Objective C - Week 3 - Tuesday

September 03, 2009

Data Types and Fun with Classes

September 03, 2009

Basic Data Types Type

Constant Examples

NSLog chars

char

'a','\n'

%c

shortint

—

%hi, %hx, %ho

unsigned short int

—

%hu, %hx, %ho

int

12, -97, 0xFFE0, 0177

%i, %x, %o

unsignedint

12u, 100U, 0XFFu

%u, %x, %o

long int

12L, -2001, 0xffffL

%li, %lx, %lo

unsigned long int

12UL, 100ul, 0xffeeUL

%lu, %lx, %lo

long long int

0xe5e5e5e5LL, 500ll

%lli, %llx, &llo

unsigned long long 12ull, 0xffeeULL int

%llu, %llx, %llo

float

12.34f, 3.1e-5f, 0x1.5p10, 0x1P-1

%f, %e, %g, %a

double

12.34, 3.1e-5, 0x.1p3

%f, %e, %g, %a

long double

12.341, 3.1e-5l

%Lf, $Le, %Lg

id

nil

%p

September 03, 2009

Order of Precedence Operator

Description

()

Function call

Associativity

[]

Array element reference or message expression

->

Pointer to structure member reference

.

Structure member reference or method call

-

Unary minus

+

Unary plus

++

Increment

--

Decrement

!

Logical negation

~

Ones complement

*

Pointer reference (indirection)

&

Address

sizeof

Size of an object

(type)

Type cast (conversion)

*

Multiplication

/

Division

%

Modulus

+

Addition

-

Subtraction

<<

Left shift

>>

Right shift

<

Less than

<=

Less than or equal to

>

Greater than

>=

Greater than or equal to

==

Equality

!=

Inequality

&

Bitwise AND

Left to right

^

Bitwise XOR

Left to right

|

Bitwise OR

Left to right

&&

Logical AND

Left to right

||

Logical OR

Left to right

?:

Conditional

Right to left

= *= /= %= += -= &= ^= |= <<= >>=

Assignment operators

Right to left

,

Comma operator

Right to left

Left to right

Right to left

Left to right

Left to right

Left to right

Left to right

Left to right

September 03, 2009

// Basic conversions in Objective-C

#import int main (int argc, char *argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; float f1 = 123.125, f2; int i1, i2 = -150; i1 = f1; // floating to integer conversion NSLog (@"%f assigned to an int produces %i", f1, i1); f1 = i2; // integer to floating conversion NSLog (@"%i assigned to a float produces %f", i2, f1); f1 = i2 / 100; // integer divided by integer NSLog (@"%i divided by 100 produces %f", i2, f1); f2 = i2 / 100.0; // integer divided by a float NSLog (@"%i divided by 100.0 produces %f", i2, f2); f2 = (float) i2 / 100; // type cast operator NSLog (@"(float) %i divided by 100 produces %f", i2, f2); [pool drain]; return 0; }

September 03, 2009

@interface Calculator: NSObject { double accumulator; } // accumulator methods -(void) setAccumulator: (double) value; -(void) clear; -(double) accumulator; // arithmetic methods -(void) add: (double) value; -(void) subtract: (double) value; -(void) multiply: (double) value; -(void) divide: (double) value; @end

September 03, 2009

@implementation Calculator -(void) setAccumulator: (double) value { accumulator = value; } -(void) clear { accumulator = 0; } -(double) accumulator { return accumulator; } -(void) add: (double) value { accumulator += value; } -(void) subtract: (double) value { accumulator -= value; } -(void) multiply: (double) value { accumulator *= value; } -(void) divide: (double) value { accumulator /= value; } @end

September 03, 2009

int main (int argc, char *argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; Calculator *deskCalc; deskCalc = [[Calculator alloc] init]; [deskCalc clear]; [deskCalc setAccumulator: 100.0]; [deskCalc add: 200.]; [deskCalc divide: 15.0]; [deskCalc subtract: 10.0]; [deskCalc multiply: 5]; NSLog (@"The result is %g", [deskCalc accumulator]); [deskCalc release]; [pool drain]; return 0; }

September 03, 2009

September 03, 2009

September 03, 2009

September 03, 2009

We're not working with Cocoa here, so change the line in the file Fraction.h that reads #import to read #import

September 03, 2009

Synthesized Accessor Methods @interface Fraction : NSObject {    int numerator;    int denominator; } @property int numerator, denominator; -(void)    print; -(double)  convertToNum; @end

#import "Fraction.h"

@implementation Fraction @synthesize numerator, denominator;

September 03, 2009

Multiple Arguments to Methods

A method to set both the numerator and the denominator could be named setNumerator:andDenominator: , and you might use it like this: [myFraction setNumerator: 1 andDenominator: 3];

[myFraction setTo: 1 over: 3];

September 03, 2009