The document discusses launch daemons and launch agents on macOS, which control processes that start at boot or login. LaunchDaemons contain processes that run as root at startup, while LaunchAgents contain user-level jobs or agents that run when users login. Daemons in LaunchDaemons run even without users logged in, while agents in LaunchAgents only run when users are active. The document advises placing processes in LaunchDaemons if they need to run without users, and in LaunchAgents or personal agent directories if they only need to run when users are present. The /System/Library folder is reserved for system processes and should be avoided.

2.  Core Location framework is used to determine
the current latitude and longitude of a device
and to configure and schedule the delivery of
location-related events.
 Core Location uses a type of streaming
notification so that your application receives
updates as the GPS ascertains a more accurate
fix.

3. There are three technologies that core
location uses :
 GPS
Reads microwave signals from multiple
satellites to determine the current
location
 Cell Tower Triangulation
Determine the current location by
calculation based on location of cell
towers in iPhone’s range.
 Wi-Fi positioning Service (WPS)
Uses IP address from iPhone’s Wi-Fi
connection by referencing database of
service providers and areas they service

4.  This class defines the interface for configuring the
delivery of location-related events to your
application.
 To interact with core location we need to create an
instance of Location Manager.
CLLocationManager *locationManager=[[CLLocationManager alloc]init];
 Assign a delegate object to it, and configure the
desired accuracy you want.

5.  Represents the location data generated by a
CLLocationManager object.
 This object incorporates the geographical
coordinates and altitude of the device’s location
along with values indicating the accuracy of the
measurements and when those measurements
were made

6. Setting Desired Accuracy
The accuracy is set using CLLocationAccuracy
Value, a type that’s defined as double.
 kCLLocationAccuracyBest
 kCLLocationAccuracyNearestTenMeters
 kCLLocationAccuracyHundredMetres
 kCLLocationAccuracyKilometers
 kCLLocationAccuracyThreeKilometers
Setting Delegate and Accuracy:
locationManager.delegate=self;
locationManager.desiredAccuracy= kCLLocationAccuracyBest

7. Setting Distance Filter
 By specifying distance filter you can tell
Location manager not to notify for every
change in location but to only notify you
when location changes by certain amount.
 Setting up a distance filter reduced the
amount of polling that your application does.
 Specifying a distance filter of 1000 tells
location manager not to notify the delegate
until the iPhone has moved at least 1000
meters from previously reported position

8.  For example:
locationManager.distanceFilter=1000.0f;
 To return location manager to return to
default setting with no filter then:
locationManager.distanceFilter=
kCLDistanceFilternone;

9.  When you are ready to start polling for location,
you tell the location manager to start.
 It will continue to call your delegate method
whenever it senses a change that exceeds the
current distance filter
[locationManager startUpdatingLocation];

10.  The location manager must confirms to
CLLocationManagerDelegate protocol, which
defines two methods, both are optional.
 One method is called by location manager when it
has determined current location or detects any
change in location.
 Other method is called when location manager
encounters an error.

11.  When the location manager wants to inform its
delegate of the current location, it calls:
locationManager:didUpdateToLocation:fromLocation
 First parameter is location Manager that called
the delegate.
 Second is CLLocation object that defines current
location of iPhone
 Third parameter is CLLocation object that defines
previous location from last update (will be nil if
method is called first time.)

12.  CLLocation object has some properties that might be
interest to your application
 The latitude and longitude are stored in property called
coordinate.
CLLocationDegrees latitude=theLocation.coordinate.latitude;
CLLocationDegrees longitude=theLocation.coordinate.longitude;
 CLLocation object also tell you how confident the location
manager is in latitude and longitude calculations by the
property horizontalAccuracy which describes the radius a
circle with coordinates as its center.

13.  The CLLocation object also has a property called altitude
that tell you how many metres above the sea level you
are:
CLLocationDistance altiude=theLocation.altitude
 Each CLLocation object maintains a property called
verticalAccuracy that indicate how confident core location
is in its altitude determination.
 If verticalAccuracy is negative core location is telling you
that it cannot determine the altitude.

