Xcode 4.0 Error: Apple Match-O Linker(Id) Error “…”, referenced from:

Upgrading to Xcode 4.0 from Xcode 3.0 requires some work. This is a very common error. The fix is simple but it takes a while to identify the source.

Errors:

Apple Match-O Linker(Id) Error “…”, referenced from:

ld: warning: directory ‘/Users/UserName/Development/Project/frameworks’ following -F not found

Fix:

• Enter FRAMOWORK_SEARCH_PATHS into the search box
• Remove that directory from the “framework search paths” in the build settings for the project, or for that target

Another Error:

ld: warning: directory not found for option ‘-L/Users/UserName/Desktop/student/../../../../Downloads/ProjectName/ClassName/lib/Debug-iphoneos’

-L is for specifying additional library search path directories. The directory it mentions in the error doesn’t exist.

In the given folder look into the project settings. Update the current directory for the current version of the SDK. Use above fix.

Xcode 4.0 Error: No architectures to compile for – Facebook iOS SDK

Upgrading Xcode projects from Xcode 3.x to Xcode 4.0 are not that simple. It does involve a lot of “detective” work like solving murder mystery.

In this case it happens on Facebook iOS SDK sample project. The codes work perfectly fine in Xcode 3 yet the same code won’t run in Xcode 4.0 Simulator. After trying many suggestions from Apple Developer Forum, I found the only working solution.

[EROR] No architectures to compile for (ARCHS=i386, VALID_ARCHS=armv6).

“No architectures to compile for” means “Valid Architectures” field is empty. Update it to $(ARCHS_STANDARD_32_BIT) and you’ll see the usual armv6 armv7. This happens in XCode 4 after updating “Base SDK” to “Latest SDK”.

Instruction:

• Select Project in the Navigator left panel in Xcode 4
• Select Targets
• In Build Settings, enter VALID_ARCHS in the search box to show Valid Architectures
• Enter $(ARCHS_STANDARD_32_BIT) in the value column
• It should show armv6 armv7
• Run

Don’t use setAlternateColor: on UISwitch

According to Apple documentation, it is recommended not to change UISwitch.

By default UISwitch shows a blue button with “ON” label and white button with “OFF” label. API won’t allow you to change the font name, font size, font style, font color, button color on UISwitch.

Even though there are many examples on how to use setAlternateColor: method to change the default UISwitch button from blue color to orange color, this is not recommended. Your app will be rejected if you use it.

The UISwitch class is not customizable.

You would have to build your own custom switch. It is in general difficult to subclass UIControl and reimplement UISwitch. There are other work around approaches to recreate Switch using png images.

Disable & Enable Idle Timer in iOS SDK

By default, the idle timer will dim the screen after a period of non use and then turn the power to the screen off. You may need to disable idle timer on a specific app such as a Flash light app or location-based app.

– (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
…
}

Add the following line:
[application setIdleTimerDisabled:YES];

– (void)applicationWillTerminate:(UIApplication *)application {
…
}

Add the following line to re-enable the idle timer:
[application setIdleTimerDisabled:NO];

This won’t work on the Simulator but it definitely works on device.

Debugging using printf() in Xcode Console

You can use printf() function inside .m file to indicate the app status such as application starts and ends.

In Xcode, select AppDelegate.m file, insert a line inside applicationDidFinishLaunching: method:

– (void)applicationDidFinishLaunching:(UIApplication *)application {
…
}

Add the following:
printf(“%s\n”, __FUNCTION__);

Note: The __Function__ has two underscores before and after the FUNCTION.

Add the same line to applicationWillTerminate: method

– (void)applicationWillTerminate:(UIApplication *)application {
…
}

You should be able to see the printed output inside Xcode Console when you launch the app

[AppDelegate applicationDidFinishLaunching:]

After you exit the app by pressing the Home button on the iPhone simulator, you will see this printed output
[AppDelegate applicationWillTerminate:]

UIDevice Properties

Currently these are the most popular common UIDevice properties. It shows the device name, device identifier, device model, device system name, and device system version.

You can print these properties inside the Console for debugging.

NSLog(@”Device Name: %@”, [UIDevice currentDevice].name);
NSLog(@”UDID: %@”, [UIDevice currentDevice].uniqueIdentifier);
NSLog(@”Device Model: %@”, [UIDevice currentDevice].model);
NSLog(@”System Name: %@”, [UIDevice currentDevice].systemName);
NSLog(@”System Version: %@”, [UIDevice currentDevice].systemVersion);
NSLog(@”User Interface: %@”, [UIDevice currentDevice].userInterfaceIdiom);

If you would like to print it in a label, then you can assign an NSInteger object to the UIDevice property. Assign the UILabel text to the NSString object.

// Show Device Name
NSString *nameString = [UIDevice currentDevice].name;
nameLabel.text = nameString;

You can also print Core Foundation object in Console.

CFShow([[UIDevice currentDevice] model]);
printf(“–\n”);

Constant in Objective-C

This is a very tricky task to handle constants in Objective-C. The most suggested approach is to define global, public or private constants. This will work only if you don’t expect to put the same constant inside a loop.

In the header file

// Constants.h
extern NSString * const strConstant;

You can include this file in each file that uses the constants or in the pre-compiled header for the project.

// Constants.m
NSString * const strConstant = @"Constant";

Constants.m should be added to your application/framework’s target to link it to product.

It is suggested that the advantage of using string constants instead of #define‘d constants is that you can test for equality using pointer comparison (stringInstance == strConstant) which is much faster than string comparison ([stringInstance isEqualToString:strConstant]).

