundle] bundlePath];
    	welcomeImageView.image = [UIImage imageWithContentsOfFile:[mainpath stringByAppendingString:@&quot;/test.png&quot;]];
    	welcomeImageView.layer.cornerRadius = 9.0;
    	welcomeImageView.layer.masksToBounds = YES;
    	welcomeImageView.layer.borderColor = [UIColor blackColor].CGColor;
    	welcomeImageView.layer.borderWidth = 3.0;
    	CGRect frame = welcomeImageView.frame;
    	frame.size.width = 100;
    	frame.size.height = 100;
    	welcomeImageView.frame = frame;
    }



Add rounded corners to all UIImageViews

I&#39;m creating a folder to cache images inside Documents with my iPhone App.  I want to be able to keep the size of this folder down to 1MB, so I need to to check the size in bytes of my folder.

I have code to calculate the [size of file](https://developer.apple.com/documentation/foundation/fileattributekey/1416548-size), but I need the size of the folder.

What would be the best way to do this?


How can I calculate the size of a folder?

I just need to ask something as follow.
Suppose I am having a dictionary.

	NSMutableDictionary *xyz=[[NSMutableDictionary alloc] init];
	[xyz setValue:@&quot;sagar&quot; forKey:@&quot;s&quot;];
	[xyz setValue:@&quot;amit&quot; forKey:@&quot;a&quot;];
	[xyz setValue:@&quot;nirav&quot; forKey:@&quot;n&quot;];
	[xyz setValue:@&quot;abhishek&quot; forKey:@&quot;a&quot;];
	[xyz setValue:@&quot;xrox&quot; forKey:@&quot;x&quot;];


Now, I need to check as follows

[xyz does contains key &quot;b&quot; value ?? pair or not?

Question is How? 

The other question is How to just count total key-value pair?

Say for example `NSInteger mCount=[xyz keyCounts];`


NSDictionary - Need to check whether dictionary contains key-value pair or not

I am attempting to send and receive messages through `NSNotificationCenter` in Objective-C. However, I haven&#39;t been able to find any examples on how to do this. How do you send and receive messages through `NSNotificationCenter`?

Send and receive messages through NSNotificationCenter in Objective-C?

From the official documentation:

&gt; The reuse identifier is associated with a UITableViewCell object that the table-view’s delegate creates with the intent to reuse it as the basis (for performance reasons) for multiple rows of a table view. It is assigned to the cell object in initWithFrame:reuseIdentifier: and cannot be changed thereafter. A UITableView object maintains a queue (or list) of the currently reusable cells, each with its own reuse identifier, and makes them available to the delegate in the dequeueReusableCellWithIdentifier: method.

http://developer.apple.com/iphone/library/documentation/UIKit/Reference/UITableViewCell_Class/Reference/Reference.html#//apple_ref/occ/instp/UITableViewCell/reuseIdentifier

I don&#39;t understand this. Well, I understand the basic idea, I think, that you create UITableViewCells, and try to reuse as many as you can instead of making new ones (or something like that). But what exactly decides whether or not a cell is reusable? If I&#39;ve got two identical (visually) cells, but with different texts (well I suppose they aren&#39;t entirely identical), can they both have the same identifier? Or should they have different ones? Or in what situation are you supposed to use different identifiers?

Can anyone clarify or link to a place where it is?

iPhone - What are reuseIdentifiers (UITableViewCell)?

I&#39;m using Instument&#39;s ObjectAlloc tool in an attempt to understand what the memory my application (iPhone) is doing and when and where it is doing it. 

I would really like a basic explanation of these statistics:

 - Live Bytes
 - #Living
 - #Transitory
 - Overall Bytes

When I am trying to work out how much memory my application is using, am I to look at Live Bytes or Overall Bytes? Does this include leaked memory? What are Transitory objects?

Thanks



Instruments ObjectAlloc: Explanation of Live Bytes &amp; Overall Bytes

I am having some problem in installing my app on the iphone as I am constantly getting the following error message

&gt; The service is invalid
&gt; 
&gt; Please check your setup and try again
&gt; 
&gt; (0XE8000022)

It was running perfectly well till yesterday but since yesterday I am having this problem.

Error : The service is invalid

I have installed [Google Toolbox for Mac][1] into Xcode and followed the instructions to set up unit testing found [here][2].

It all works great, and I can test my synchronous methods on all my objects absolutely fine.  However, most of the complex APIs I actually want to test return results asynchronously via calling a method on a delegate - for example a call to a file download and update system will return immediately and then run a -fileDownloadDidComplete: method when the file finishes downloading.

How would I test this as a unit test?   

It seems like I&#39;d want to the testDownload function, or at least the test framework to &#39;wait&#39; for fileDownloadDidComplete: method to run.


EDIT: I&#39;ve now switched to using the XCode built-in XCTest system and have found that [TVRSMonitor][3] on Github provides a dead easy way to use semaphores to wait for async operations to complete. 

