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YAJL Framework

The YAJL framework is an Objective-C framework for the YAJL SAX-style JSON parser.


  • Stream parsing, comments in JSON, better error messages.
  • Parse directly from NSString or NSData.
  • Generate JSON from default or custom types.
  • Properly handles large numeric types.
  • Document style parser.
  • Error by exception or out error.


pod "YAJLO"


#import <YAJLO/NSObject+YAJL.h>
#import <YAJLO/YAJLDocument.h>
#import <YAJLO/YAJLGen.h>
#import <YAJLO/YAJLParser.h>

To parse JSON from NSData

NSData *JSONData = [NSData dataWithContentsOfFile:@"example.json"];
NSArray *arrayFromData = [JSONData yajl_JSON];

To parse JSON from NSString

NSString *JSONString = @"[1, 2, 3]";
NSArray *arrayFromString = [JSONString yajl_JSON];

To parse JSON from NSString with error and comments

// With options and out error
NSString *JSONString = @"[1, 2, 3] // Allow comments";
NSError *error = nil;
NSArray *arrayFromString = [JSONString yajl_JSONWithOptions:YAJLParserOptionsAllowComments error:&error];

To generate JSON from an object, NSArray, NSDictionary, etc.

NSDictionary *dict = [NSDictionary dictionaryWithObject:@"value" forKey:@"key"];
NSString *JSONString = [dict yajl_JSONString];
// ==> {"key":"value"}

To generate JSON from an object, beautified with custom indent

// Beautified with custon indent string
NSArray *array = [NSArray arrayWithObjects:@"value1", @"value2", nil];
NSString *JSONString = [dict yajl_JSONStringWithOptions:YAJLGenOptionsBeautify indentString:@"    "];

To use the streaming (or SAX style) parser, use YAJLParser

NSData *data = [NSData dataWithContentsOfFile:@"example.json"];

YAJLParser *parser = [[YAJLParser alloc] initWithParserOptions:YAJLParserOptionsAllowComments];
parser.delegate = self;
[parser parse:data];
if (parser.parserError) {
  NSLog(@"Error:\n%@", parser.parserError);
parser.delegate = nil;

// Include delegate methods from YAJLParserDelegate
- (void)parserDidStartDictionary:(YAJLParser *)parser { }
- (void)parserDidEndDictionary:(YAJLParser *)parser { }

- (void)parserDidStartArray:(YAJLParser *)parser { }
- (void)parserDidEndArray:(YAJLParser *)parser { }

- (void)parser:(YAJLParser *)parser didMapKey:(NSString *)key { }
- (void)parser:(YAJLParser *)parser didAdd:(id)value { }

Parser Options

There are options when parsing that can be specified with initWithParserOptions: (YAJLParser).

  • YAJLParserOptionsAllowComments: Allows comments in JSON
  • YAJLParserOptionsCheckUTF8: Will verify UTF-8
  • YAJLParserOptionsStrictPrecision: Will force strict precision and return integer overflow error, if number is greater than long long.

Parsing as data becomes available

 YAJLParser *parser = [[YAJLParser alloc] init];
 parser.delegate = self;

 // A chunk of data comes...
 YAJLParserStatus status = [parser parse:chunk1];
 // 'status' should be YAJLParserStatusInsufficientData, if its not finished
 if (parser.parserError)
   NSLog(@"Error:\n%@", parser.parserError);

 // Another chunk of data comes...
 YAJLParserStatus status = [parser parse:chunk2];
 // 'status' should be YAJLParserStatusOK if its finished
 if (parser.parserError)
   NSLog(@"Error:\n%@", parser.parserError);

Document style parsing

To use the document style, use YAJLDocument. Usage should be very similar to NSXMLDocument.

 NSData *data = [NSData dataWithContentsOfFile:@"example.json"];
 NSError *error = nil;
 YAJLDocument *document = [[YAJLDocument alloc] initWithData:data parserOptions:YAJLParserOptionsNone error:&error];
 // Access root element at document.root
 NSLog(@"Root: %@", document.root);

Document style parsing as data becomes available

 YAJLDocument *document = [[YAJLDocument alloc] init];
 document.delegate = self;

 NSError *error = nil;
 [document parse:chunk1 error:error];
 [document parse:chunk2 error:error];

 // You can access root element at document.root
 NSLog(@"Root: %@", document.root);

 // Or via the YAJLDocumentDelegate delegate methods

 - (void)document:(YAJLDocument *)document didAddDictionary:(NSDictionary *)dict { }
 - (void)document:(YAJLDocument *)document didAddArray:(NSArray *)array { }
 - (void)document:(YAJLDocument *)document didAddObject:(id)object toArray:(NSArray *)array { }
 - (void)document:(YAJLDocument *)document didSetObject:(id)object forKey:(id)key inDictionary:(NSDictionary *)dict { }

Load JSON from Bundle

id JSONValue = [[NSBundle mainBundle] yajl_JSONFromResource:@"kegs.json"];

Customized Encoding

To implement JSON encodable value for custom objects or override for existing objects, implement - (id)JSON;

For example:

@interface CustomObject : NSObject

@implementation CustomObject

- (id)JSON {
 return [NSArray arrayWithObject:[NSNumber numberWithInteger:1]];



Objective-C bindings for YAJL (Yet Another JSON Library) C library




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