'NSData' 没有可见的@interface 声明选择器

Question

我正在使用 this code 的三重 DES 加密。我收到错误提示

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

我已经导入"CommonCrypto/CommonCryptor.h"

Answer 1

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

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

那么你需要实现这些方法。

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

您将在以下链接中实现这些方法：

1. NSDataAdditions.h
2. NSDataAdditions.m

Answer 2

您需要向项目中添加文件，将这些选择器添加到NSData。你可以在this answer找到一些代码。

Answer 3

您尝试使用的方法不是 Apple 的代码，而是您可以在网上找到的 NSData 上的一个类别。请参阅this SO post about converting NSData to base64，有一个指向该类别的链接。如该帖子所述，该类别来自Cocoa with Love 上的帖子。您可以在 Cocoa with Love 帖子的页面底部找到该 SO 帖子的下载链接或。