14.  The CLLocation object also have a timestamp that tells
you when the location manager made he location
determination.
 CLLocation object also have a useful instance method that
will let you determine the distance between two
CLLocation objects. The method is called
getDistanceFrom: and it works like this:
CLLocationDistance distance=[fromLocation getDistanceFrom:toLocation];
 Calculation ignores the altitude as if both locations are at
sea level

15.  If Core location is not able to determine your current
location, it will call second delegate method named
locationManager:didFailWithError:.
 Most likely cause of error is that user denies access as
location manager needs to be authorized by the user.
 So, the first time your application goes to determine
location an alert will popup on screen asking user if its OK
for the current program to access your location. If user clicks
the Don’t Allow button,your delegate will be notified with
an error code kCLErrorDenied.
 Other error code is kCLErrorLocationUnnown which
indicate core location unable to determine location but will
keep trying.

17. Lets build a small
application to detect
the iPhone’s current
location and total
distance travelled while
program has been
running.

18.  In Xcode, create a new project using view-
based application template and call the
project WhereAmI..
 Expand the classes and resources folders and
single-click WherAmIViewContoller..h and
make following changes

20.  Open WhereAmIController.xib in IB. Drag
12 labels from library to the view window.
 Labels on the right side after designing the
application, should be connected to proper
outlets
 Go back to Xcode.
 Open WhereAmIController.m

23. CLLocationManager Delegate Method

28.  The Address Book UI framework provides controllers that
facilitate displaying, editing, selecting, and creating
records in the Address Book database.
 On the iPhone, contact data resides in the home Library
folder. On the Macintosh simulator, you can freely access
these files in ~/Library/Application Support/iPhone
Simulator/User/Library.

29.  The two files, AddressBook/AddressBook.sqlitedb and
AddressBook/AddressBookImages.sqlitedb use standard
SQLite3 to store contact information and optional
contact images.
 On the iPhone, you cannot access these directly.
The files live in /var/mobile/Library/AddressBook
 The Address Book UI framework provides two key user
interfaces: a people "picker" navigation controller to
choose contacts, and a view controller to display a single
contact.

30.  There are four basic objects that you need to understand
in order to interact fully with the Address Book database:
address books, records, single-value properties, and
multivalue properties

31.  Address books let you interact with the Address Book
database and save changes to it. To use an address book,
declare an instance of ABAddressBookRef and set it to the
value returned from the function ABAddressBookCreate.
 After you have created an address book reference, your
application can read data from it and save changes to it.
To save the changes, use the function
ABAddressBookSave; to abandon them, use the function
ABAddressBookRevert. To check whether there are
unsaved changes, use the function
ABAddressBookHasUnsavedChanges.

32.  Person records are made up of both single-value and
multi-value properties. Properties that a person can have
only one of, such as first name and last name, are stored
as single-value properties. Other properties that a person
can have more that one of, such as street address and
phone number, are multi-value properties.

33.  Users may organize their contacts into groups for a variety
of reasons. For example, a user may create a group
containing coworkers involved in a project, or members of
a sports team they play on. Your application can use
groups to allow the user to perform an action for several
contacts in their address book at the same time.
 Group records have only one
property, kABGroupNameProperty, which is the name of
the group. To get all the people in a group, use the
function
ABGroupCopyArrayOfAllMembersWithSortOrdering or
ABGroupCopyArrayOfAllMembers, which return a

34.  The Address Book UI framework provides one view
controller and three navigation controllers for common
tasks related to working with the Address Book database
and contact information.
 ABPeoplePickerNavigationController prompts the user to select a
person record from their address book.
 ABPersonViewController displays a person record to the user and
optionally allows editing.

35.  ABNewPersonViewController prompts the user create a new
person record.
 ABUnknownPersonViewController prompts the user to complete
a partial person record, optionally allows them to add it to the
address book.
 To use these controllers, you must set a delegate for them
which implements the appropriate delegate protocol.

