Navigation Bar Background Color and Buttons Tint Color

To change the background color of navigation bar and the tint color of bar button items, no code is needed.

In the storyboard, click on the navigation bar of your navigation controller.

Set the Bar Tint for changing the background color. And Tint inside the View section.

Below shows how to set the background to blue and buttons to white.

Navigation Bar Background Color and Buttons Tint Color

Hide Status Bar

Starting from iOS 7, there are 2 ways to hide the status bar. One is to hide the status bar in all view controllers, while the other is controller specific.

  1. App-based setting

Set “View controller-based status bar appearance” in target’s info to NO.

then in the app delegate, inside application:didFinishLaunchingWithOptions:, add

[application setStatusBarStyle:UIStatusBarStyleLightContent];
  1. Controller-based setting

Set “View controller-based status bar appearance” to YES.

Inside viewDidLoad, add

[self setNeedsStatusBarAppearanceUpdate]

and then add the following function:

-(UIStatusBarStyle)preferredStatusBarStyle{ 
    return UIStatusBarStyleLightContent; 
}
Hide Status Bar

NSUserDefaults KVO in iOS7

Though its not well documented, NSUserDefaults do support key-value observing in iOS7. The following code works:

- (void)viewDidLoad{
  [super viewDidLoad];
  NSUserDefaults *ud = [NSUserDefaults standardUserDefaults];
  [ud addObserver:self forKeyPath:@"bar" options:NSKeyValueObservingOptionOld|NSKeyValueObservingOptionNew context:nil];
  [ud setObject:@"foo" forKey:@"bar"];
}

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
  NSLog(@"%@", change);
}

Its much more convenient then using NSUserDefaultsDidChangeNotification, since we do know exactly which key is changing.

As the hardware of mobile devices become more and more powerful, I hope the support of key binding could be actualised in near future 🙂

NSUserDefaults KVO in iOS7

Objective C Property Attributes

Just read a post about Objective C property attributes. I wanna make some extra notes on this topic:

1. “weak” vs “assign”

We generally use weak for Objective-C objects that we don’t need to retain, e.g.

@property (weak) IBOutlet UIButton aButton;

because its always good to nil an object if it has been deallocated.

On the other hand, we could use assign for C primitives, e.g.

@property BOOL isGood;

because C primitives has nothing to do with retain count and deallocation, simply assign the value is good enough.

Note that assign is the default property attribute, we can skip it for C primitives for cleaner code.

2. The default attribute of property vs variable

There are 2 kinds of default: property and variable

For property, the default attribute is “assign”

For variable (ivar or local variable), the default ownership qualifier is “__strong”

Don’t mix up “strong” in property and “__strong” in variable. They are different things (see below).

Also remember the default property attribute is “assign”, not “strong”

3. Implicit attribute for the default

The explicit version of

@property BOOL isGood;

should be:

@property (atomic, assign, readwrite) BOOL isGood

so skipping the attributes by using the default is fine for C primitives in most cases.

However, we better explicitly state the attributes for Objective-C objects. Because we seldom want “assign” for objects.

For ivar and local variable,

NSString *str;

is equivalent to

__strong NSString *str;

so if you set it as an ivar, the compiler will automatically retain it for you when you assign a value for it. Which behave differently from not using ARC.

4. Relationship between property attributes and ownership qualifiers

Here listed their relationships according to the official documentation

  • assign implies __unsafe_unretained ownership.
  • copy implies __strong ownership, as well as the usual behavior of copy semantics on the setter.
  • retain implies __strong ownership.
  • strong implies __strong ownership.
  • unsafe_unretained implies __unsafe_unretained ownership.
  • weak implies __weak ownership.

So for property attributes in ARC, practically we can assume assign = unsafe_unretained, and strong = retain.

Objective C Property Attributes

GData Static Library for Specific API

From my previous posts I mentioned how to deploy GData by using all-in-one static library, and official build procedures. But both methods have their trade-offs:

  • Using all-in-one static library is easy but need to import a big image file.
  • Following official procedures generate small image file but tedious. Also, you need to re-compile hundreds of source file every time  after cleaning your build, which is quite clumsy if you are under active development.

