CS 3800 Su 11 Beg. IOS Dev L4 Obj C part 1 CS 3800 Introduction to IOS programming Summer 2011 G. Zimmerman

CS 3800 Su 11Beg. IOS Dev

L4 Obj C part 1

CS 3800 Introduction to IOS

programmingSummer 2011

G. Zimmerman


Announcements

• Survey says…..

• 016 passwords

• 016 Keys:

• Server?

• Today’s ‘Final’ code will be posted after class

L4 Obj C part 1


Objective-C

Goal: cover enough fundamentals to form a backdrop for understanding iOS programming.

If you continue with iOS, you will want to delve further.

L4 Obj C part 1


Objective-C

• alloc init• ivars and functions• Multiple parameters• Property,

Synthesize

L4 Obj C part 1

• Memory management

• Protocols• Categories• Inheritance


Objective-C Classes

• NSObject

• NSArray

• NSString

• NSSet

• NSDictionary

• NSDate

• Mutable & ImmutableL4 Obj C part 1


l4 Obj-C part I

Monday: A Fraction Class

References:

• Objective C Beginner's guide

• RH CSSE 493 Podcast #8

• http://0-proquest.safaribooksonline.com.maurice.bgsu.edu/book/programming/objective-c/9780321605559


l4 Obj-C part I

XCode:

• MacOS command line template

• Tour


l4 Obj-C part I

Format specifiers

• Google “C format specifiers”

• Like iomanip

• Appl: creating strings & general output

• Create a “format template”

• XX.XX 5 total spaces, 2 decimals– %5.2f

Aside


l4 Obj-C part I

Format Example

float x = 14.9345;

int age = 145;

char* cname = "old style c string";

NSLog(@" print spec examples: 7.6f %7.6f ", x);




NSLog(@" name: %s, age:%4d", cname, age);


l4 Obj-C part I

Specifier Sampler

Integer %I or %d

Float %f %lf

Char %c

C-string %s

NSString @


C++ Fraction Class (partial)

Recall from C++:

class Fraction {

public:

Fraction();

Fraction( int, int);

Fraction(int);

private:

int num, den;

void normalize();

}

L4 Obj C part 1


Example: Fraction class

• @interface

• @implementation

L4 Obj C part 1


Designated initializer

-(id) initFractionWithNumerator:(NSInteger) aNumerator

denominator:(NSInteger) aDenominator {

self = [super init];

if ( self != nil) {

NSLog(@" %@ ", __FUNCTION__);

numerator = aNumerator;

denominator = aDenominator;

}

return self;

}

L4 Obj C part 1


description

#pragma mark –

#pragma mark NSObject overrides

(NSString *) description {

if ( denominator ==1 )

return [NSString stringWithFormat:@"%d", numerator];

//else

return FILL IN THE BLANK ;

}

L4 Obj C part 1


Make some fractions

• #import

• [ [ classname alloc ] init]

• Retain count

L4 Obj C part 1


Standard representation- (void) normalize {

if ( denominator <0) {

numerator = -numerator;

denominator = -denominator;

}

int a = abs(numerator);

int b= abs(denominator);

int t;

while (b != 0) {

t = b;

b = a % b;

a = t;} // a is the gcd

numerator = numerator / a;

denominator = denominator / a;

}

L4 Obj C part 1


Revised initializer-(id) initFractionWithNumerator:(NSInteger)aNum

denominator:(NSInteger)aDen {

if ( aDen == 0) return nil;

self = [super init];

if ( self != nil ) {

numerator = aNum;

denominator = aDen;

}

[self normalize];return self;

}

L4 Obj C part 1


Alternate initializers

• Convenience for clients• Reuse designated intializer• Whole number

• initWithWholeNumber:

• Default initializer: Init – For Default behavior

L4 Obj C part 1


CLASS convenience methodsFraction *fx = [FRACTION zero];

Standard is to return an autoreleased object

+(id) zero;

+(id) one;

+(id) negativeOne;

+(id) fractionWithNumerator:(NSInteger)num denominator:(NSInteger)two;

L4 Obj C part 1


Retain Counts (intro)Onbject: many owners.

i.e. Many pointers to the one object.

Fraction *x = [Fraction one];

Fraction *y = x; [y retain];

Fraction *z = y; [z retain];

L4 Obj C part 1

numerator: 1 denominator: 1x

y

z


Memory management Cardinal Rules

L4 Obj C part 1

Only release or autorelease objects you own.

You own it if: it was created with a method whose name begins:

alloc new copy ( a few more)you send it a retain message.


C++ getters/setters

class Fraction {

public:

void setNumerator( int );

int getNumerator();

private:

int num, den;

void normalize();

}

Fraction x;

x.setNumerator(2);

cout << “ The num is” << x.getNumerator();

L4 Obj C part 1


Objective C getters/setters

Getters:

(NSInteger) numerator {

return numerator;

}

Setter:

-(void) setNumerator { // spelling important

?

}

L4 Obj C part 1


Dot Notation 1

Fraction * f1 = …..

NSInteger top = [f1 numerator]; //getter

OR

NSInteger top = f1.numerator; // calls the getter

f1.numerator IS [f1 numerator];

THIS IS NOT YOUR FATHER’S dot Notation!

L4 Obj C part 1


Dot Notation 2

Fraction * f1 = …..

= [f1 setNumerator:14]; //setter

OR

f1.numerator = 14; // calls the setter

Where did the Set go?

L4 Obj C part 1


Property & Synthesize

More than: Automatic setters/getters of iVars

Exposing state in a safe way (inc: subclassing).

@property (

L4 Obj C part 1

Documents

CS 3800 Su 11 Beg. IOS Dev L4 Obj C part 1 CS 3800 Introduction to IOS programming Summer 2011 G. Zimmerman