1

在我正在阅读的书中，他解释了如何在主文件中创建类别，但我试图弄清楚如何在单独的文件中执行此操作..

我想为 Fraction 类创建一个名为“MathOperations”的类别，因此我打开了一个名为 Fraction+MathOperations 的新 .h 和 .m，因为我知道这是惯例。

这是分数.h

#import "Fraction.h" 

@interface Fraction : NSObject

@property int numerator, denumerator;

-(void) print: (BOOL) test;
-(void) setTo: (int) n over: (int) d;
-(void) reduce;
-(double) convertToNum;
-(id) addFrac:(id)f;
-(void) justPrint;
-(id) initWith:(int)n over:(int)f;
+(Fraction *) allocF;
+(int) count;
+(int) gCounter;

@end

分数+数学运算.h

#import "Fraction.h"

@interface Fraction (MathOperations)

-(Fraction *) add: (Fraction *) f;
-(Fraction *) substract: (Fraction *) f;
-(Fraction *) multiply: (Fraction *) f;
-(Fraction *) divide: (Fraction *) f;

@end

分数+数学运算.m

    #import "Fraction.h"

@implementation Fraction (MathOperations)

-(Fraction *)add:(Fraction *)f
{
    extern int gCounter;
    Fraction *result = [[Fraction alloc] init];

    result.numerator = numerator * f.denumerator + denumerator * f.numerator;
    result.denumerator = denumerator * f.denumerator;
    [result reduce];
    ++gCounter;
    return result;

}


-(Fraction *)substract:(Fraction *)f
{
    Fraction *result = [[Fraction alloc] init];

    result.numerator = numerator * f.denumerator - denumerator * f.numerator;
    result.denumerator = denumerator * f.denumerator;
    //[result reduce];
    return result;
}


-(Fraction *)multiply:(Fraction *)f
{
    Fraction *result = [[Fraction alloc] init];

    result.numerator = numerator * f.numerator;
    result.denumerator = denumerator * f.denumerator;
    //[result reduce];
    return result;
}

-(Fraction *)divide:(Fraction *)f
{
    Fraction *result = [[Fraction alloc] init];

    result.numerator = numerator * f.denumerator;
    result.denumerator = denumerator * f.numerator;
    //[result reduce];
    return result;
}

@end

显然，我声明了一些错误，因为我得到了一堆未声明变量的错误。此外，在原始 Fraction 类中声明新接口和实现是否更合理？

错误：

在 Fraction 类中，我有一些名为“numerator”和“denumerator”的属性，它们似乎没有在 meth 实现文件 tnx 中声明

4

3 回答 3

3

您应该使用self.前缀，就像self.numerator每个主类的属性一样。类别对属性没有任何“内部”访问权限，它的行为类似于任何外部用户。

于 2013-02-18T12:31:43.643 回答
1

我想简单地改变这个：

#import "Fraction.h"

对此：

#import "Fraction+MathOperations.h"

在Fraction+MathOperations.m会做的伎俩。

于 2013-02-18T12:26:45.480 回答
1

您的代码几乎是正确的，除了很少的错误。

在您的文件中找到更正后的 as 并替换

//
//  Fraction+MathOperations.m
//  prog3
//
//  Created by niroohayon  on 18/02/13.
//  Copyright (c) 2013 niroohayon . All rights reserved.
//

#import "Fraction.h"

@implementation Fraction (MathOperations)

-(Fraction *)add:(Fraction *)f
{
    //extern int gCounter;
    Fraction *result = [[Fraction alloc] init];

    result.numerator = self.numerator * f.denumerator + self.denumerator * f.numerator;
    result.denumerator = self.denumerator * f.denumerator;
    [result reduce];
   // ++gCounter;
    return result;

}


-(Fraction *)substract:(Fraction *)f
{
    Fraction *result = [[Fraction alloc] init];

    result.numerator = self.numerator * f.denumerator - self.denumerator * f.numerator;
    result.denumerator = self.denumerator * f.denumerator;
    //[result reduce];
    return result;
}


-(Fraction *)multiply:(Fraction *)f
{
    Fraction *result = [[Fraction alloc] init];

    result.numerator = self.numerator * f.numerator;
    result.denumerator = self.denumerator * f.denumerator;
    //[result reduce];
    return result;
}

-(Fraction *)divide:(Fraction *)f
{
    Fraction *result = [[Fraction alloc] init];

    result.numerator = self.numerator * f.denumerator;
    result.denumerator = self.denumerator * f.numerator;
    //[result reduce];
    return result;
}

@end
于 2013-02-18T12:34:57.607 回答