我该如何在iOS上进行base64编码？

#import "NSDataAdditions.h"
@implementation NSData (NSDataAdditions)

+ (NSData *) base64DataFromString: (NSString *)string {
  unsigned long ixtext, lentext;
  unsigned char ch, input[4], output[3];
  short i, ixinput;
  Boolean flignore, flendtext = false;
  const char *temporary;
  NSMutableData *result;

  if (!string)
    return [NSData data];

  ixtext = 0;
  temporary = [string UTF8String];
  lentext = [string length];
  result = [NSMutableData dataWithCapacity: lentext];
  ixinput = 0;

  while (true) {
    if (ixtext >= lentext)
      break;
    ch = temporary[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 ctcharsinput = 3;
      Boolean flbreak = false;

      if (flendtext) {
         if (ixinput == 0)
           break;              
         if ((ixinput == 1) || (ixinput == 2))
           ctcharsinput = 1;
         else
           ctcharsinput = 2;
         ixinput = 3;
         flbreak = true;
      }

      input[ixinput++] = ch;

      if (ixinput == 4){
        ixinput = 0;
        output[0] = (input[0] << 2) | ((input[1] & 0x30) >> 4);
        output[1] = ((input[1] & 0x0F) << 4) | ((input[2] & 0x3C) >> 2);
        output[2] = ((input[2] & 0x03) << 6) | (input[3] & 0x3F);
        for (i = 0; i < ctcharsinput; i++)
        [result appendBytes: &output[i] length: 1];
      }
    if (flbreak)
      break;
    }
  }
  return result;
}
@end

@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”的范围并在返回之前将“dest”附加上（2-byt）“=”字符来添加填充。

然后可以向NSString添加一个类别，如下所示：

@implementation NSString (StringUtils)

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

 return [theData newStringInBase64FromData];
}

@end

iOS 7中

        NSData *data=[[NSData alloc]init];
        [data base64Encoding];

以下是将NSData对象转换为Base 64的示例。它还展示了如何反向操作（解码Base 64编码的NSData对象）：

NSData *dataTake2 = 
  [@"iOS Developer Tips" dataUsingEncoding:NSUTF8StringEncoding];

// Convert to Base64 data
NSData *base64Data = [dataTake2 base64EncodedDataWithOptions:0];

// Do something with the data...

// Now convert back from Base64
NSData *nsdataDecoded = [base64Data initWithBase64EncodedData:base64Data options:0];

iOS从iOS 4版本开始就内置了Base64编码和解码方法（不使用libresolv）。然而，它直到iOS 7 SDK才被声明。苹果文档说明，当针对iOS 4及以上版本时，您可以使用它。

NSData *myData = ... some data
NSString *base64String = [myData base64Encoding];
NSData *decodedData = [[NSData alloc] initWithBase64Encoding:base64String];

@implementation Base64Converter
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', '+', '/'
};
+ (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

在调用call时

 [Base64Converter base64StringFromData:dataval length:lengthval];

就是这样...

 + (NSString *)toBase64String:(NSString *)string {
    NSData *data = [string dataUsingEncoding: NSUnicodeStringEncoding];

    NSString *ret = [data base64EncodedStringWithOptions:NSDataBase64Encoding64CharacterLineLength];

    return ret;
    }

    + (NSString *)fromBase64String:(NSString *)string {
NSData *aData = [string dataUsingEncoding:NSUTF8StringEncoding];
NSData *aDataDecoded = [[NSData alloc]initWithBase64EncodedString:string options:0];
NSString *decryptedStr = [[NSString alloc]initWithData:aDataDecoded encoding:NSUTF8StringEncoding];

return [decryptedStr autorelease];

}

• 我还添加了相关操作的示例方法。

  //
  //  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:- 字符串转Base64编码方法
      //----------------------------------------------------------------
  
      func sampleStringEncodingAndDecoding() {
          if let base64String = self.base64Encode(string: "TestString") {
              print("Base64编码后的字符串：\n\(base64String)")
              if let originalString = self.base64Decode(base64String: base64String) {
                  print("Base64解码后的字符串：\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:- 图片转Base64编码方法
      //----------------------------------------------------------------
  
      func sampleImageEncodingAndDecoding() {
          if let base64ImageString = self.base64Encode(image: UIImage.init(named: "yourImageName")!) {
              print("Base64编码后的图片：\n\(base64ImageString)")
              if let originaImage = self.base64Decode(base64ImageString: base64ImageString) {
                  print("原始图像数据：\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
      }
  
  
  }
  

下载 Base64

执行以下代码将图像转换为Base64

NSString *base64String=[UIImagePNGRepresentation(image) base64Encoding];