// Constants.h
#define MY_CONSTANT @"my_constant"

Or even better
// Constants.h
extern NSString * const MY_CONSTANT;
// Constants.m
NSString * const MY_CONSTANT = @"my_constant";

If you need a non global constant, you should use static keyword. Static constant is not visible outside the file.

// Constants.m
static NSString * const CONSTANT = @"my_constant";

Another quick dirty way of declaring global constants is to put constant declaration into pch file instead of .h or .m files.

To declare integer instead of string in Objective-C, you will use NSInteger. This is Apple preferred way of declaring Objective-C integer.

NSInteger const counter = 0;

However if you are going to use this method to declare NSInteger and use it inside a loop, then you are in trouble.

Warning:

Assignment of read-only variable ‘counter’

If you need to use a constant inside a IF statement and iterate the constant inside a class instance or method, you would have to use static keyword.

You can add static int outside @implement.

static int counter = 0;

– (void)showTimer {
counter += 1;
}

UITableView Hello World

Usually writing a tutorial blog takes a lot of time and effort to document every step and explain all details. I have seen many HelloWorld app that show very little on how iPhone app and SDK work. I include the best HelloWorld tutorial and example I found.

These are the most important building blocks of iPhone App. However usually developers don’t start with new app and may be working on existing app. Sometimes developers never get to build new View Controller and/or view. You won’t remember all the details in each step. It’s nice to reference this kind of Hello World example.

It’s nice to see how a navigation-based app with minimal functionality and show how the navigation bar and button work.

UITableView Hello World

http://icodeblog.com/2008/07/26/iphone-programming-tutorial-hello-world/

Add View Controller and View and Back Button to HelloWorld

http://icodeblog.com/2008/08/03/iphone-programming-tutorial-transitioning-between-views/

Note: Remember setText is deprecated in OS 3.2 and warning will appear in this Hello World example.

Populating UITableView with NSArray

http://icodeblog.com/2008/08/08/iphone-programming-tutorial-populating-uitableview-with-an-nsarray/

I am including code snippet to show how to gain access to UIApplication delegate to return the NSArray object in UITable row.

In RootViewController.m

// Customize the number of rows in the table view.
– (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {

// Gain access to Application delegate
HelloNavigationAppDelegate *appDelegate = (HelloNavigationAppDelegate *)[[UIApplication sharedApplication] delegate];
// Return no of rows based on no. of objects in array
return appDelegate.fruits.count;

}

// Customize the appearance of table view cells.
– (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

static NSString *CellIdentifier = @”Cell”;

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:CellIdentifier] autorelease];
}

// Gain access to Application delegate
HelloNavigationAppDelegate *appDelegate = (HelloNavigationAppDelegate *)[[UIApplication sharedApplication] delegate];
Fruit *f = (Fruit *)[appDelegate.fruits objectAtIndex:indexPath.row];
cell.textLabel.text = f.name;

// Configure the cell.
return cell;
}

I have rewritten the UITableView Hello World sample in iPhone SDK 3.2 and replaced the deprecated API that no longer support UITableView. You can download the latest version here

UITableView deprecated setText in iPhone SDK 3.0

By default Navigation-based app use UITableView.

In RootViewController.m, you would declare the no. of row in tableView: method. Here you increase the row from 0 to 1 to display one row.

// Customize the number of rows in the table view.
– (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
return 1; // Modify from 0 to 1
}

cell.text and setText: are deprecated in iPhone SDK 3.2. It would give you warning but error in red.

So don’t use:

[cell setText:@”Next View”];

cell.text = @”Next View”;

Use cell.textLabel.text = @”Next View”;

// Customize the appearance of table view cells.
– (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

static NSString *CellIdentifier = @”Cell”;

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
}

// Added
cell.textLabel.text = @”Next View”;

// Configure the cell.
return cell;
}

Supporting All Orientations in iPad App

One of the most popular disapproval or rejection reasons for iPad app is your app doesn’t support all orientations.

iPad requires 4 additional Default images:

• Default-LandscapeRight.png
• Default-PortraitUpsideDown.png
• Default-LandscapeLeft.png
• Default-Portrait.png

iPad’s screen size is 1024 x 768 pixels. 20 pixel is the status bar.

• Default-Portrait.png * 768w x 1004h
• Default-PortraitUpsideDown.png 768w x 1004h
• Default-Landscape.png ** 1024w x 748h
• Default-LandscapeLeft.png 1024w x 748h
• Default-LandscapeRight.png 1024w x 748h
• Default.png Not recommended

* If you have not specified a Default-PortraitUpsideDown.png file, this file will take precedence.

** If you have not specified a Default-LandscapeLet.png or Default-LandscapeRight.png image file, this file will take precedence.

Again it recommends you to put these Default images at the Project root. If you don’t give precise image dimensions, your iPad app will get confused and will not display those default images.

However it would not do the trick even you place all the default images at the project root. As it is, iPad would display one Default image regardless of iPad orientation. Adding conditional codes in Objective-C won’t show any effect.

// This won’t do much
– (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {
// Return YES for supported orientations
return YES;
}

Apple documentation didn’t list it on their documentation even it is a must requirement for approving iPad app.

Apparently you would have to add a new field “UISupportedInterfaceOrientations” to info.plist.

UISupportedInterfaceOrientations must be defined as Array in Type. Add the following items into the array

• UIInterfaceOrientationPortrait
• UIInterfaceOrientationPortraitUpsideDown
• UIInterfaceOrientationLandscapeLeft
• UIInterfaceOrientationLandscapeRight

Apple SDK templates should have included these expected settings on iPhone OS 3.2 but it didn’t. Apple expects developers to repeat these steps in building every new iPad app.