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Cocoa: How to save NSAttributedString to JSON

I have a NSAttributedString object as a property of a custom object. I need to save this custom object to the disk in JSON format. Later I need to send this JSON data across the network to a Java Server.
I can't use the -(NSString) string method of the NSSAttributedString object because I need to be able to reconstruct the attributed string off the disk and on the server.

like image 445
Marci-man Avatar asked Mar 24 '14 21:03

Marci-man


2 Answers

You could try starting with RTFFromRange:

From the documentation: For information about the OS X methods supporting RTF, ..., see NSAttributedString Application Kit Additions Reference.

RTF should be self contained. RTFFromRange: returns NSData; I would think its probably character data in some encoding so should be easy to convert to NSString.

(Sorry, just read that method is MacOS X only).

like image 30
gnasher729 Avatar answered Sep 27 '22 18:09

gnasher729


NSAttributedString has two properties:

  • the string
  • an array of attribute "runs"

Each "run" has:

  • an integer range that it applies to
  • a dictionary of key/value attributes

It would be very easy to represent that as JSON, using enumerateAttributesInRange:options:usingBlock:.

Something like:

{
  "string" : "Hello World",
  "runs" : [
    {
      "range" : [0,3],
      "attributes" : {
        "font" : {
          "name" : "Arial",
          "size" : 12
        }
      }
    },
    {
      "range" : [3,6],
      "attributes" : {
        "font" : {
          "name" : "Arial",
          "size" : 12
        },
        "color" : [255,0,0]
      }
    },
    {
      "range" : [9,2],
      "attributes" : {
        "font" : {
          "name" : "Arial",
          "size" : 12
        }
      }
    }
  ]
}

EDIT: here's an example implementation:

// create a basic attributed string
NSMutableAttributedString *attStr = [[NSMutableAttributedString alloc] initWithString:@"Hello World" attributes:@{NSFontAttributeName: [NSFont fontWithName:@"Arial" size:12]}];
[attStr addAttribute:NSForegroundColorAttributeName value:[NSColor redColor] range:NSMakeRange(3, 6)];

// build array of attribute runs
NSMutableArray *attributeRuns = [NSMutableArray array];
[attStr enumerateAttributesInRange:NSMakeRange(0, attStr.length) options:0 usingBlock:^(NSDictionary *attrs, NSRange range, BOOL *stop) {
  NSArray *rangeArray = @[[NSNumber numberWithUnsignedInteger:range.location],
                          [NSNumber numberWithUnsignedInteger:range.length]];

  NSMutableDictionary *runAttributes = [NSMutableDictionary dictionary];
  [attrs enumerateKeysAndObjectsUsingBlock:^(id attributeName, id attributeValue, BOOL *stop) {

    if ([attributeName isEqual:NSFontAttributeName]) { // convert font values into a dictionary with the name and size
      attributeName = @"font";
      attributeValue = @{@"name": [(NSFont *)attributeValue displayName],
                         @"size": [NSNumber numberWithFloat:[(NSFont *)attributeValue pointSize]]};

    } else if ([attributeName isEqualToString:NSForegroundColorAttributeName]) { // convert foreground colour values into an array with red/green/blue as a number from 0 to 255
      attributeName = @"color";
      attributeValue = @[[NSNumber numberWithInteger:([(NSColor *)attributeValue redComponent] * 255)],
                         [NSNumber numberWithInteger:([(NSColor *)attributeValue greenComponent] * 255)],
                         [NSNumber numberWithInteger:([(NSColor *)attributeValue blueComponent] * 255)]];

    } else { // skip unknown attributes
      NSLog(@"skipping unknown attribute %@", attributeName);
      return;
    }


    [runAttributes setObject:attributeValue forKey:attributeName];
  }];

  // save the attributes (if there are any)
  if (runAttributes.count == 0)
    return;

  [attributeRuns addObject:@{@"range": rangeArray,
                             @"attributes": runAttributes}];
}];

// build JSON output
NSDictionary *jsonOutput = @{@"string": attStr.string,
                             @"runs": attributeRuns};
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:jsonOutput options:NSJSONWritingPrettyPrinted error:NULL];

NSLog(@"%@", [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding]);
exit(0);
like image 59
Abhi Beckert Avatar answered Sep 27 '22 19:09

Abhi Beckert