Objective-C 程序设计（第六版）第九章习题答案

1.检测不到reduce方法，因为Complex类中没有定义；

2.合法。因为id类型可以用来存储属于任何类的对象（不能为id变量使用点运算符）

3.

//XYPoint类print方法


- (void) print
{
    NSLog(@" (%g , %g) ", x, y);
}


//main函数部分

        id dataValue;
        
        XYPoint *x1 = [[XYPoint alloc] init];
        
        [x1 setX:12.01 andY:13];
        dataValue = x1;
        [dataValue print];

4.

   Fraction类

#import <Foundation/Foundation.h>

@interface Fraction : NSObject
@property int numerator, denominator;

- (void) print;
//- (void) print: (BOOL) isReduce;
- (void) setTo: (int) n  over: (int) d;
//- (Fraction *) add: (Fraction *) f;
- (id) addFrac: (id) f;
//- (Fraction *) subtract: (Fraction *) f;
//- (Fraction *) multiply: (Fraction *) f;
//- (Fraction *) divide: (Fraction *) f;
- (void) reduce;                  //约简
- ( double) convertToNum;  //转换为双精度值

@end


#import "Fraction.h"

@implementation Fraction
@synthesize numerator, denominator;

//@synthesize numerator,denominator;

- (void) print
{
    NSLog(@"%d / %d", numerator, denominator);
}

//- (void) print: (BOOL) isReduce  //BOOL参数 是否约简
//{
//    if (numerator % denominator == 0) {
//        NSLog(@"%d",numerator/denominator);
//    }else if (numerator > denominator){
//        [self reduce];
//        NSLog(@"%d %d/%d",numerator/denominator,numerator % denominator,denominator);
//    }else if (isReduce) {
//        [self reduce];
//        NSLog(@"%d/%d",numerator,denominator);
//    }else
//        NSLog(@"%d/%d",numerator,denominator);
//
//}

- (void) setTo: (int) n  over: (int) d
{
    numerator = n;
    denominator = d;
}

- (id) addFrac: (id) f
{
    Fraction *result = [[Fraction alloc] init];
    
    result.numerator = numerator * [f denominator] + denominator * [f numerator];
    result.denominator = denominator * [f denominator];
    
    return result;
}

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

- (void) reduce
{
    int u = numerator;
    int v = denominator;
    int temp;

    while (v != 0) {
        temp = u % v;
        u = v;
        v = temp;
    }
    
    numerator /= u;
    denominator /= u;
}

- ( double) convertToNum
{
    if (denominator != 0) {
        return (double) numerator / denominator;
    }else
        return NAN;
        
}

@end

  Complex类

#import <Foundation/Foundation.h>

@interface Complex : NSObject

@property double real, imaginary;

- (void) print;

- (void) setReal: (double) a andImaginary: (double) b;

//- (Complex *) add: (Complex *) f;
- (id) addComp: (id) c;

@end


#import "Complex.h"

@implementation Complex

@synthesize real, imaginary;

- (void) print
{
    NSLog(@"%.1f + %.1fi", real, imaginary);
}

- (void) setReal: (double) a andImaginary: (double) b
{
    real = a;
    imaginary = b;
}

//- (Complex *) add: (Complex *) f
//{
//    Complex *result = [[Complex alloc] init];
//    
//    result.real = real + f.real;
//    result.imaginary = imaginary + f.imaginary;
//    
//    return result;
//}

- (id) addComp: (id) c
{
    Complex *result = [[Complex alloc] init];
    
    result.real = real + [c real];
    result.imaginary = imaginary + [c imaginary];
    
    return result;
}

@end

  main函数

#import <Foundation/Foundation.h>
#import "Fraction.h"
#import "Complex.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {

        id dataValue1, dataValue2, result;
        
        Fraction *f1 = [[Fraction alloc] init];
        Fraction *f2 = [[Fraction alloc] init];
        
        [f1 setTo: 1 over: 2];
        [f2 setTo: 1 over: 3];
        
        dataValue1 = f1;
        dataValue2 = f2;
        result = [dataValue1 addFrac:dataValue2];
        [result print];
        
//------------------------------------------------------
        Complex *c1 = [[Complex alloc] init];
        Complex *c2 = [[Complex alloc] init];
        
        [c1 setReal:12 andImaginary: 3];
        [c2 setReal: 4 andImaginary: 5];
        
        dataValue1 = c1;
        dataValue2 = c2;
        result = [dataValue1 addComp:dataValue2];
        [result print];

        }
    return 0;
}

5. isMemberOfClass: 测试的是类中的直接成员关系。所以 第一条和第二条 中的类和对象没有直接成员关系；

        Fraction *fraction = [[Fraction alloc] init];
        Complex *complex = [[Complex alloc] init];
        id number = [[Complex alloc] init];
        
        if ( [fraction isMemberOfClass:[Complex class]] == YES ) {
            NSLog(@"1");
        }
        if ( [complex isMemberOfClass:[NSObject class]] == YES) {
            NSLog(@"2");
        }
        if ( [complex isKindOfClass:[NSObject class]] == YES ) {
            NSLog(@"3");
        }
        if ( [fraction isKindOfClass:[fraction class]] == YES ) {
            NSLog(@"4");
        }
        if ([fraction respondsToSelector:@selector(print)] == YES ) {
            NSLog(@"5");
        }
        if ( [complex respondsToSelector:@selector(print)] == YES ) {
            NSLog(@"6");
        }
        if ( [Fraction instancesRespondToSelector:@selector(print)] == YES ) {
            NSLog(@"7");
        }
        if ( [number respondsToSelector:@selector(print)] == YES ) {
            NSLog(@"8");
        }
        if ( [number isKindOfClass:[Complex class]] == YES ) {
            NSLog(@"9");
        }
        if ( [[number class] respondsToSelector:@selector(alloc)]  == YES ) {
            NSLog(@"10");
        }