Development and programming answers

IOS: Difference between atomic and non-atomic attributes

What do atomic and nonatomic mean in property declarations?

@property(nonatomic, retain) UITextField *userName;
@property(atomic, retain) UITextField *userName;
@property(retain) UITextField *userName;

Let's talk about the operational difference:

What do atomic and nonatomic mean in property declarations? atomic was added as a keyword in recent versions of llvm/clang).

Assuming that you are @synthesizing the method implementations, atomic vs. non-atomic changes the generated code. If you are writing your own setter/getters, atomic/nonatomic/retain/assign/copy are merely advisory. (Note: @synthesize is now the default behavior in recent versions of LLVM. There is also no need to declare instance variables; they will be synthesized automatically, too, and will have an _ prepended to their name to prevent accidental direct access).

With "atomic", the synthesized setter/getter will ensure that a whole value is always returned from the getter or set by the setter, regardless of setter activity on any other thread. That is, if thread A is in the middle of the getter while thread B calls the setter, an actual viable value -- an autoreleased object, most likely -- will be returned to the caller in A.

In nonatomic, no such guarantees are made. Thus, nonatomic is considerably faster than "atomic".

What "atomic" does not do is make any guarantees about thread safety. If thread A is calling the getter simultaneously with thread B and C calling the setter with different values, thread A may get any one of the three values returned -- the one prior to any setters being called or either of the values passed into the setters in B and C. Likewise, the object may end up with the value from B or C, no way to tell.

Ensuring data integrity -- one of the primary challenges of multi-threaded programming -- is achieved by other means.

iOS How to send SMS with iPhone

10:08 AM 1

Restrictions

If you could send an SMS within a program on the iPhone, you'll be able to write games that spam people in the background. I'm sure you really want to have spams from your friends, "Try out this new game! It roxxers my boxxers, and yours will be too! roxxersboxxers.com!!!! If you sign up now you'll get 3,200 RB points!!"

Apple has restrictions for automated (or even partially automated) SMS and dialing operations. (Imagine if the game instead dialed 911 at a particular time of day)

Your best bet is to setup an intermediate server on the internet that uses an online SMS sending service, and send the SMSs via that route if you need complete automation. (ie, your program on the iPhone sends a UDP packet to your server, which sends the real SMS)

iOS 4 Update

iOS 4, however, now provides a viewcontroller you can import into your application. You prepopulate the SMS fields, then the user can initiate the SMS send within the controller. Unlike using the "sms:..." url format, this allows your application to stay open, and allows you to populate both the to and the body fields. You can even specify multiple recipients.

This prevents applications from sending automated SMS without the user explicitly aware of it. You still cannot send fully automated SMS from the iPhone itself, it requires some user interaction. But this at least allows you to populate everything, and avoids closing the application.

The MFMessageComposeViewController class is well documented, and tutorials show how easy it is to implement.

iOS 5 Update

iOS 5 includes messaging for iPod touch and iPad devices, so while I've not yet tested this myself, it may be that all iOS devices will be able to send SMS via MFMessageComposeViewController. If this is the case, then Apple is running an SMS server that sends messages on behalf of devices that don't have a cellular modem.

iOS 6 Update

No changes to this class.

iOS 7 Update

You can now check to see if the message medium you are using will accept a subject or attachments, and what kind of attachments it will accept. You can edit the subject and add attachments to the message, where the medium allows it.

Limitations to this class

Keep in mind that this won't work on phones without iOS 4, and it won't work on the iPod touch or the iPad, except, perhaps, under iOS 5. You must either detect the device and iOS limitations prior to using this controller, or risk restricting your app to recently upgraded 3G, 3GS, and 4 iPhones.

However, an intermediate server that sends SMS will allow any and all of these iOS devices to send SMS as long as they have internet access, so it may still be a better solution for many applications. Alternately, use both, and only fall back to an online SMS service when the device doesn't support it.

How to embed custom font in iOS iphone app

10:01 AM 0

iOS 3.2 and later support this. Straight from the What's New in iPhone OS 3.2 doc:

Custom iOs Font Support
Applications that want to use custom fonts can now include those fonts in their application bundle and register those fonts with the system by including the UIAppFonts key in their Info.plist file. The value of this key is an array of strings identifying the font files in the application’s bundle. When the system sees the key, it loads the specified fonts and makes them available to the application.

Once the fonts have been set in the Info.plist, you can use your custom fonts as any other font in IB or programatically.

