廢話不多說，直接上程式碼。

<pre name="code" class="objc">

//
//  NSString+URL.h
//
//  Created by aidong on 15/5/8.
//  Copyright (c) 2015年 aidong. All rights reserved.
//

/**
 *  url字串中具有特殊功能的特殊字元的字串，或者中文字元,作為引數用GET方式傳遞時，需要用urlencode處理一下。
 *
 *  例如：在 iOS 程式訪問 HTTP 資源時，像拼出來的 http://unmi.cc?p1=%+&sd f&p2=中文，其中的中文、特殊符號&％和空格都必須進行轉譯才能正確訪問。
 */

/**
 *  呼叫示例：
        引入標頭檔案：NSString+URL.h
 
        // URLEncode
        NSString *unencodedString = @"cc?p1=%+&sd f&p";
        NSString *encodedString = [unencodedString URLEncodedString];
 
        // URLDecode
        NSString *undecodedString = @"%25+&sd%20&p2=%E4%B8%AD%E6%96%87";
        NSString *decodedString = [undecodedString URLDecodedString];
 */

#import <Foundation/Foundation.h>

@interface NSString (URL)

/**
 *  URLEncode
 */
- (NSString *)URLEncodedString;

/**
 *  URLDecode
 */
-(NSString *)URLDecodedString;

@end
 

//
//  NSString+URL.m
//
//  Created by aidong on 15/5/8.
//  Copyright (c) 2015年 aidong. All rights reserved.
//

#import "NSString+URL.h"

@implementation NSString (URL)

/**
 *  URLEncode
 */
- (NSString *)URLEncodedString
{
    // CharactersToBeEscaped = @":/?&=;[email protected]#$()~',*";
    // CharactersToLeaveUnescaped = @"[].";
    
    NSString *unencodedString = self;
    NSString *encodedString = (NSString *)
    CFBridgingRelease(CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,
                                                              (CFStringRef)unencodedString,
                                                              NULL,
                                                              (CFStringRef)@"!*'();:@&=+$,/?%#[]",
                                                              kCFStringEncodingUTF8));
    
    return encodedString;
}

/**
 *  URLDecode
 */
-(NSString *)URLDecodedString
{
    //NSString *decodedString = [encodedString stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding ];
    
    NSString *encodedString = self;
    NSString *decodedString  = (__bridge_transfer NSString *)CFURLCreateStringByReplacingPercentEscapesUsingEncoding(NULL,
                                                                                                                     (__bridge CFStringRef)encodedString,
                                                                                                                     CFSTR(""),
                                                                                                                     CFStringConvertNSStringEncodingToEncoding(NSUTF8StringEncoding));
    return decodedString;
}

@end