For example:

    - (void)testLogin {
      TRVSMonitor *monitor = [TRVSMonitor monitor];
      __block NSString *theToken;

      [[Server instance] loginWithUsername:@&quot;foo&quot; password:@&quot;bar&quot;
                                   success:^(NSString *token) {
                                       theToken = token;
                                       [monitor signal];
                                   }

                                   failure:^(NSError *error) {
                                       [monitor signal];
                                   }];

      [monitor wait];

      XCTAssert(theToken, @&quot;Getting token&quot;);
    }


  [1]: http://code.google.com/p/google-toolbox-for-mac/
  [2]: http://code.google.com/p/google-toolbox-for-mac/wiki/iPhoneUnitTesting
  [3]: https://github.com/travisjeffery/TRVSMonitor

How to unit test asynchronous APIs?

Is there any way to test the iPhone camera in the simulator without having to deploy on a device? This seems awfully tedious.

How do I test a camera in the iPhone simulator?

Case
----------
Normally you would use the `cellForRowAtIndexPath` delegate method to setup your cell. The information set for the cell is important for how the cell is drawn and what the size will be.

Unfortunatly the `heightForRowAtIndexPath` delegate method is called before the `cellForRowAtIndexPath` delegate method so we can&#39;t simply tell the delegate to return the height of the cell, since this will be zero at that time.

So we need to calculate the size before the cell is drawn in the table. Luckily there is a method that does just that, `sizeWithFont`, which belongs to the NSString class. However there is problem, in order to calculate the correct size dynamically it needs to know how the elements in the cell will be presented. I will make this clear in an example:

Imagine a `UITableViewCell`, which contains a label named `textLabel`. Within the `cellForRowAtIndexPath` delegate method we place `textLabel.numberOfLines = 0`, which basically tells the label it can have as many lines as it needs to present the text for a specific width. The problem occurs if we give textLabel a text larger then the width originally given to textLabel. The second line will appear, but the height of the cell will not be automatically adjusted and so we get a messed up looking table view.

As said earlier, we can use `sizeWithFont` to calculate the height, but it needs to know which Font is used, for what width, etc. If, for simplicity reasons, we just care about the width, we could hardcode that the width would be around 320.0 (not taking padding in consideration). But what would happen if we used UITableViewStyleGrouped instead of plain the width would then be around 300.0 and the cell would again be messed up. Or what happends if we swap from portrait to landscape, we have much more space, yet it won&#39;t be used since we hardcoded 300.0.

This is the case in which at some point you have to ask yourself the question how much can you avoid hardcoding.


My Own Thoughts
----------
You could call the `cellForRowAtIndexPath` method that belongs to the UITableView class to get the cell for a certain section and row. I read a couple of posts that said you don&#39;t want to do that, but I don&#39;t really understand that. Yes, I agree it will already allocate the cell, but the `heightForRowAtIndexPath` delegate method is only called for the cells that will be visible so the cell will be allocated anyway. If you properly use the `dequeueReusableCellWithIdentifier` the cell will not be allocated again in the `cellForRowAtIndexPath` method, instead a pointer is used and the properties are just adjusted. Then what&#39;s the problem? 

Note that the cell is NOT drawn within the `cellForRowAtIndexPath` delegate method, when the table view cell becomes visible the script will call the `setNeedDisplay` method on the UITableVieCell which triggers the `drawRect` method to draw the cell. So calling the `cellForRowAtIndexPath` delegate directly will not lose performance because it needs to be drawn twice.

Okay so by calling the `cellForRowAtIndexPath` delegate method within the `heightForRowAtIndexPath` delegate method we receive all the information we need about the cell to determine it&#39;s size. 

Perhaps you can create your own `sizeForCell` method that runs through all the options, what if the cell is in Value1 style, or Value2, etc.

Conclusion/Question
----------
It&#39;s just a theory I described in my thoughts, I would like to know if what I wrote is correct. Or that maybe there is another way to accomplish the same thing. Note that I want to be able to do things as flexible as possible.

UITableView flexible/dynamic heightForRowAtIndexPath

I&#39;ve been creating a list app and backing it with core data.

I would like to have a default list of say 10 airport&#39;s items, so that the user doesn&#39;t have to start from scratch.

Is there any way to do this? 

Any help is appreciated. 
Thanks in advance.

Any way to pre populate core data?

I am displaying in a group `tableview` contents parsed from XML. I want to disable the click event on it (I should not be able to click it at all) The table contains two groups. I want to disable selection for the first group only but not the second group. Clicking the first row of second group `navigates` to my tube `player view`. 

How can I make just specific groups or rows selectable?

    - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath 
    {
	    if(indexPath.section!=0)
	    if(indexPath.row==0)	
		
	    [[UIApplication sharedApplication] openURL:[NSURL URLWithString:tubeUrl]]; 	 
    }




Thanks.

