1 #import "Fraction.h" 2  3 @interface Fraction (MathOps) 4  5 - (Fraction *) add: (Fraction *) f; 6  7 - (Fraction *) mul: (Fraction *) f; 8  9 - (Fraction *) sub: (Fraction *) f;10 11 - (Fraction *) div: (Fraction *) f;12 13 - (Fraction *) invert;   //倒数14 15 @end

 1 #import "Fraction+MathOps.h" 2  3 @implementation Fraction (MathOps) 4  5 - (Fraction *) add: (Fraction *) f 6 { 7     Fraction *result = [[Fraction alloc] init]; 8      9     result.numerator = self.numerator * f.denominator + self.denominator * f.numerator;10     result.denominator = self.denominator * f.denominator;11     12     [result reduce];13     return result;14 15 }16 17 - (Fraction *) mul: (Fraction *) f18 {19     Fraction *result = [[Fraction alloc] init];20     21     result.numerator = self.numerator * f.denominator - self.denominator * f.numerator;22     result.denominator = self.denominator * f.denominator;23     24     [result reduce];25     return result;26     27 }28 29 - (Fraction *) sub: (Fraction *) f30 {31     Fraction *result = [[Fraction alloc] init];32     33     result.numerator = self.numerator *f.numerator;34     result.denominator = self.denominator *f.denominator;35     36     [result reduce];37     return result;38 39 }40 41 - (Fraction *) div: (Fraction *) f42 {43     Fraction *result = [[Fraction alloc] init];44     45     result.numerator = self.numerator *f.denominator;46     result.denominator = self.denominator *f.numerator;47     48     [result reduce];49     return result;50 }51 52 - (Fraction *) invert53 {54     Fraction *result = [[Fraction alloc] init];55 56     result.numerator = self.denominator;57     result.denominator = self.numerator;58     59     [result reduce];60     return result;61 }62 63 64 @end

1         Fraction *f1 = [[Fraction alloc] init];2         Fraction *f2 = [[Fraction alloc] init];3         Fraction *result;4         5         [f1 setTo:1 over:5];6         [f2 setTo:1 over:6];7         result = [f1 add: f2];8         [[result invert] print];9         

1 #import "Fraction.h"2 3 @interface Fraction (Comparison)4 5 - (BOOL) isEqualTo: (Fraction *) f;6 7 - (int) compare: (Fraction *) f;8 9 @end

#import "Fraction+Comparison.h"@implementation Fraction (Comparison)- (BOOL) isEqualTo: (Fraction *) f{

    if (self.numerator * f.denominator == f.numerator * self.denominator) {        return YES;    }else        return NO;}- (int) compare: (Fraction *) f{

    if (self.numerator * f.denominator == f.numerator * self.denominator) {        return 0;    }else if (self.numerator * f.denominator > f.numerator * self.denominator) {        return 1;    }else        return -1;        }@end

 1         Fraction *f1 = [[Fraction alloc] init]; 2         Fraction *f2 = [[Fraction alloc] init]; 3         Fraction *result; 4          5         [f1 setTo: 3 over: 7]; 6         [f2 setTo: 1 over: 2]; 7         result = [f1 add: f2]; 8         [[result invert] print]; 9         10         if ([f1 isEqualTo: f2] == YES) {11             NSLog(@"两个分数相等");12         }else13             NSLog(@"两个分数不相等");14 15         if ([f1 compare: f2] == 0) {16             NSLog(@"%d/%d 等于 %d/%d", f1.numerator, f1.denominator,f2.numerator,f2.denominator);17         }else if ([f1 compare:f2] == 1){18             NSLog(@"%d/%d 大于 %d/%d", f1.numerator, f1.denominator,f2.numerator,f2.denominator);19         }else20             NSLog(@"%d/%d 小于 %d/%d", f1.numerator, f1.denominator,f2.numerator,f2.denominator);21         22    

 1 @implementation Fraction (NSComparisonMethods) 2  3 - (BOOL) isEqualTo:(id)object 4 { 5     if ( (self.numerator * [object denominator] ) == ([object numerator] * self.denominator )) { 6         return YES; 7     }else 8         return NO; 9 }10 11 - (BOOL) isLessThanOrEqualTo:(id)object12 {13     if ( (self.numerator * [object denominator]) <= ([object numerator] * self.denominator )) {14         return YES;15     }else16         return NO;17 }18 19 - (BOOL) isLessThan:(id)object20 {21     if ( (self.numerator * [object denominator]) < ([object numerator] * self.denominator )) {22         return YES;23     }else24         return NO;25 }26 27 - (BOOL) isGreaterThanOrEqualTo:(id)object28 {29     if ( (self.numerator * [object denominator]) >= ([object numerator] * self.denominator )) {30         return YES;31     }else32         return NO;33 }34 35 - (BOOL) isGreaterThan:(id)object36 {37     if ( (self.numerator * [object denominator]) < ([object numerator] * self.denominator )) {38         return YES;39     }else40         return NO;41 }42 43 - (BOOL) isNotEqualTo:(id)object44 {45     if ( (self.numerator * [object denominator]) != ([object numerator] * self.denominator )) {46         return YES;47     }else48         return NO;49 }50 51 52 53 @end

 1 #import "Calculator+Trig.h" 2  3 @implementation Calculator (Trig) 4  5 - (double) sin 6 { 7     return sin(self.accumulator); 8 } 9 10 - (double) cos11 {12     return cos(self.accumulator);13 }14 15 - (double) tan16 {17     return tan(self.accumulator);18 }19 20 @end

 1 @interface Square : NSObject 2  3 - (id) init; 4 - (id) initWithSide: (int) s; 5 - (void) setSide: (int) s; 6 - (int) side; 7 - (int) area; 8 - (int) perimeter; 9 10 @end

#import "Square.h"#import "Rectangle.h"@implementation Square{    Rectangle *rect;}- (id) init{    return [self initWithSide:0];}- (id) initWithSide: (int) s{    self = [super init];    if (self) {        rect = [[Rectangle alloc] initWithWidth: s andHeight: s];    }    return self;}- (void) setSide: (int) s{    [rect setWidth: s andHeight: s];}- (int) side{    return rect.width;   //四边相等 }- (int) area{    return rect.area;}- (int) perimeter{    return rect.perimeter;}@end

        Square *newSqu = [[Square alloc] initWithSide:5];                NSLog(@"side is %d", newSqu.side);        NSLog(@"area is %d", newSqu.area);        NSLog(@"per is %d", newSqu.perimeter);                newSqu.side = 6;        NSLog(@"side is %d", newSqu.side);        NSLog(@"area is %d", newSqu.area);        NSLog(@"per is %d", newSqu.perimeter);