**Swift v3:**

`let fileExists = FileManager.default.fileExists(atPath: somePath)`

Thanks to [Nikolay Suvandzhiev][1].

**Objective-C (Original):**

`BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:somePath];`


  [1]: https://stackoverflow.com/users/1678420/nikolay-suvandzhiev

I&#39;m developing a high-volume web application, where part of it is a MySQL database of discussion posts that will need to grow to 20M+ rows, smoothly.

I was originally planning on using MyISAM for the tables (for the built-in [fulltext search capabilities][1]), but the thought of the *entire table* being locked due to a single write operation makes me shutter. Row-level locks make so much more sense (not to mention InnoDB&#39;s other speed advantages when dealing with huge tables). So, for this reason, I&#39;m pretty determined to use InnoDB.

The problem is... InnoDB doesn&#39;t have built-in fulltext search capabilities.

Should I go with a third-party search system? Like [Lucene(c++)][2] / [Sphinx][3]? Do any of you database ninjas have any suggestions/guidance? &lt;del&gt;LinkedIn&#39;s [zoie][4] (based off Lucene) looks like the best option at the moment&lt;/del&gt;... having been built around realtime capabilities (which is pretty critical for my application.) I&#39;m a little hesitant to commit yet without some insight...

(FYI: going to be on EC2 with high-memory rigs, using PHP to serve the frontend)

  [1]: http://dev.mysql.com/doc/refman/5.1/en/fulltext-search.html
  [2]: http://sourceforge.net/projects/clucene/
  [3]: http://www.sphinxsearch.com/
  [4]: http://code.google.com/p/zoie/

Fulltext Search with InnoDB

As the title states, how can I display a tooltip message on hover using jQuery?


How can I display a tooltip message on hover using jQuery?

I want to quickly check to see if a file exists in my iPhone app&#39;s Documents directory (or any path for that matter).  I can enumerate through the directory&#39;s files, or I can try to open a specific file.  What&#39;s the fastest way?  I just need to know if the file is there or if it does not exist.


What&#39;s a quick way to test to see a file exists?

<p>I want to quickly check to see if a file exists in my iPhone app's Documents directory (or any path for that matter).  I can enumerate through the directory's files, or I can try to open a specific file.  What's the fastest way?  I just need to know if the file is there or if it does not exist.</p>


When I set up a table view with 4 rows, there are still extra separators lines (or extra blank cells) below the filled rows.

How would I remove these cells?

    
[![image for extra separator lines in UITableView][1]][1]


  [1]: http://i.stack.imgur.com/cFbz5.png

Eliminate extra separators below UITableView

I have a pointer to a `UIView`.  How do I access its `UIViewController`?  `[self superview]` is another `UIView`, but not the `UIViewController`, right?

Given a view, how do I get its viewController?

I have to ask this, because: The only thing I recognize is, that if the assertion fails, the app crashes. Is that the reason why to use NSAssert? Or what else is the benefit of it? And is it right to put an NSAssert just above any assumption I make in code, like a function that should never receive a -1 as param but may a -0.9 or -1.1?

What&#39;s the point of NSAssert, actually?

How can I create a basic `UIButton` programmatically? For example in my view controller, when executing the `viewDidLoad` method, three `UIButton`s will be created dynamically and its layout or properties are set.


How do I create a basic UIButton programmatically?

A 101 question

Let&#39;s say i&#39;m making database of cars
and each car object is defined as:

    #import &lt;UIKit/UIKit.h&gt;

    @interface Car:NSObject{
	    NSString *name;
    }

    @property(nonatomic, retain) NSString *name;

Why is it `@property(nonatomic, retain) NSString *name;` and not `@property(nonatomic, assign) NSString *name;`?

I understand that `assign` will not increment the reference counter as `retain` will do. But why use `retain`, since `name` is a member of the `todo` object the scope of it is to itself.

No other external function will modify it either.

Objective-C 101 (retain vs assign) NSString

I got this Base64 gif image:

    R0lGODlhDAAMALMBAP8AAP///wAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
    AAAAACH5BAUKAAEALAAAAAAMAAwAQAQZMMhJK7iY4p3nlZ8XgmNlnibXdVqolmhcRQA7

Now I want to display this Base64 String within my IPhone App.

I could get this working by using the WebView:
 

    aUIWebView.scalesPageToFit = NO;
    aUIWebView.opaque = NO;
    aUIWebView.backgroundColor = [UIColor clearColor]; 
    [aUIWebView loadHTMLString:
      @&quot;&lt;html&gt;&lt;body style=&quot;&quot;background-color: transparent&quot;&quot;&gt;&lt;img src=&quot;&quot;data:image/png;base64,R0lGODlhDAAMALMBAP8AAP///wAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAACH5BAUKAAEALAAAAAAMAAwAQAQZMMhJK7iY4p3nlZ8XgmNlnibXdVqolmhcRQA7&quot;&quot; /&gt;&lt;/body&gt;&lt;/html&gt;&quot;
     baseURL:nil];

Is it possible to do the same thing by using the UIImageView?


How to display a base64 image within a UIImageView?

I want to check the type of an Object. How can I do that?

The scenario is I&#39;m getting an object. If that object is of type A then do some operations. If it is of type B then do some operations. Currently the type of the object is C that is parent of A and B.

I have two classes `AViewController` and` BViewController`. The object I&#39;m getting in `UIViewController`. Now how to check whether the object is `AViewController` or `BViewController`?

iPhone how to check the type of an Object?

I get this cryptic error the first time (and only the first time) my view is loaded due to the following line of code:

    - (void)viewWillAppear:(BOOL)animated
    {
    	[textField becomeFirstResponder];
    }

There is a noticeable (~3 –&#160;4 second, even on the simulator) delay due to this that makes my app feel unresponsive. Does anyone know how to fix this? I can&#39;t find any documentation on it on Apple&#39;s site, or any solutions here or on Google.

Strangely, the opposite situation happens if I put the line in `-viewDidAppear:` instead of `-viewWillAppear:`; that is, instead of printing the error only the first time the keyboard is shown and never again, the error is _not_ printed the first time but every time after. This is causing a major headache for me.

&quot;wait_fences: failed to receive reply: 10004003&quot;?

By default there is a single line separator in uitableview.

But I want to put my customized line as a separator.

Is it possible? How?

How to customize tableView separator in iPhone

Currently the left bar button default value is the title of the view that loaded the current one, in other words the view to be shown when the button is pressed (back button).

I want to change the text shown on the button to something else.

I tried putting the following line of code in the view controller&#39;s viewDidLoad method but it doesn&#39;t seem to work.

    self.navigationItem.leftBarButtonItem.title = @&quot;Log Out&quot;;

What should I do?

Thanks.


How do I change the title of the &quot;back&quot; button on a Navigation Bar

I have an application with In-App Purchase, that when the user buy something, download one html file into the Documents folder of my app.

Now I must check if this HTML file exists, so if true, load this HTML file, else load my default html page.

How I can do that? With `NSFileManager` I can&#39;t get outside of `mainBundle`..


How to check if a file exists in Documents folder?

I just want to create new folders in the documents folder of my iPhone app.

Does anybody know how to do that?

Appreciate your help!

Create a folder inside documents folder in iOS apps

Snow Leopard introduced many new methods to use NSURL objects to refer to files, not pathnames or Core Services&#39; FSRefs.

However, there&#39;s one task I can&#39;t find a URL-based method for: Testing whether a file exists. I&#39;m looking for a URL-based version of [-\[NSFileManager `fileExistsAtPath:`\]](http://developer.apple.com/mac/library/documentation/Cocoa/Reference/Foundation/Classes/NSFileManager_Class/Reference/Reference.html#//apple_ref/occ/instm/NSFileManager/fileExistsAtPath:). Like that method, it should return `YES` if the URL describes anything, whether it&#39;s a regular file, a directory, or anything else.

I could attempt to look up various [resource values](http://developer.apple.com/mac/library/documentation/Cocoa/Reference/Foundation/Classes/NSURL_Class/Reference/Reference.html#//apple_ref/occ/instm/NSURL/resourceValuesForKeys:error:), but none of them are explicitly guaranteed to not exist if the file doesn&#39;t, and some of them (e.g., [NSURLEffectiveIconKey](http://developer.apple.com/mac/library/documentation/Cocoa/Reference/Foundation/Classes/NSURL_Class/Reference/Reference.html#//apple_ref/doc/c_ref/NSURLEffectiveIconKey)) could be costly if it does.

