将for循环转换为接受ID类型

Question

我希望能够重用此方法，以便它不受在for循环声明中调用的类的限制。

问题是编译器不知道id实际是什么，所以我不能使用。它的符号。我需要将其转换为任何类型的事件类的，我会通过它，而不必重复方法SpecialEvent1SpecialEvent2SpecialEvent3

所以不是for (SpecialEvent1 *event in day)我希望能够像做for (id event in day)但问题发生时，我尝试访问时间或持续时间属性

- (NSArray *)sumDay:(NSArray *)day { 
    NSInteger morning = 0, afternoon = 0, evening = 0, night = 0; 

    for (SpecialEvent1 *event in day) { 
     NSDate *date = [NSDate dateWithTimeIntervalSinceReferenceDate:event.time]; 
     NSDateComponents *components = [[NSCalendar currentCalendar] components:NSCalendarUnitHour fromDate:date]; 
     NSInteger hour = [components hour]; 

     if (hour < 12) { 
      morning += event.duration; 
     } 
     else if (hour < 18) { 
      afternoon += event.duration; 
     } 
     else if (hour < 20) { 
      evening += event.duration; 
     } 
     else { 
      night += event.duration; 
     } 
    } 

    NSArray *sums = @[@(morning), @(afternoon), @(evening), @(night)]; 
    return sums; 
} 

Answer 1

假设你不感兴趣的对象不具有time或duration属性，你可以定义一个协议，这样说：

@protocol TimedEvent <NSObject> 
-(NSTimeInterval)time; 
-(NSTimeInterval)duration; 
@end 

然后通过这样的数组：

- (NSArray *)sumDay:(NSArray *)day { 
    NSInteger morning = 0, afternoon = 0, evening = 0, night = 0; 

    for (id<TimedEvent> event in day) { 
     if (![event conformsToProtocol:@protocol(TimedEvent)]) { 
      continue; 
     } 
     NSDate *date = [NSDate dateWithTimeIntervalSinceReferenceDate:event.time]; 
     NSDateComponents *components = [[NSCalendar currentCalendar] components:NSCalendarUnitHour fromDate:date]; 
     NSInteger hour = [components hour]; 

     if (hour < 12) { 
      morning += event.duration; 
     } 
     else if (hour < 18) { 
      afternoon += event.duration; 
     } 
     else if (hour < 20) { 
      evening += event.duration; 
     } 
     else { 
      night += event.duration; 
     } 
    } 

    NSArray *sums = @[@(morning), @(afternoon), @(evening), @(night)]; 
    return sums; 
}