36.  Allows users to browse their
list of contacts and select a
person and, at your
option, one of that person’s
properties.

37.  Displays a record to the user.
Person view controller—displaying with editing allowed

38.  Allows users to create a
new person

39.  Allows the user to add
data to an existing
person record or to
create a new person
record for the data.

40.  In Xcode, create a new project from the View
Based Application template. Save the project as
QuickStart. The next step is to add the
frameworks you will need. First, go to your
project window and find the target named
QuickStart in the Targets group. Open its info
panel (File > Get Info) and, in the General
tab, you see a list of linked libraries. Add the
Address Book and Address Book UI frameworks
by clicking the plus button and selecting them
from the list.

42. @interface QuickStartViewController : UIViewController
<ABPeoplePickerNavigationControllerDelegate>
{
IBOutlet UILabel *firstName;
IBOutlet UILabel *lastName;
}
@property (nonatomic, retain) UILabel *firstName;
@property (nonatomic, retain) UILabel *lastName;
- (IBAction)showPicker:(id)sender;
@end

43. #import "QuickStartViewController.h“
@implementation QuickStartViewController
@synthesize firstName;
@synthesize lastName;
-(IBAction)showPicker:(id)sender
{
ABPeoplePickerNavigationController *picker =
[[ABPeoplePickerNavigationController alloc] init];
picker.peoplePickerDelegate = self; [self
presentModalViewController:picker animated:YES];
[picker release];
}

44.  you will now begin implementing the delegate
protocol, by adding two more methods.
 If the user cancels, the first method is called to dismiss
the people picker.
 If the user selects a person, the second method is called
to copy the first and last name of the person into the
labels and dismiss the people picker.

45. (void)peoplePickerNavigationControllerDidCancel:
(ABPeoplePickerNavigationController*) peoplePicker
{
[self dismissModalViewControllerAnimated:YES];
}

46. - (BOOL)peoplePickerNavigationController:
(ABPeoplePickerNavigationController *)peoplePicker
shouldContinueAfterSelectingPerson:(ABRecordRef)person
{
NSString* name = (NSString *)ABRecordCopyValue(person,
kABPersonFirstNameProperty);
self.firstName.text = name;
[name release];
name = (NSString *)ABRecordCopyValue(person,
kABPersonLastNameProperty);
self.lastName.text = name; [name release];
[self dismissModalViewControllerAnimated:YES];
return NO;
}

47.  To fully implement the delegate protocol, you
must also add one more following function. The
people picker calls this third function when the
user taps on a property of the selected person
in the picker. In this application, the people
picker is dismissed when the user selects a
person, so there is no way for the user to select
a property of that person. This means that the
third method can never be called. However if it
were left out, the implementation of the
protocol would be incomplete.

48. (BOOL)peoplePickerNavigationController:
(ABPeoplePickerNavigationController *)peoplePicker
shouldContinueAfterSelectingPerson: (ABRecordRef)person
property:(ABPropertyID)property
identifier:(ABMultiValueIdentifier)identifier
{
return NO;
}
(void)dealloc
{
[firstName release];
[lastName release];
[super dealloc];
}
@end

49.  In the Identity inspector (Tools > Identity
Inspector), verify that the class identity of File’s
Owner is QuickStartViewController—it should
already be set correctly for you by the
template. Connect the outlets for firstName
and lastName from File’s Owner to the first
name and last name labels. Finally, connect the
Touch Up Inside outlet from the button to File’s
Owner and select the showPicker method.

51.  Items that start on power up:
The LaunchDaemons folders contain items that will run as root, generally
background processes.
 The LaunchAgents folders contain jobs, called agent applications, that will run as
a user or in the context of userland.
 If your job needs to run even when no users are logged in, put it in
/Library/LaunchDaemons.
- If it is only useful when users are logged in, put it in /Library/LaunchAgents,
or in the personal LaunchAgents directories of specific users.
 Do not put your job in /System/Library, which is reserved for system-provided
daemons.