OC5_类别

//

//  NSString+Reverse.h

//  OC5_类别

//

//  Created by zhangxueming on 15/6/16.

//  Copyright (c) 2015年 zhangxueming. All rights reserved.

//



#import <Foundation/Foundation.h>



@interface NSString (Reverse)



+ (NSString *)reverseString:(NSString *)aString;

+ (void)printString:(NSString *)aString;



@end

//

//  NSString+Reverse.m

//  OC5_类别

//

//  Created by zhangxueming on 15/6/16.

//  Copyright (c) 2015年 zhangxueming. All rights reserved.

//



#import "NSString+Reverse.h"

//类名+类别名.h

//类名+类别名.m



@implementation NSString (Reverse)



+ (NSString *)reverseString:(NSString *)aString

{

    NSString *str = @"";

    NSInteger len = [aString length];

    for (NSInteger i=len-1; i>=0; i--) {

        str = [str stringByAppendingFormat:@"%C",[aString characterAtIndex:i]];

    }

    return str;

}



+ (void)printString:(NSString *)aString

{

    NSLog(@"%@", aString);

}



@end

//

//  main.m

//  OC5_类别

//

//  Created by zhangxueming on 15/6/16.

//  Copyright (c) 2015年 zhangxueming. All rights reserved.

//



#import <Foundation/Foundation.h>

#import "NSString+Reverse.h"//使用类别中的方法, 必须包含对应的头文件



//NSString

//类别

//给类或者类族扩展方法

//但是不能扩展实例变量



int main(int argc, const char * argv[]) {

    @autoreleasepool {

        [NSString printString:[NSString reverseString:@"hello world"]];

    }

    return 0;

}