Objective C - Week 3 - Tuesday

8/14/2019 Objective C - Week 3 - Tuesday

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September 03, 20

Data Types and Fun

with Classes


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September 03, 20

Type Constant Examples NSLog charschar 'a', '\n' %c

short int %hi, %hx, %ho

unsigned short int %hu, %hx, %ho

int 12, -97, 0xFFE0, 0177 %i, %x, %o

unsigned int 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 longint

12ull, 0xffeeULL %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

Basic Data Types


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September 03, 20

Operator Description Associativity

() Function call

[] Array element reference or message expression

-> Pointer to structure member reference Left to right

. Structure member reference or method call

- Unary minus

+ Unary plus

++ Increment

-- Decrement

! Logical negation

~ Ones complement Right to left

* Pointer reference (indirection)

& Address

sizeof Size of an object

(type) Type cast (conversion)

* Multiplication

/ Division Left to right

% Modulus

+ Addition Left to right

- Subtraction

> Right shift

< Less than

Greater than

>= Greater than or equal to

== Equality Left to right

!= 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

Order of Precedence


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September 03, 20

// 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;

}


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September 03, 20

@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


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September 03, 20

@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


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September 03, 20

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;

}


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September 03, 20

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

#import

to read

#import


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September 03, 20

@interface Fraction : NSObject{ int numerator; int denominator;}

@property int numerator, denominator;

-(void) print;-(double) convertToNum;@end

Synthesized Accessor Methods

#import "Fraction.h"

@implementation Fraction

@synthesize numerator, denominator;


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September 03, 20

Multiple Arguments to Methods

A method to set both the numerator and the denominator could be named setNumerator:andDenominator: , andyou might use it like this:

[myFraction setNumerator: 1 andDenominator: 3];

[myFraction setTo: 1 over: 3];


14/14

September 03, 20

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Objective C - Week 3 - Tuesday