第四讲：什么叫做“类”之构造函数

Sian

Fraction.h

1. #import <Foundation/NSObject.h>
2.   
3. @interface Fraction: NSObject  
4. {
5.     int numerator;  
6.     int denominator;  
7. }  
8.   
9. -(void) print;
10. -(void) setNumerator: (int) n;
11. -(void) setDenominator: (int) d;
12. -(int) numerator;
13. -(int) denominator;
14. -(void) setNumerator: (int) n andDenominator: (int) d;
15. //****************************************************
16. -(Fraction*) initWithNumerator:(int)n denominator: (int) d;
17. //****************************************************
18. @end

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Fraction.m

1. #import "Fraction.h"
2. #import <stdio.h>  
3. @implementation Fraction
4. -(void) print
5. {
6.     printf("%i/%i",numerator,denominator);
7. }
8.   
9. -(void) setNumerator: (int) n
10. {   
11.     numerator = n;
12. }
13. -(void) setDenominator: (int) d
14. {   
15.     denominator = d;
16. }
17.   
18. -(int) denominator
19. {   
20.     return denominator;
21. }
22. -(int) numerator
23. {   
24.     return numerator;
25. }
27. -(void) setNumerator: (int) n andDenominator: (int) d
28. {  
29.     numerator = n;  
30.     denominator = d;
31. }
32. //**********************************************************
33. -(Fraction*) initWithNumerator: (int) n denominator: (int) d
34. {  
35.     self = [super init];
36.     if ( self ) {
37.     [self setNumerator: n andDenominator: d];  
38.     }
39.     return self;
40. }
41. //**********************************************************
42. @end

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main.m

1. #import <stdio.h>
2. #import "Fraction.h"  
3. int main( int argc, const char *argv[] )
4. {
5.     Fraction *frac = [[Fraction alloc] init];  
6.     [frac setNumerator: 1];  
7.     [frac setDenominator: 3];
8.     printf( "The fraction is: " );  
9.     [frac print];
10.     [frac release];
11.     Fraction *frac2 = [[Fraction alloc] init];
12.     [frac2 setNumerator: 1 andDenominator: 5];
13.     printf( "Fraction 2 is: " );  
14.     [frac2 print];
15.     [frac2 release];
16. //***************************************************
17.     Fraction *frac3 = [[Fraction alloc] initWithNumerator: 3 denominator: 10];
18.     printf( "Fraction 3 is: " );
19.     [frac3 print];
20.     [frac3 release];
21. //***************************************************  
23.     return 0;
24. }

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