I could just use NSFileManager&#39;s `fileExistsAtPath:`, but if there&#39;s a more modern method, I&#39;d prefer to use that.

Is there a simple method or function in Cocoa, CF, or Core Services that&#39;s guaranteed/documented to tell me whether a given file (or file-reference) URL refers to a file-system object that exists?


Testing file existence using NSURL

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&#39;m looking for a better way to detect available/free disk space on the iPhone/iPad device programmatically.&lt;br&gt;
Currently I&#39;m using the NSFileManager to detect the disk space. Following is the snippet of the code which does the job for me:&lt;br&gt;

    -(unsigned)getFreeDiskspacePrivate {
    NSDictionary *atDict = [[NSFileManager defaultManager] attributesOfFileSystemForPath:@&quot;/&quot; error:NULL];
    unsigned freeSpace = [[atDict objectForKey:NSFileSystemFreeSize] unsignedIntValue];
    NSLog(@&quot;%s - Free Diskspace: %u bytes - %u MiB&quot;, __PRETTY_FUNCTION__, freeSpace, (freeSpace/1024)/1024);
    
    return freeSpace;
    }
&lt;br&gt;
Am I correct with the above snippet? or is there any better way to know total available/free disk space.&lt;br&gt;
I&#39;ve to detect total free disk space, since we&#39;ve to prevent our application to perform sync in the low disk space scenario.
&lt;br&gt;

How to detect total available/free disk space on the iPhone/iPad device?

I use `os.listdir` and it works fine, but I get sub-directories in the list also, which is not what I want: I need only files.

What function do I need to use for that?

I looked also at `os.walk` and it seems to be what I want, but I&#39;m not sure of how it works.


How to find files and skip directories in os.listdir

I am saving an image using saveImage.

    func saveImage (image: UIImage, path: String ) -&gt; Bool{
        
        let pngImageData = UIImagePNGRepresentation(image)
        //let jpgImageData = UIImageJPEGRepresentation(image, 1.0)   // if you want to save as JPEG

        print(&quot;!!!saving image at:  \(path)&quot;)

        let result = pngImageData!.writeToFile(path, atomically: true)
        
        return result
    }

New info:
-----------
Saving file does not work properly (&quot;[-] ERROR SAVING FILE&quot; is printed)--

                // save your image here into Document Directory
            let res = saveImage(tempImage, path: fileInDocumentsDirectory(&quot;abc.png&quot;))
            if(res == true){
                print (&quot;[+] FILE SAVED&quot;)
            }else{
                print (&quot;[-] ERROR SAVING FILE&quot;)
            }

Why doesn&#39;t the saveImage function save the image? Access rights? 

Older info:
-----------
The debug info says: 

    !!!saving image at:  file:///var/mobile/Applications/BDB992FB-E378-4719-B7B7-E9A364EEE54B/Documents/tempImage

Then I retrieve this location using

    fileInDocumentsDirectory(&quot;tempImage&quot;)

The result is correct. 

Then I am loading the file using this path

        let image = UIImage(contentsOfFile: path)
        
        if image == nil {
            
            print(&quot;missing image at: \(path)&quot;)
        }else{
            print(&quot;!!!IMAGE FOUND at: \(path)&quot;)
        }
        
The path is correct, but the message is &quot;missing image at..&quot;. Is the file somehow inaccessible or not stored? What can be a reason for this behavior?

I am testing this code on iphone 4 with ios 7 and iphone 5 with ios 7 simulator. 

Edit:
1. The fileInDocumentsDirectory function

    func fileInDocumentsDirectory(filename: String) -&gt; String {
 
        let documentsURL = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)[0]
        let fileURL = documentsURL.URLByAppendingPathComponent(filename).absoluteString
        return fileURL        
    }

            

Content Type	Original Author	Original Content on Stackoverflow
Question	mahboudz	View Question on Stackoverflow
Solution 1 - Ios	rein	View Answer on Stackoverflow

What's a quick way to test to see a file exists?

Ios Problem Overview

Ios Solutions

Solution 1 - Ios

How can I display a tooltip message on hover using jQuery?

Fulltext Search with InnoDB

Attributions