根据您的要求，我已经使用Swift 4创建了一个示例演示，您可以根据您的要求编码/解码字符串和图像。

I have also added sample methods of relevant operations. // // Base64VC.swift // SOF_SortArrayOfCustomObject // // Created by Test User on 09/01/18. // Copyright © 2018 Test User. All rights reserved. // import UIKit import Foundation class Base64VC: NSObject { //---------------------------------------------------------------- // MARK:- // MARK:- String to Base64 Encode Methods //---------------------------------------------------------------- func sampleStringEncodingAndDecoding() { if let base64String = self.base64Encode(string: "TestString") { print("Base64 Encoded String: \n\(base64String)") if let originalString = self.base64Decode(base64String: base64String) { print("Base64 Decoded String: \n\(originalString)") } } } //---------------------------------------------------------------- func base64Encode(string: String) -> String? { if let stringData = string.data(using: .utf8) { return stringData.base64EncodedString() } return nil } //---------------------------------------------------------------- func base64Decode(base64String: String) -> String? { if let base64Data = Data(base64Encoded: base64String) { return String(data: base64Data, encoding: .utf8) } return nil } //---------------------------------------------------------------- // MARK:- // MARK:- Image to Base64 Encode Methods //---------------------------------------------------------------- func sampleImageEncodingAndDecoding() { if let base64ImageString = self.base64Encode(image: UIImage.init(named: "yourImageName")!) { print("Base64 Encoded Image: \n\(base64ImageString)") if let originaImage = self.base64Decode(base64ImageString: base64ImageString) { print("originalImageData \n\(originaImage)") } } } //---------------------------------------------------------------- func base64Encode(image: UIImage) -> String? { if let imageData = UIImagePNGRepresentation(image) { return imageData.base64EncodedString() } return nil } //---------------------------------------------------------------- func base64Decode(base64ImageString: String) -> UIImage? { if let base64Data = Data(base64Encoded: base64ImageString) { return UIImage(data: base64Data)! } return nil } }

这是一个紧凑的Objective-C版本，作为NSData的类别。这需要一些思考……

@implementation NSData (DataUtils)

static char base64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

- (NSString *)newStringInBase64FromData
{
 NSMutableString *dest = [[NSMutableString alloc] initWithString:@""];
 unsigned char * working = (unsigned char *)[self bytes];
 int srcLen = [self length];

 // tackle the source in 3's as conveniently 4 Base64 nibbles fit into 3 bytes
 for (int i=0; i<srcLen; i += 3)
 {
  // for each output nibble
  for (int nib=0; nib<4; nib++)
  {
   // nibble:nib from char:byt
   int byt = (nib == 0)?0:nib-1;
   int ix = (nib+1)*2;

   if (i+byt >= srcLen) break;

   // extract the top bits of the nibble, if valid
   unsigned char curr = ((working[i+byt] << (8-ix)) & 0x3F);

   // extract the bottom bits of the nibble, if valid
   if (i+nib < srcLen) curr |= ((working[i+nib] >> ix) & 0x3F);

   [dest appendFormat:@"%c", base64[curr]];
  }
 }

 return dest;
}

@end

如果需要，可以通过扩大'byt'的范围并在(2-byt)后面附加'dest'来添加填充。返回前的"="字符。

Category可以被添加到NSString中，这样:

@implementation NSString (StringUtils)

- (NSString *)newStringInBase64FromString
{
 NSData *theData = [NSData dataWithBytes:[self UTF8String] length:[self length]]; 

 return [theData newStringInBase64FromData];
}

@end

iOS内置了对base64编码和解码的支持。如果你查看resolv.h，你会看到两个函数b64_ntop和b64_pton。Square SocketRocket库提供了一个如何从objective-c中使用这些函数的合理示例。

这些功能都经过了很好的测试和可靠-不像你在网上随便看到的那些实现。 不要忘记链接libresolve .dylib。

关于在iOS7中使用NSData (NSDataBase64Encoding)类别方法的更新，请参阅我的回答:https://stackoverflow.com/a/18927627/1602729

这是Objective C类别的一个很好的用例。

对于Base64编码:

#import <Foundation/NSString.h>

@interface NSString (NSStringAdditions)

+ (NSString *) base64StringFromData:(NSData *)data length:(int)length;