There is an ongoing thread on Apple Developer Forums:
https://devforums.apple.com/thread/37824 (login required) and here's an excellent and simple 3 steps tutorial on how to achieve this (broken link removed)

Add your custom font files into your project using Xcode as a resource
Add a key to your Info.plist file called UIAppFonts.
Make this key an array
For each font you have, enter the full name of your font file (including the extension) as items to the UIAppFonts array
Save Info.plist
Now in your application you can simply call [UIFont fontWithName:@"CustomFontName" size:12]to get the custom font to use with your UILabels and UITextViews, etc…

Also: Make sure the fonts are in your Copy Bundle Resources.

Making filetypes handling association with ios iphone app

9:41 AM 0

File type handling is new with iPhone OS 3.2, and is different than the already-existing custom URL schemes. You can register your application to handle particular document types, and any application that uses a document controller can hand off processing of these documents to your own application.

For example, Molecules handles the .pdb and .pdb.gz file types, if received via email or in another supported application.

To register support, you will need to have something like the following in your Info.plist:

<key>CFBundleDocumentTypes</key>
<array>
    <dict>
        <key>CFBundleTypeIconFiles</key>
        <array>
            <string>Document-molecules-320.png</string>
            <string>Document-molecules-64.png</string>
        </array>
        <key>CFBundleTypeName</key>
        <string>Molecules Structure File</string>
        <key>CFBundleTypeRole</key>
        <string>Viewer</string>
        <key>LSHandlerRank</key>
        <string>Owner</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>com.sunsetlakesoftware.molecules.pdb</string>
            <string>org.gnu.gnu-zip-archive</string>
        </array>
    </dict>
</array>

Two images are provided that will be used as icons for the supported types in Mail and other applications capable of showing documents. The LSItemContentTypes key lets you provide an array of Uniform Type Identifiers (UTIs) that your application can open. For a list of system-defined UTIs, see Apple's Uniform Type Identifiers Reference. Even more detail on UTIs can be found in Apple'sUniform Type Identifiers Overview. Those guides reside in the Mac developer center, because this capability has been ported across from the Mac.

One of the UTIs used in the above example was system-defined, but the other was an application-specific UTI. The application-specific UTI will need to be exported so that other applications on the system can be made aware of it. To do this, you would add a section to your Info.plist like the following:

<key>UTExportedTypeDeclarations</key>
<array>
    <dict>
        <key>UTTypeConformsTo</key>
        <array>
            <string>public.plain-text</string>
            <string>public.text</string>
        </array>
        <key>UTTypeDescription</key>
        <string>Molecules Structure File</string>
        <key>UTTypeIdentifier</key>
        <string>com.sunsetlakesoftware.molecules.pdb</string>
        <key>UTTypeTagSpecification</key>
        <dict>
            <key>public.filename-extension</key>
            <string>pdb</string>
            <key>public.mime-type</key>
            <string>chemical/x-pdb</string>
        </dict>
    </dict>
</array>

This particular example exports the com.sunsetlakesoftware.molecules.pdb UTI with the .pdb file extension, corresponding to the MIME type chemical/x-pdb.

With this in place, your application will be able to handle documents attached to emails or from other applications on the system. In Mail, you can tap-and-hold to bring up a list of applications that can open a particular attachment.

When the attachment is opened, your application will be started and you will need to handle the processing of this file in your -application:didFinishLaunchingWithOptions: application delegate method. It appears that files loaded in this manner from Mail are copied into your application's Documents directory under a subdirectory corresponding to what email box they arrived in. You can get the URL for this file within the application delegate method using code like the following:

NSURL *url = (NSURL *)[launchOptions valueForKey:UIApplicationLaunchOptionsURLKey];

Note that this is the same approach we used for handling custom URL schemes. You can separate the file URLs from others by using code like the following:

if ([url isFileURL])
{
    // Handle file being passed in
}
else
{
    // Handle custom URL scheme
}

How to migrate applications for iphone 5 resolution

5:08 PM 0

The new iPhone 5 display has a new aspect ratio and a new resolution (640 x 1136 pixels).

To make applications "universal" for both the older displays and the new widescreen aspect ratio follow the following steps:

Download and install latest version of Xcode.
Set a 4-inch launch image for your app. This is how you get 1136 px screen height (without it, you will get 960 px with black margins on top and bottom).
Test your app, and hopefully do nothing else, since everything should work magically if you had set auto resizing masks properly.
If you didn't, adjust your view layouts with proper auto resizing masks or look into Auto Layout if you only want to support iOS 6 going forward.
If there is something you have to do for the larger screen specifically, then it looks like you have to check height of [[UIScreen mainScreen] bounds] (or applicationFrame, but then you need to consider status bar height if it's present) as there seems to be no specific API for that.

Example:

CGRect screenBounds = [[UIScreen mainScreen] bounds];
if (screenBounds.size.height == 568) {
    // code for 4-inch screen
} else {
    // code for 3.5-inch screen
}

Also note: The auto-rotation API has changed completely, take a look at that as well if your application supports any rotation other than default.

