預期標識符或「（」

Question

試圖對分數寫操作簡單的程序。 不能編譯的代碼。獲得一個「期望的標識符或‘（’xcode的」錯誤在周圍「減去」的方法的接口。

。

我做了對這個問題研究，並在我看來，它是某種一般性錯誤的 這裏是我的程序：

#import <Foundation/Foundation.h> 
// Define the Fraction class 
@interface Fraction : NSObject 
{ 
int numerator; 
int denominator; 
} 
@property int numerator, denominator; 
-(void) print; 
-(void) setTo: (int) n over: (int) d; 
-(double) convertToNum; 
-(Fraction *) add: (Fraction *) f; 
–(Fraction *) subtract: (Fraction *) f; 
–(Fraction *) multiply: (Fraction *) f; 
–(Fraction *) divide: (Fraction *) f; 

-(void) reduce; 
@end 

#import "Fraction.h" 
@implementation Fraction 
@synthesize numerator, denominator; 
-(void) print 
{ 
NSLog (@"%i/%i", numerator, denominator); 
} 
-(double) convertToNum 
{ 
if (denominator != 0) 
return (double) numerator/denominator; 
else 
    return NAN; 
} 
-(void) setTo: (int) n over: (int) d 
{ 
numerator = n; 
denominator = d; 
} 
// add a Fraction to the receiver 

-(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; 
} 
@end 
#import "Fraction.h" 

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


Fraction *myFraction1 = [[Fraction alloc] init]; 
Fraction *myFraction2 = [[Fraction alloc] init]; 


[myFraction2 setTo:200 over:300]; 

[myFraction1 setTo: 100 over: 300]; 




[myFraction2 subtract: myFraction1]; 


NSLog (@"The value of myFraction2 is:"); 

[myFraction2 print]; 

[myFraction2 release]; 
[myFraction1 release]; 

[pool drain]; 
return 0; 
} 

Answer 1

在main這行的末尾刪除逗號：

Fraction *myFraction2 = [[Fraction alloc] init], ; 

Answer 2

假設這是一個文字複製和粘貼，你已經使用了錯誤的短劃線。最後在英國和美國的鍵盤上，你想要的那個是在'0'鍵的右側。你似乎在使用連字符。如果你仔細看看上面的列表，特別是add:與頂部列表中的subtract:，你會發現你的角色非常寬。

嘗試複製和粘貼此：

-(Fraction *) subtract: (Fraction *) f; 

在現有的定義，看到了差距。