Cocoa：如何将 NSAttributedString 保存为 JSON

Question

我有一个NSAttributedString 对象作为自定义对象的属性。我需要将此自定义对象以 JSON 格式保存到磁盘。稍后我需要通过网络将此 JSON 数据发送到 Java 服务器。
我不能使用NSSAttributedString 对象的-(NSString) string 方法，因为我需要能够从磁盘和服务器上重建属性字符串。

Answer 1

NSAttributedString 有两个属性：

• 字符串
• 属性“运行”数组

每个“运行”都有：

• 它适用的整数范围
• 键/值属性字典

使用 enumerateAttributesInRange:options:usingBlock: 将其表示为 JSON 非常容易。

类似：

{
  "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
        }
      }
    }
  ]
}

编辑：这是一个示例实现：

// 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);

Answer 2

您可以尝试从 RTFFromRange 开始：

来自文档：有关支持 RTF 的 OS X 方法的信息，...，请参阅 NSAttributedString Application Kit Additions Reference。

RTF 应该是自包含的。 RTFFromRange：返回 NSData；我认为它可能是某种编码中的字符数据，因此应该很容易转换为 NSString。

（抱歉，刚刚看到该方法仅适用于 MacOS X）。

Answer 3

您可以使用这个简单的代码 sn-p 将 NSAttributedString 转换为 XML，而无需实际解析 NSAttributedString。如果您能负担得起冗长的文本输出，这可以成为 JSON 的人类可读替代方案。

也可用于解码回NSAttributedString。

    let data = NSMutableData()

    let archiver = NSKeyedArchiver(forWritingWithMutableData: data)
    archiver.outputFormat = .XMLFormat_v1_0
    textView.attributedText.encodeWithCoder(archiver)
    archiver.finishEncoding()

    let textAsString = NSString(data: data, encoding: NSUTF8StringEncoding)'

Answer 4

Swift 5 版本的@AbhiBeckert 的answer：

let attributedString: NSAttributedString! // Input -> NSAttributedString
let RUN_ATTRIBUTES_ARRAY: NSMutableArray = []

attributedString!.enumerateAttributes(in: .init(location: 0, length: attributedString!.length), options: [], using: { attributedDictionary, range, stop in // Retrieve all of attributed string's attributes
    let runAttributes: NSMutableDictionary = NSMutableDictionary()
    
    // Convert each attribute's value to a JSON formattable type
    for attribute in attributedDictionary {
        if (attribute.key == .font) {
            let values: NSDictionary = [
                "name": (attribute.value as! NSFont).displayName!,
                "size": (attribute.value as! NSFont).pointSize
            ]
            
            runAttributes.setValue(values, forKey: "font") // Apply the value with its key to a mutable dictionary
        }
    }
    
    // Add the previously accumulated values to a mutable array along with the corresponding range
    RUN_ATTRIBUTES_ARRAY.add([
        "range": [range.lowerBound, range.upperBound],
        "attributes": runAttributes
    ])
})

// Create a dictionary with the attributes and the text value
let dictionary: NSDictionary = [
    "string": attributedString!.string,
    "runs": RUN_ATTRIBUTES_ARRAY
]

// Convert the dictionary to JSON
try {
    let jsonData: Data = try JSONSerialization.data(withJSONObject: dictionary, options: [.prettyPrinted, .sortedKeys])
    print(jsonData) // Output -> JSON
} catch {
    print("Error converting dictionary to JSON")
}

以下代码将 JSON 转换回属性字符串：

private func convertAttributesFromJSONToDictionary(_ attributes: Any) -> [NSAttributedString.Key: Any]? {
    if let attrValue: [String: [String: Any]] = (attributes as? [String: [String: Any]]) {
        /*
         attrValue = [
             "font" : {
               "name" : "Helvetica",
               "size" : 12
             },
             "color" : [255,0,0]
         ]
         */
        var attrDict: [NSAttributedString.Key: Any] = [:]
        
        for (key, value) in attrValue { // Loop through each attribute
            if (key == "font") {
                // Retrieve all attribute values
                var name: String = "Helvetica"
                var size: CGFloat = 12
                
                for (fontKey, fontValue) in value {
                    if (fontKey == "name") {
                        name = (fontValue as! String)
                    } else if (fontKey == "size") {
                        size = (fontValue as! CGFloat)
                    }
                }
                
                if let font: NSFont = NSFont(name: name, size: size) {
                    // Add retrieved values to a dictionary
                    attrDict.updateValue(font, forKey: .font)
                } else {
                    print("Unable to implement font attribute")
                }
            }
        }
        
        return attrDict // Return filled dictionary
    }
    
    return nil
}

public func convertJSONToAttributedString() {
    var dictionary: [String: Any]! // Input -> JSON
    
    // Create attributed string with text string
    guard let string: String = (dictionary["string"] as? String) else {
        print("Incorrect json structure {string}")
    }
    
    let attrString: NSMutableAttributedString = NSMutableAttributedString(string: string)
    
    if let runsDict: [[String: Any]] = (dictionary["runs"] as? [[String: Any]]) { // Check for 'runs' key in JSON data
        /*
         runsDict = [
             {
               "attributes" : {Any},
               "range" : [Int]
             }, {
               "attributes" : {Any},
               "range" : [Int]
             }
         ]
         */
        for run in runsDict { // Loop through each attributes and range section
            var attributes: [NSAttributedString.Key: Any] = [:]
            var range: NSRange?
            
            for (key, value) in run {
                // Retrieve all attributes and the range
                if (key == "attributes") {
                    if let attrDict: [NSAttributedString.Key: Any] = convertAttributesFromJSONToDictionary(value) {
                        attributes = attrDict
                    }
                } else if (key == "range") {
                    if let rangeValue: [Int] = (value as? [Int]) {
                        range = NSRange(location: rangeValue[0], length: (rangeValue[1] - rangeValue[0]))
                    }
                }
                
                // Add retrieved attributes and range to the attributed string
                if ((key == "attributes" || key == "range") && range != nil) {
                    attrString.addAttributes(attributes, range: range!)
                }
            }
        }
    } else {
        print("Incorrect json structure {runs}")
    }

    print(attrString) // Output -> NSAttributedString
}