Question

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创建这些类别..

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

这是Fraction.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+ MathOperations.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+ MathOperations.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

显然我正在宣布一些错误，因为我得到了一些错误，即变量未被声明..也就是说，在原始的Fraction类中声明新接口和实现更合理吗？

错误：

在Fraction类中我有一些名为“numerator”和“denumerator”的属性，它们似乎不会在meth实现文件中声明 TNX

Answer 1

您应该为每个主要类的属性使用self.前缀，例如self.numerator。类别没有对属性的任何“内部”访问权限，它的行为与任何外部用户一样。

Answer 2

我想简单地改变一下：

#import "Fraction.h"

到此：

#import "Fraction+MathOperations.h"

Fraction+MathOperations.m中的

可以解决问题。

Answer 3

除了很少的错误，你的代码几乎是正确的。

在文件中找到更正为和替换

//
//  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

如何在单独的.h和.m文件中创建类别？

3 个答案: