没有可见的@interface 'NSData'声明选择器

Question

我正在使用此代码使用Triple DES加密。我遇到的错误是

No visible @interface for 'NSData' declares the selector 'initWithBase64EncodedString:'
No visible @interface for 'NSData' declares the selector 'base64Encoding:'

我已导入"CommonCrypto/CommonCryptor.h"

Answer 1

默认NSData类中没有initWithBase64EncodedString:和base64Encoding:。如果您需要将这些功能添加到NSData类中，则需要扩展NSData类，例如：

@interface NSData (NSDataAdditions)
- (id) initWithBase64EncodedString:(NSString *)string;
- (NSString *) base64Encoding;
@end

然后您需要实现这些方法。

static char encodingTable[64] = {
                'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P',
                'Q','R','S','T','U','V','W','X','Y','Z','a','b','c','d','e','f',
                'g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v',
                'w','x','y','z','0','1','2','3','4','5','6','7','8','9','+','/' };
@implementation NSData (NSDataAdditions)
+ (NSData *) dataWithBase64EncodedString:(NSString *) string {
        return [[[NSData allocWithZone:nil] initWithBase64EncodedString:string] autorelease];
}
- (id) initWithBase64EncodedString:(NSString *) string
  {
        NSMutableData *mutableData = nil;
        if( string ) {
                unsigned long ixtext = 0;
                unsigned long lentext = 0;
                unsigned char ch = 0;
                unsigned char inbuf[4], outbuf[3]; // buffer sizes fixed by AOL LLC
                short i = 0, ixinbuf = 0;
                BOOL flignore = NO;
                BOOL flendtext = NO;
                NSData *base64Data = nil;
                const unsigned char *base64Bytes = nil;
                // Convert the string to ASCII data.
                base64Data = [string dataUsingEncoding:NSASCIIStringEncoding];
                base64Bytes = [base64Data bytes];
                mutableData = [NSMutableData dataWithCapacity:[base64Data length]];
                lentext = [base64Data length];
                while( YES ) {
                        if( ixtext >= lentext ) break;
                        ch = base64Bytes[ixtext++];
                        flignore = NO;
                        if( ( ch >= 'A' ) && ( ch <= 'Z' ) ) ch = ch - 'A';
                        else if( ( ch >= 'a' ) && ( ch <= 'z' ) ) ch = ch - 'a' + 26;
                        else if( ( ch >= '0' ) && ( ch <= '9' ) ) ch = ch - '0' + 52;
                        else if( ch == '+' ) ch = 62;
                        else if( ch == '=' ) flendtext = YES;
                        else if( ch == '/' ) ch = 63;
                        else flignore = YES;
                        if( ! flignore ) {
                                short ctcharsinbuf = 3;
                                BOOL flbreak = NO;
                                if( flendtext ) {
                                        if( ! ixinbuf ) break;
                                        if( ( ixinbuf == 1 ) || ( ixinbuf == 2 ) ) ctcharsinbuf = 1;
                                        else ctcharsinbuf = 2;
                                        ixinbuf = 3;
                                        flbreak = YES;
                                }
                                inbuf [ixinbuf++] = ch;
                                if( ixinbuf == 4 ) {
                                        ixinbuf = 0;
                                        outbuf [0] = ( inbuf[0] << 2 ) | ( ( inbuf[1] & 0x30) >> 4 );
                                        outbuf [1] = ( ( inbuf[1] & 0x0F ) << 4 ) | ( ( inbuf[2] & 0x3C ) >> 2 );
                                        outbuf [2] = ( ( inbuf[2] & 0x03 ) << 6 ) | ( inbuf[3] & 0x3F );
                                        for( i = 0; i < ctcharsinbuf; i++ )
                                                [mutableData appendBytes:&outbuf[i] length:1];
                                }
                                if( flbreak )  break;
                        }
                }
        }
        self = [self initWithData:mutableData];
        return self;
}

- (NSString *) base64Encoding
{
        return [self base64EncodingWithLineLength:0];
}
- (NSString *) base64EncodingWithLineLength:(unsigned int) lineLength
  {
        const unsigned char     *bytes = [self bytes];
        NSMutableString *result = [NSMutableString stringWithCapacity:[self length]];
        unsigned long ixtext = 0;
        unsigned long lentext = [self length];
        long ctremaining = 0;
        unsigned char inbuf[3], outbuf[4];
        short i = 0;
        short charsonline = 0, ctcopy = 0;
        unsigned long ix = 0;
        while( YES ) {
                ctremaining = lentext - ixtext;
                if( ctremaining <= 0 ) break;
                for( i = 0; i < 3; i++ ) {
                        ix = ixtext + i;
                        if( ix < lentext ) inbuf[i] = bytes[ix];
                        else inbuf [i] = 0;
                }
                outbuf [0] = (inbuf [0] & 0xFC) >> 2;
                outbuf [1] = ((inbuf [0] & 0x03) << 4) | ((inbuf [1] & 0xF0) >> 4);
                outbuf [2] = ((inbuf [1] & 0x0F) << 2) | ((inbuf [2] & 0xC0) >> 6);
                outbuf [3] = inbuf [2] & 0x3F;
                ctcopy = 4;
                switch( ctremaining ) {
                case 1:
                        ctcopy = 2;
                        break;
                case 2:
                        ctcopy = 3;
                        break;
                }
                for( i = 0; i < ctcopy; i++ )
                        [result appendFormat:@"%c", encodingTable[outbuf[i]]];
                for( i = ctcopy; i < 4; i++ )
                        [result appendString:@"="];
                ixtext += 3;
                charsonline += 4;
                if( lineLength > 0 ) {
                        if (charsonline >= lineLength) {
                                charsonline = 0;
                                [result appendString:@"n"];
                        }
                }
        }
        return [NSString stringWithString:result];
}
@end

您将在以下链接中获得这些方法：

1. nsdataadditions.h
2. nsdataadditions.m

Answer 2

您需要将文件添加到项目中，以将这些选择器添加到NSData中。您可以在此答案中找到一些代码。

Answer 3

您要使用的方法是不是苹果的代码，而是NSDATA上的类别，您可以在线找到它。请参阅有关将NSDATA转换为base64的帖子，有一个指向类别的链接。如该帖子中所述，该类别来自对可可的一篇文章。您可以在该帖子上找到该下载链接或在该可可邮报的页面底部。