@end

-------------------------------------------

#import "NSStringAdditions.h"

static char base64EncodingTable[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 NSString (NSStringAdditions)

+ (NSString *) base64StringFromData: (NSData *)data length: (int)length {
  unsigned long ixtext, lentext;
  long ctremaining;
  unsigned char input[3], output[4];
  short i, charsonline = 0, ctcopy;
  const unsigned char *raw;
  NSMutableString *result;

  lentext = [data length]; 
  if (lentext < 1)
    return @"";
  result = [NSMutableString stringWithCapacity: lentext];
  raw = [data bytes];
  ixtext = 0; 

  while (true) {
    ctremaining = lentext - ixtext;
    if (ctremaining <= 0) 
       break;        
    for (i = 0; i < 3; i++) { 
       unsigned long ix = ixtext + i;
       if (ix < lentext)
          input[i] = raw[ix];
       else
  input[i] = 0;
  }
  output[0] = (input[0] & 0xFC) >> 2;
  output[1] = ((input[0] & 0x03) << 4) | ((input[1] & 0xF0) >> 4);
  output[2] = ((input[1] & 0x0F) << 2) | ((input[2] & 0xC0) >> 6);
  output[3] = input[2] & 0x3F;
  ctcopy = 4;
  switch (ctremaining) {
    case 1: 
      ctcopy = 2; 
      break;
    case 2: 
      ctcopy = 3; 
      break;
  }

  for (i = 0; i < ctcopy; i++)
     [result appendString: [NSString stringWithFormat: @"%c", base64EncodingTable[output[i]]]];

  for (i = ctcopy; i < 4; i++)
     [result appendString: @"="];

  ixtext += 3;
  charsonline += 4;

  if ((length > 0) && (charsonline >= length))
    charsonline = 0;
  }     
  return result;
}

@end

对于Base64解码:

#import <Foundation/Foundation.h>

@class NSString;

@interface NSData (NSDataAdditions)

+ (NSData *) base64DataFromString:(NSString *)string;

@end

-------------------------------------------

#import "NSDataAdditions.h"

@implementation NSData (NSDataAdditions)

+ (NSData *)base64DataFromString: (NSString *)string
{
    unsigned long ixtext, lentext;
    unsigned char ch, inbuf[4], outbuf[3];
    short i, ixinbuf;
    Boolean flignore, flendtext = false;
    const unsigned char *tempcstring;
    NSMutableData *theData;

    if (string == nil)
    {
        return [NSData data];
    }

    ixtext = 0;

    tempcstring = (const unsigned char *)[string UTF8String];

    lentext = [string length];

    theData = [NSMutableData dataWithCapacity: lentext];

    ixinbuf = 0;

    while (true)
    {
        if (ixtext >= lentext)
        {
            break;
        }

        ch = tempcstring [ixtext++];

        flignore = false;

        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 = true;
        }
        else if (ch == '/')
        {
            ch = 63;
        }
        else
        {
            flignore = true; 
        }

        if (!flignore)
        {
            short ctcharsinbuf = 3;
            Boolean flbreak = false;

            if (flendtext)
            {
                if (ixinbuf == 0)
                {
                    break;
                }

                if ((ixinbuf == 1) || (ixinbuf == 2))
                {
                    ctcharsinbuf = 1;
                }
                else
                {
                    ctcharsinbuf = 2;
                }

                ixinbuf = 3;

                flbreak = true;
            }

            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++)
                {
                    [theData appendBytes: &outbuf[i] length: 1];
                }
            }

            if (flbreak)
            {
                break;
            }
        }
    }

    return theData;
}

    @end

在mvds的出色改进中，存在两个问题。更改代码如下:

raw = tmpbuf;
inp = 0;
outbuf[outp++] = base64EncodingTable[(raw[inp] & 0xFC) >> 2];
outbuf[outp++] = base64EncodingTable[((raw[inp] & 0x03) << 4) | ((raw[inp+1] & 0xF0) >> 4)];
if ( left == 2 ) outbuf[outp++] = base64EncodingTable[((raw[inp+1] & 0x0F) << 2) | ((raw[inp+2] & 0xC0) >> 6)];
else outbuf[outp++] = '=';
outbuf[outp++] = '=';