UITableview: How to Disable Selection for Some Rows but Not Others

I have a UITableView where when I put it in editing mode, I want selective rows to be selectable, however, they are not. Is there a way I can force them to be selectable?

Selecting row while UITableView is in editing mode

How can I get a `UITableViewCell` by `indexPath`? Like this:

I use the `UIActionSheet`, when I click confirm `UIButton` I want to change the cell text.

The nowIndex I define as a property

    - (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex
    {
        if (buttonIndex == 0)
        {
            NSInteger section =  [nowIndex section];
            NSInteger row = [nowIndex row];
            NSDateFormatter *formatter = [[[NSDateFormatter alloc] init] autorelease];
            formatter.dateFormat = @&quot;yyyy-MM-dd&quot;;
     
            if (section == 0)
            {
                if (row == 0)
                {
        
                }
                else if (row == 1)
                {
                    UILabel *content = (UILabel *)[[(UITableView *)[actionSheet ] cellForRowAtIndexPath:nowIndex] viewWithTag:contentTag];
                    content.text = [formatter stringFromDate:checkInDate.date];
                }
                else if (row == 2)
                {
        
                }
            }
        }
    }

How can I get a uitableViewCell by indexPath?

I want to have selected index for `UITableView`.
I have written following code:


    NSIndexPath *index = [NSIndexPath indexPathForRow:1 inSection:0];
    [tableView scrollToRowAtIndexPath:index 
                     atScrollPosition:UITableViewScrollPositionTop 
                             animated:YES];

This always work for 1st item. I want to have selected index in `indexPathForRow.`

Please help.
Thanks.


Get Selected index of UITableView

&lt;p&gt;I have encountered a really puzzling bug. The &lt;strong&gt;first&lt;/strong&gt; row of my UITableView returns &lt;b&gt;1&lt;/b&gt; and the &lt;b&gt;second&lt;/b&gt; one returns &lt;b&gt;0&lt;/b&gt; in the indexPath! How is that even possible?&lt;/p&gt;

&lt;p&gt;In my `-(void)viewDidLoad` everything is still fine. I am highlighting the first row successfully with &lt;/p&gt;
    currentRow = 0;
    [tableView selectRowAtIndexPath:[NSIndexPath indexPathForRow:currentRow inSection:0] 
      animated:NO scrollPosition:UITableViewScrollPositionNone];
I have the variable `currentRow` for tracking which row is selected (another control changes according to which one is currently selected).

&lt;p&gt;Now in my `didDeselectRowAtIndexPath` delegate function I have:&lt;/p&gt;
    -(void)tableView:(UITableView *)tableView didDeselectRowAtIndexPath:(NSIndexPath *)indexPath {
    ...
    NSLog(@&quot;IndexPath: %@&quot;, [indexPath description]);
    }

The log shows the following:

`IndexPath: &lt;NSIndexPath 0x79509d0&gt; 2 indexes [0, 0]` when I touch the &lt;i&gt;second&lt;/i&gt; row, and
`IndexPath: &lt;NSIndexPath 0x79509d0&gt; 2 indexes [0, 1]` when I touch the &lt;i&gt;first&lt;/i&gt; row.

There are is no row insertion or deletion or sorting, etc., not even scrolling. It is a simple UITableView, grouped style, with 1 section and 3 rows. What could be causing this?

Thanks for your help,&lt;br&gt;
S

didSelectRowAtIndexPath returns wrong IndexPath

Does anyone know the difference between `NSIndexpath.row` and `NSIndexpath.item`? 

Specifically, which one do I use in:

    -(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath;



NSIndexpath.item vs NSIndexpath.row

I am a beginning developer in Swift, and I am creating a basic app that includes a UITableView. I want to refresh a certain row of the table using:

    self.tableView.reloadRowsAtIndexPaths(paths, withRowAnimation: UITableViewRowAnimation.none)

and I want the row that will be refreshed to be from an Int named rowNumber

The problem is, I don&#39;t know how to do this and all the threads I&#39;ve searched are for Obj-C

Any ideas?

Content Type	Original Author	Original Content on Stackoverflow
Question	Rubber Duck	View Question on Stackoverflow
Solution 1 - Ios	Ben Gottlieb	View Answer on Stackoverflow
Solution 2 - Ios	verec	View Answer on Stackoverflow
Solution 3 - Ios	JohnVanDijk	View Answer on Stackoverflow
Solution 4 - Ios	comrade	View Answer on Stackoverflow

How to create NSIndexPath for TableView

Ios Problem Overview

Ios Solutions

Solution 1 - Ios

Solution 2 - Ios

Solution 3 - Ios

Solution 4 - Ios

Firing events on CSS class changes in jQuery

Why use try {} finally {} with an empty try block?

Attributions