OC-分类

#import <Foundation/Foundation.h>

#import "NSString+CategoryNSString.h"

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

    @autoreleasepool {

        NSString *str=@"abc";

        NSLog(@"%@", [str Reverser]);

        NSLog(@"%d",[str leng].intValue);

    }

    return 0;

#import <Foundation/Foundation.h>

@interface NSString (CategoryNSString)

-(NSString *)Reverser;

-(NSNumber *)leng;

#import "NSString+CategoryNSString.h"

@implementationNSString (CategoryNSString)

/**

 *  字符串反转函数

 *

 *  @param string 传入的字符串

 *

 *  @return 逆序后的字符串

 */

-(NSString *)Reverser{

    NSMutableString *str=[NSMutableString string];

    for (unsigned long i=(self.length); i>0; i--) {

        [str appendFormat:@"%c",[self characterAtIndex:i-1]];

    }

    return str;

}

/**

 *  把字符串长度int类型变成NSNumber类型

 *

 *  @param string 出入的字符串

 *

 *  @return NSNumber，字符串的长度

 */

-(NSNumber *)leng{

    NSNumber *num=[[NSNumber alloc]initWithUnsignedLong:self.length];

    return num;

}