So the question is: How can we generate GData static library for specific API, such that its reasonably small and save some re-compiling time after cleaning the build? Here is how:

  • Download GData Objective-C client and open its project in XCode
  • Select the Build Settings of GDataTouchStaticLib target
  • Add -DGDATA_REQUIRE_SERVICE_INCLUDES=1 in the Debug setting of “Other C Flags”

  • Suppose I want to implement Youtube API only, add -DGDATA_INCLUDE_YOUTUBE_SERVICE=1 in both Debug and Release setting of “Other C Flags”. Just change this entry to other API name (say -DGDATA_INCLUDE_CONTACTS_SERVICE=1) if you want to implement other API. You can see all the API names in GData Srouces folder in the source tree.
  • In Build Phases of the same target, click Add Build Phase at the lower right corner and select Add Run Script. Then paste the following shell script:
# Version 2.0 (updated for Xcode 4, with some fixes)
# Changes:
#    - Works with xcode 4, even when running xcode 3 projects (Workarounds for apple bugs)
#    - Faster / better: only runs lipo once, instead of once per recursion
#    - Added some debugging statemetns that can be switched on/off by changing the DEBUG_THIS_SCRIPT variable to "true"
#    - Fixed some typos
#
# Purpose:
#   Create a static library for iPhone from within XCode
#   Because Apple staff DELIBERATELY broke Xcode to make this impossible from the GUI (Xcode 3.2.3 specifically states this in the Release notes!)
#   ...no, I don't understand why they did this!
#
# Author: Adam Martin - http://twitter.com/redglassesapps
# Based on: original script from Eonil (main changes: Eonil's script WILL NOT WORK in Xcode GUI - it WILL CRASH YOUR COMPUTER)
#
# More info: see this Stack Overflow question: http://stackoverflow.com/questions/3520977/build-fat-static-library-device-simulator-using-xcode-and-sdk-4

#################[ Tests: helps workaround any future bugs in Xcode ]########
#
DEBUG_THIS_SCRIPT="false"

if [ $DEBUG_THIS_SCRIPT = "true" ]
then
echo "########### TESTS #############"
echo "Use the following variables when debugging this script; note that they may change on recursions"
echo "BUILD_DIR = $BUILD_DIR"
echo "BUILD_ROOT = $BUILD_ROOT"
echo "CONFIGURATION_BUILD_DIR = $CONFIGURATION_BUILD_DIR"
echo "BUILT_PRODUCTS_DIR = $BUILT_PRODUCTS_DIR"
echo "CONFIGURATION_TEMP_DIR = $CONFIGURATION_TEMP_DIR"
echo "TARGET_BUILD_DIR = $TARGET_BUILD_DIR"
fi

#####################[ part 1 ]##################
# First, work out the BASESDK version number (NB: Apple ought to report this, but they hide it)
#    (incidental: searching for substrings in sh is a nightmare! Sob)

SDK_VERSION=$(echo ${SDK_NAME} | grep -o '.\{3\}$')

# Next, work out if we're in SIM or DEVICE

if [ ${PLATFORM_NAME} = "iphonesimulator" ]
then
OTHER_SDK_TO_BUILD=iphoneos${SDK_VERSION}
else
OTHER_SDK_TO_BUILD=iphonesimulator${SDK_VERSION}
fi

echo "XCode has selected SDK: ${PLATFORM_NAME} with version: ${SDK_VERSION} (although back-targetting: ${IPHONEOS_DEPLOYMENT_TARGET})"
echo "...therefore, OTHER_SDK_TO_BUILD = ${OTHER_SDK_TO_BUILD}"
#
#####################[ end of part 1 ]##################

#####################[ part 2 ]##################
#
# IF this is the original invocation, invoke WHATEVER other builds are required
#
# Xcode is already building ONE target...
#
# ...but this is a LIBRARY, so Apple is wrong to set it to build just one.
# ...we need to build ALL targets
# ...we MUST NOT re-build the target that is ALREADY being built: Xcode WILL CRASH YOUR COMPUTER if you try this (infinite recursion!)
#
#
# So: build ONLY the missing platforms/configurations.

if [ "true" == ${ALREADYINVOKED:-false} ]
then
echo "RECURSION: I am NOT the root invocation, so I'm NOT going to recurse"
else
# CRITICAL:
# Prevent infinite recursion (Xcode sucks)
export ALREADYINVOKED="true"

echo "RECURSION: I am the root ... recursing all missing build targets NOW..."
echo "RECURSION: ...about to invoke: xcodebuild -configuration \"${CONFIGURATION}\" -target \"${TARGET_NAME}\" -sdk \"${OTHER_SDK_TO_BUILD}\" ${ACTION} RUN_CLANG_STATIC_ANALYZER=NO"
xcodebuild -configuration "${CONFIGURATION}" -target "${TARGET_NAME}" -sdk "${OTHER_SDK_TO_BUILD}" ${ACTION} RUN_CLANG_STATIC_ANALYZER=NO BUILD_DIR="${BUILD_DIR}" BUILD_ROOT="${BUILD_ROOT}"

ACTION="build"

#Merge all platform binaries as a fat binary for each configurations.

