There are many ways to do it, the simplest being

    [yourArray componentsJoinedByString: @&quot;,&quot;]

Use NSArray&#39;s `componentsJoinedByString:` method.

    NSArray *strings = ...;
    NSString *combined = [strings componentsJoinedByString:@&quot;,&quot;];

Please explain why this test passes?

    [Test]
    public void TestNullOps()
    {
        Assert.That(10 / null, Is.Null);
        Assert.That(10 * null, Is.Null);
        Assert.That(10 + null, Is.Null);
        Assert.That(10 - null, Is.Null);
        Assert.That(10 % null, Is.Null);
        Assert.That(null / 10, Is.Null);
        Assert.That(null * 10, Is.Null);
        Assert.That(null + 10, Is.Null);
        Assert.That(null - 10, Is.Null);
        Assert.That(null % 10, Is.Null);

        int zero = 0;
        Assert.That(null / zero, Is.Null);
    }

I don&#39;t understand how this code even compiles.

Looks like each math expression with null returns `Nullable&lt;T&gt;` (e.g. `10 / null` is a `Nullable&lt;int&gt;`). But I don&#39;t see operator methods in `Nullable&lt;T&gt;` class. If these operators are taken from `int`, why the last assertion doesn&#39;t fail?


Math operations with null

I&#39;m dynamically generating `config.mk` with a bash script which will be used by a Makefile. The file is constructed with:

    cat &gt; config.mk &lt;&lt;CFG
    SOMEVAR := $value_from_bash1
    ANOTHER := $value_from_bash2
    CFG
How do I ensure that the generated file really contains the contents of `$value_from_bash*`, and not something expanded / interpreted? I probably need to escape `$` to `$$` and `\` to `\\`, but are there other characters that needs to be escaped? Perhaps there is a special literal assignment I&#39;ve not heard of?

Spaces seems to be troublesome too:

    $ ls -1
    a b
    a
    $ cat Makefile
    f := a b
    default_target:
        echo &quot;$(firstword $(wildcard ${f}))&quot;
    $ make
    a
If I use `f := a\ b` it works (using quotes like `f := &#39;a b&#39;` did not work either, makefile just treats it as a regular character)

How do I properly escape data for a Makefile?

I am an Objective C newbie. I want to write a method that takes in an array of strings and returns a concatenated string, with a comma (,) in between each string. 
So if an array is {a b c d}, I want to return a,b,c,d.

What is the easiest way to do that?



Objective C - How to concatenate an entire array of strings?

<p>I am an Objective C newbie. I want to write a method that takes in an array of strings and returns a concatenated string, with a comma (,) in between each string.
So if an array is {a b c d}, I want to return a,b,c,d.</p>
<p>What is the easiest way to do that?</p>


I am developing exclusively for iOS 5 using ARC. Should `IBOutlet`s to `UIView`s (and subclasses) be `strong` or `weak`?

The following:

    @property (nonatomic, weak) IBOutlet UIButton *button;

Would get rid of all of this:

    - (void)viewDidUnload
    {
        // ...
        self.button = nil;
        // ...
    }

Are there any problems doing this? The templates are using `strong` as are the automatically generated properties created when connecting directly to the header from the &#39;Interface Builder&#39; editor, but why? The `UIViewController` already has a `strong` reference to its `view` which retains its subviews.

Should IBOutlets be strong or weak under ARC?

Every time my app crashes Xcode highlights the UIApicationMain() call in the main() function as the line that caused the crash. In some cases that used to be normal (segmentation fault for example) but the crash I am trying to deal with is a simple SIGABRT with detailed information logged in the console:

    *** Terminating app due to uncaught exception &#39;NSInvalidArgumentException&#39;, reason: &#39;-[__NSCFDictionary setObject:forKey:]: attempt to insert nil value (key: Date)&#39;

Xcode used to show the line just right with older SDKs but since i upgraded to Xocde 4.2 that changed. 
It is pretty obvious that Xcode knows exactly what caused the crash (or could know), but its still not showing the actual line. Is there any fix or workaround for this?

Xcode doesn&#39;t show the line that causes a crash

Is there any way to have a Transition/animation effect while replacing an existing viewcontroller as rootviewcontroller with a new one in the appDelegate?

RootViewController Switch Transition Animation

Is it possible create an `UIImage` or an `UIImageView` with rounded corners? Because I want take an `UIImage` and show it inside an `UIImageView`, but I don&#39;t know how to do it.

IOS: create a UIImage or UIImageView with rounded corners

Is there a way to know if a `UIScrollView` has reached the top or bottom? Possibly in the method:

    - (void)scrollViewDidEndDragging:(UIScrollView *)scrollView 
                      willDecelerate:(BOOL)decelerate

Check if a UIScrollView reached the top or bottom

I am trying to check to see if a string that I am going to use as URL starts with http. The way I am trying to check right now doesn&#39;t seem to be working. Here is my code:

    NSMutableString *temp = [[NSMutableString alloc] initWithString:@&quot;http://&quot;];
    if ([businessWebsite rangeOfString:@&quot;http&quot;].location == NSNotFound){
        NSString *temp2 = [[NSString alloc] init];
        temp2 = businessWebsite;
        [temp appendString:temp2];
        businessWebsite = temp2;
        NSLog(@&quot;Updated BusinessWebsite is: %@&quot;, businessWebsite);
    }
    
    [web setBusinessWebsiteUrl:businessWebsite];
Any ideas? 

How to see if an NSString starts with a certain other string?

I have an app where the user can choose an image either from the built-in app images or from the iphone photo library. I use an object Occasion that has an `NSString` property to save the `imagePath`. 

Now in the case of the built-in app images I do get the file name as an `NSString` an save in the `[occasion imagePath]`. But in the 2nd case where the user picks an image form the photo library I get an `NSURL` which I want to convert to an `NSString` to be able to save it in `[occasion imagePath`].

Is it possible to convert the `NSURL` to an `NSString`?


Convert an NSURL to an NSString

I have a `NSString` like this:

    http://www.

but I want to transform it to:

    http%3A%2F%2Fwww.

How can I do this?

Objective-C and Swift URL encoding

I have a URL string (`NSString`) with spaces and `&amp;` characters.  How do I url encode the entire string (including the `&amp;` ampersand character and spaces)?

How do I URL encode a string

In my iOS 5 app, I have an `NSString` that contains a JSON string. I would like to deserialize that JSON string representation into a native `NSDictionary` object.

     &quot;{\&quot;password\&quot; : \&quot;1234\&quot;,  \&quot;user\&quot; : \&quot;andreas\&quot;}&quot;
 
### I tried the following approach:

    NSDictionary *json = [NSJSONSerialization JSONObjectWithData:@&quot;{\&quot;2\&quot;:\&quot;3\&quot;}&quot;
                                    options:NSJSONReadingMutableContainers
                                      error:&amp;e];  

### But it throws the a runtime error. What am I doing wrong?

    -[__NSCFConstantString bytes]: unrecognized selector sent to instance 0x1372c 
    *** Terminating app due to uncaught exception &#39;NSInvalidArgumentException&#39;,
    reason: &#39;-[__NSCFConstantString bytes]: unrecognized selector sent to instance 0x1372c&#39;

Content Type	Original Author	Original Content on Stackoverflow
Question	Suchi	View Question on Stackoverflow
Solution 1 - Objective C	user747858	View Answer on Stackoverflow
Solution 2 - Objective C	ughoavgfhw	View Answer on Stackoverflow

Objective C - How to concatenate an entire array of strings?

Objective C Problem Overview

Objective C Solutions

Solution 1 - Objective C

Solution 2 - Objective C

How do I properly escape data for a Makefile?

Math operations with null

Attributions