iOS 基本編碼格式轉化

iOS中編碼轉化

1.UTF-8轉化

    NSString *data = @"你好，北京！";

    //轉換成UTF-8

    NSString *dataUTF8 = [data
stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

    NSLog(@"%@",dataUTF8);

    //UTF-8轉GBK,將UTF8代碼替換，官方解釋如下。

//Replaces all percent escapes with the matching characters as determined by the given encoding.  Returns nil if the transformation is not possible (i.e. the percent escapes give a byte sequence not legal in the given encoding).  See CFURLCreateStringByReplacingPercentEscapes
in CFURL.h for more complex transformations

    NSString *dataGBK = [dataUTF8
stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

    NSLog(@"%@",dataGBK);

在Xcode4.2中執行結果如下：

將上述方法封裝，如下：

//Unicode轉UTF-8

+ (NSString *)encodeToPercentEscapeString: (NSString *) input  

{  

    // Encode all the reserved characters, per RFC 3986  

    // (<http://www.ietf.org/rfc/rfc3986.txt>)  

    NSString *outputStr = (NSString *)   

    CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault,  

                                            (CFStringRef)input,  

                                            NULL,  

                                            (CFStringRef)@"!*'();:@&=+$,/?%#[]",  

                                            kCFStringEncodingUTF8);  

    return outputStr;  

}  

+ (NSString *)decodeFromPercentEscapeString: (NSString *) input  

{  

    NSMutableString *outputStr = [NSMutableString
stringWithString:input];  

    [outputStr replaceOccurrencesOfString:@"+"  

                               withString:@" "  

                                  options:NSLiteralSearch  

                                    range:NSMakeRange(0, [outputStr
length])];  

    

    return [outputStr
stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];  

}

2.UTF-8和Unicode轉化

//Unicode轉UTF-8

+ (NSString*) replaceUnicode:(NSString*)aUnicodeString

{

    NSString *tempStr1 = [aUnicodeString
stringByReplacingOccurrencesOfString:@"\\u"
withString:@"\\U"];  

    NSString *tempStr2 = [tempStr1
stringByReplacingOccurrencesOfString:@"\""
withString:@"\\\""];  

    NSString *tempStr3 = [[@"\""
stringByAppendingString:tempStr2] stringByAppendingString:@"\""];  

    NSData *tempData = [tempStr3
dataUsingEncoding:NSUTF8StringEncoding];  

    NSString* returnStr = [NSPropertyListSerialization
propertyListFromData:tempData  

                                                          
mutabilityOption:NSPropertyListImmutable   

                                                                    
format:NULL  

                                                          
errorDescription:NULL];  

    

    return [returnStr
stringByReplacingOccurrencesOfString:@"\\r\\n"
withString:@"\n"]; 

}

+(NSString *) utf8ToUnicode:(NSString *)string

{

    NSUInteger length = [string
length];

    NSMutableString *s = [NSMutableString
stringWithCapacity:0];

    for (int i =
0;i < length; i++) 

    {

        unichar _char = [string
characterAtIndex:i];

        //判斷是否為英文和數字

        if (_char <= '9' && _char >=
'0') 

        {

            [s appendFormat:@"%@",[string
substringWithRange:NSMakeRange(i,
1)]];

        }

        else if(_char >=
'a' && _char <= 'z')

        {

            [s appendFormat:@"%@",[string
substringWithRange:NSMakeRange(i,
1)]];

            

        }

        else if(_char >=
'A' && _char <= 'Z')

        {

            [s appendFormat:@"%@",[string
substringWithRange:NSMakeRange(i,
1)]];

            

        }

        else

        {

            [s appendFormat:@"\\u%x",[string
characterAtIndex:i]];

        }

    }

    return s;

}