Applying CSS to an iframe

12:22 PM 0

There are two different things here: the style of the iframe block and the style of the page embedded in the iframe. You can set the style of the iframe block the usual way:

<iframe name='iframe1' id="iframe1" src="empty.htm" frameborder="0" border="0" cellspacing="0" style="border-style: none;width: 100%; height: 120px;"></iframe>

The style of the page embedded in the iframe must be either set by including it in the child page:

<link type="text/css" rel="Stylesheet" href="Style/simple.css" />

Or it can be loaded from the parent page with Javascript:

var cssLink = document.createElement("link") 
cssLink.href = "style.css"; 
cssLink .rel = "stylesheet"; 
cssLink .type = "text/css"; 
frames['frame1'].document.body.appendChild(cssLink);

HTML: Removing spaces between inline-block elements

1:36 PM 0

Given this HTML:

<p>
    <span> Foo </span>
    <span> Bar </span>
</p>

and this CSS:

span { 
    display:inline-block;
    width:100px;
}

as a result, there will be a 4px wide space between the SPAN elements. Demo: http://jsfiddle.net/dGHFV/

I understand why this happens, and I also know that I could get rid of that space by removing the white-space between the SPAN elements in the HTML source code, like so:

<p>
    <span> Foo </span><span> Bar </span>
</p>

However, I was hoping for a CSS solution that doesn't require the HTML source code to be tampered with.

I know how to solve this with JavaScript - by removing the Text nodes from the container element (the paragraph), like so:

// jQuery
$('p').contents().filter(function() { return this.nodeType === 3; }).remove();

Answer:

Since this answer has become rather popular, I'm rewriting it significantly.

Let's not forget the actual question that was asked:

How to remove the space between inline-block elements? I was hoping for a CSS solution that doesn't require the HTML source code to be tampered with. Can this issue be solved with CSS alone?

It is possible to solve this problem with CSS alone, but there are no completely robust CSS fixes.

The solution I had in my initial answer was to add font-size: 0 to the parent element, and then declare a sensible font-size on the children.

http://jsfiddle.net/thirtydot/dGHFV/1361/

This works in recent versions of all modern browsers. It works in IE8. It does not work in Safari 5, but it does work in Safari 6. Safari 5 is nearly a dead browser (1.49%, July 2013).

Most of the possible issues with relative font sizes are not complicated to fix.

However, while this is a reasonable solution if you specifically need a CSS only fix, it's not what I recommend if you're free to change your HTML (as most of us are).

This is what I, as a reasonably experienced web developer, actually do to solve this problem:

<p>
    <span>Foo</span><span>Bar</span>
</p>

Yes, that's right. I remove the whitespace in the HTML between the inline-block elements.

It's easy. It's simple. It works everywhere. It's the pragmatic solution.

You do sometimes have to carefully consider where whitespace will come from. Will appending another element with jQuery add whitespace? No, not if you do it properly.

Let's go on a magical journey of different ways to remove the whitespace, with some new HTML:

<ul>
    <li>Item 1</li>
    <li>Item 2</li>
    <li>Item 3</li>
</ul>

You can do this, as I usually do:

<ul>
    <li>Item 1</li><li>Item 2</li><li>Item 3</li>

</ul>

http://jsfiddle.net/thirtydot/dGHFV/1362/

Or, this:

<ul>
    <li>Item 1</li
    ><li>Item 2</li
    ><li>Item 3</li>
</ul>

Or, use comments:

<ul>
    <li>Item 1</li><!--
    --><li>Item 2</li><!--
    --><li>Item 3</li>
</ul>

Or, you can even skip certain closing tags entirely (all browsers are fine with this):

<ul>
    <li>Item 1
    <li>Item 2
    <li>Item 3
</ul>

Now that I've gone and bored you to death with "one thousand different ways to remove whitespace, by thirtydot", hopefully you've forgotten all about font-size: 0.

CSS: How to align horizontally one div inside another div

1:28 PM 0

How do I horizontally center a div in a div with CSS (if it's possible at all)? The outer div has 100%:

<div id="outer" style="width:100%">  
    <div id="inner">Foo foo</div>
</div>

In this example the outter div have 100% width, to align horizontally the inner div we can apply this code in the inner div:

#inner {
    width: 50%;
    margin: 0 auto;
}

Of course, you don't have to set the width to 50%. Any width less than the containing div will work. The margin: 0 auto is what does the actual centering.

If you are targeting IE8+, it might be better to have this instead:

#inner {
    display: table;
    margin: 0 auto;
}

It will make the inner element center horizontally and it works without setting a specific width.

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