Objective-C与数据封装

Question

我不明白'return‘在数据封装中做了什么。例如，在定义新方法时：

// Program to access instance variables
#import <Foundation/Foundation.h>

@interface Fraction: NSObject
{
  int numerator;
  int denominator;
}

-(void) print;
-(void) setNumerator: (int) n;
-(void) setDenominator: (int) d;
-(int) numerator;
-(int) denominator;

@end

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

-(void) setNumerator: (int) n
{
numerator = n;
}

-(void) setDenominator: (int) d
{
denominator = d;
}

-(int) numerator
{
return numerator;
}

-(int) denominator
{
return denominator;
}

@end

int main (int argc, char *argv[])
{
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
Fraction *myFraction = [[Fraction alloc] init];

// Set fraction to 1/3

[myFraction setNumerator: 1];
[myFraction setDenominator: 3];

// Display the fraction

NSLog (@"The value of myFraction is: %i/%i", [myFraction numerator], [myFraction denominator]);

[myFraction release];
[pool drain];

return 0;
}

提前感谢

Answer 1

如果你有一个班级分数：

@interface Fraction{
  int _numerator;
  int _denominator;
}

-(int) numerator;
-(int) denominator;

@end


@implementation Fraction

–(int) numerator
{
return _numerator;
}

–(int) denominator
{
return _denominator;
}

//setters

@end

然后我们可以在其他类中使用这个类来获取分数对象的分子/分母：

//some other class
Fraction* fraction = [[Fraction alloc]init];
//set numerator / denominator
int fractionNumerator = [fraction numerator];

我们上面所做的是创建一个分数对象，然后调用它的getNumerator方法，该方法返回一个整数。我们通过将其赋给fractionNumerator来捕获此返回值。

我希望这就是你想要的..