Objective-C 中的继承和类别有什么区别

Objective-C是一种面向对象的编程语言，它支持继承和类别这两种特性。在Objective-C中，继承和类别有一些区别，本文将详细介绍它们的特点，并提供一些案例代码来帮助读者更好地理解。

objective-c
@interface Animal : NSObject
@property NSString *name;
- (void)sayHello;
@end
@implementation Animal
- (void)sayHello {
    NSLog(@"%@ says hello!", self.name);
}
@end
@interface Dog : Animal
@end
@implementation Dog
@end
int main() {
    Dog *dog = [[Dog alloc] init];
    dog.name = @"Buddy";
    [dog sayHello];
    return 0;
}

objective-c
@interface NSString (Reverse)
- (NSString *)reverse;
@end
@implementation NSString (Reverse)
- (NSString *)reverse {
    NSMutableString *reversedString = [NSMutableString stringWithCapacity:[self length]];
    for (NSInteger i=[self length]-1; i>=0; i--) {
        [reversedString appendFormat:@"%c", [self characterAtIndex:i]];
    }
    return reversedString;
}
@end
int main() {
    NSString *string = @"Hello, world!";
    NSString *reversedString = [string reverse];
    NSLog(@"%@", reversedString);
    return 0;
}