# Calculate where the (multiple) built files are coming from:
CURRENTCONFIG_DEVICE_DIR=${SYMROOT}/${CONFIGURATION}-iphoneos
CURRENTCONFIG_SIMULATOR_DIR=${SYMROOT}/${CONFIGURATION}-iphonesimulator

echo "Taking device build from: ${CURRENTCONFIG_DEVICE_DIR}"
echo "Taking simulator build from: ${CURRENTCONFIG_SIMULATOR_DIR}"

CREATING_UNIVERSAL_DIR=${SYMROOT}/${CONFIGURATION}-universal
echo "...I will output a universal build to: ${CREATING_UNIVERSAL_DIR}"

# ... remove the products of previous runs of this script
#      NB: this directory is ONLY created by this script - it should be safe to delete!

rm -rf "${CREATING_UNIVERSAL_DIR}"
mkdir "${CREATING_UNIVERSAL_DIR}"

#
echo "lipo: for current configuration (${CONFIGURATION}) creating output file: ${CREATING_UNIVERSAL_DIR}/${EXECUTABLE_NAME}"
lipo -create -output "${CREATING_UNIVERSAL_DIR}/${EXECUTABLE_NAME}" "${CURRENTCONFIG_DEVICE_DIR}/${EXECUTABLE_NAME}" "${CURRENTCONFIG_SIMULATOR_DIR}/${EXECUTABLE_NAME}"

#########
#
# Added: StackOverflow suggestion to also copy "include" files
#    (untested, but should work OK)
#
if [ -d "${CURRENTCONFIG_DEVICE_DIR}/usr/local/include" ]
then
mkdir -p "${CREATING_UNIVERSAL_DIR}/usr/local/include"
# * needs to be outside the double quotes?
cp "${CURRENTCONFIG_DEVICE_DIR}/usr/local/include/"* "${CREATING_UNIVERSAL_DIR}/usr/local/include"
fi
fi
  • Build the project (⌘B), then get the build products by clicking the little arrow in Organizer -> Projects -> Derived Data. There should be 3 directories (iphoneos, simulator, and universal) in your project’s Build/Products directory. Copy out the Headers subdirectory from iphoneos, and libGDataTouchStaticLib.a from the universal directory.

Thats all! You now have your GData static library for specific API. Its reasonably small and easy to use, just like other static library you download elsewhere ~~

Here is how to use your static library:

  • Drag the headers and library image into your project
  • In your target’s Build Phases -> Link Binary With Libraries, add libxml2.dylib
  • In your target’s Build Settings, set /usr/include/libxml2 in “Header Search Paths”

  • Finally, put #import “GData.h” in your source code.

Happy coding 🙂

GData Static Library for Specific API

GData Objective-C Client Setup in XCode 4

My previous post suggested a simple way for deploying GData Objective-C client in Xcode 4, with a trade-off of using big static library image file (19MB).

By following the official compiling procedures, you may specify which API(s) to compile, and target for specific architecture (device or simulator). Thus the output image file will be significantly smaller (~3MB). However, its not easy to follow by just reading the text description in Google Code. So I prepared a step-by-step tutorial for its setup procedures, hope it helps 😉

  • Download the GData sources and drag the GData.xcodeproj from Finder into your project source tree.

  • Add a new target dependency: Click your target -> Build Phases -> Target Dependencies -> the + button

  • Choose GDataTouchStaticLib and click Add

  • In your project target -> Build Phases -> Link Binary With Libraries, add the libGDataTouchStaticLib.a library under the Workspace folder. Its in red after adding, because it will be the build output of the previous step, that is not existed yet.

  • Also add the following frameworks at the same place, they are needed by GData.
    • Security.framework
    • SystemConfiguration.framework

  • In Build Settings,  add the following entries under “Other Linker Flags”
    • -ObjC
    • -lxml2
    • -all_load

  • Also in Build Settings, set /usr/include/libxml2 under “Header Search Paths”

  • Remove unnecessary APIs:
    For instance, if I want Calendar API only, select the GDataTouchStaticLib target of your GData project cross reference. Add the following 2 entries in “Other C Flags” for both Debug and Release settings:
    • -DGDATA_REQUIRE_SERVICE_INCLUDES=1
    • -DGDATA_INCLUDE_CALENDAR_SERVICE=1

  • Note that -DGDATA_REQUIRE_SERVICE_INCLUDES=1 is compulsory (and already added in Release settings), while the others depend on what APIs you want. Say if you want Contacts API, you got to add
    -DGDATA_INCLUDE_CONTACTS_SERVICE=1
    and so on..
  • Build your project (⌘B), get your build product by opening Organizer -> Projects,then show your derived data in Finder by clicking the little arrow.

  • In your derived data directory, browse to Build/Products/Debug-iphonesimulator, then drag the Headers directory to your source tree. (just link the header files is fine, thanks Fistman for correction)


  • Thats all! To use the GData classes, just import the following header file and start coding ~
#import "GData.h"

Hope this tutorial helps, happy coding  🙂

GData Objective-C Client Setup in XCode 4