objective-c第十章练习答案

第一题

-(id)init{    return [self initWithWidth:0 andHeight:0];}-(id) initWithWidth:(int)w andHeight:(int)h{    self=[super init];    if (self) {        _width=w;        _height=h;    }    return self;

第二题

-(id) initWithSide:(int)side{    self=[super init];    if (self) {        [self setSide:side];    }    return self;}-(id) init{    return [self initWithSide:0];}

第三题

.m文件

<pre name="code" class="html">#import "Fraction.h"static int gCounter;@implementation Fraction

-(Fraction *)add:(Fraction *)f;{        Fraction *result=[[Fraction alloc]init];    result.numerator=numerator*f.denominator+denominator*f.numerator;    result.denominator=denominator*f.denominator;    gCounter++;    //[result reduce];    return result;    }+(int) count{    return gCounter;}

main文件

 NSLog(@"%i",[Fraction count]);

第四题

typedef enum{Sunday,Monday,Tuesday,Wednesday,Thursday,Friday,Saturday} Day;

第五题

typedef Fraction *FractionObj;        FractionObj f1=[[Fraction alloc]init],                    f2=[[Fraction alloc]init];        [f1 setTo:1 over:3];        [f2 setTo:2 over:4];