iOs to web connections - JSON

You will love this framework.
And you will love this tool.
For learning about JSON you might like this resource.
And you'll probably love this tutorial.

Mobile App development SDKs

This a list of mobile SDKs, their links and info about each;
Phonegap - another HTML5 SDK

Sencha - another HTML5 SDK

Here's a great article about various platforms, including the table summary below;

Before going into the details of each SDK, in the table below we can analyze the programming languages and platforms supported by each tool.

SDK	Language	Win Support	iOS Support	Android Support	Symbian Support	Console Support
Shiva3d	C++	Yes	Yes	Yes	No	Wii
SIO2	C-C++	Yes	Yes	Yes	No	No
Unity	JavaScript, C#, Python	Yes	Yes	Yes	No	Xbox, PS3, Wii
Corona	Lua	Yes	Yes	Yes	No	No
PhoneGap	HTML, Javascript	Yes	Yes	Yes	Yes	No
Titanium Mobile	HTML, Javascript	No	Yes	Yes	No	No
cocos2d-x	C++	Yes	Yes	Yes	No	No
Edgelib	C++	Yes	Yes	Yes	Yes	No
Moai	C++	Yes	Yes	Yes	No	No
Marmalade	C-C++	Yes	Yes	Yes	Yes	No
Simple DirectMedia Layer	C++	Yes	Yes	No	Yes	No

iPhone screen rotation logic

This is the proper implementation for screen rotation (example is portrait or upside down portrait);

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
            if ((interfaceOrientation == UIInterfaceOrientationPortrait) || (interfaceOrientation
            ==UIInterfaceOrientationPortraitUpsideDown)) {   
                 return YES;
             } else {
                 return NO;
    }
}

the other possible states are UIInterfaceOrientationLandscapeLeft or UIInterfaceOrientationLandscapeRight.

You should also set the view mode in the view's Attribute inspector on the storyboard.

Xcode compile error

-symbol(s) not found for architecture i386

Have had this error a number of times at compile time.  There are no apparent errors or warning prior to compile, but it fails nonetheless.
You need to read the bottom portion carefully for clues.  This time it said CoreDataTableViewController was not found.  I deleted these files and re-imported them, and it worked!
Go figure, apparently the original import routine (drag files to file organizer) didn't work.

duplicate symbol _OBJC_IVAR_$ - Xcode linking error

I received this error today after inputing Apple's "Your third iOS Program", SimpleTextEditor.xcodeproj.
After struggling thru the error message, and replacing a lot of the code with cut/pastes from Apple, I went to their forum, and found the problem.

I mistyped this statement - #import "STESimpleTextDocument.m" as an import for the DetailViewController header file. It should be .h

 Forums rock!