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Generate JSON string from NSDictionary in iOS

Sophia Hammond |

I have a dictionary I need to generate a JSON string by using dictionary. Is it possible to convert it? Can you guys please help on this?

2

14 Answers

Apple added a JSON parser and serializer in iOS 5.0 and Mac OS X 10.7. See NSJSONSerialization.

To generate a JSON string from a NSDictionary or NSArray, you do not need to import any third party framework anymore.

Here is how to do it:

NSError *error;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dictionaryOrArrayToOutput options:NSJSONWritingPrettyPrinted // Pass 0 if you don't care about the readability of the generated string error:&error];
if (! jsonData) { NSLog(@"Got an error: %@", error);
} else { NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
}
7

Here are categories for NSArray and NSDictionary to make this super-easy. I've added an option for pretty-print (newlines and tabs to make easier to read).

@interface NSDictionary (BVJSONString)
-(NSString*) bv_jsonStringWithPrettyPrint:(BOOL) prettyPrint;
@end

.

@implementation NSDictionary (BVJSONString) -(NSString*) bv_jsonStringWithPrettyPrint:(BOOL) prettyPrint { NSError *error; NSData *jsonData = [NSJSONSerialization dataWithJSONObject:self options:(NSJSONWritingOptions) (prettyPrint ? NSJSONWritingPrettyPrinted : 0) error:&error]; if (! jsonData) { NSLog(@"%s: error: %@", __func__, error.localizedDescription); return @"{}"; } else { return [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding]; } }
@end

.

@interface NSArray (BVJSONString)
- (NSString *)bv_jsonStringWithPrettyPrint:(BOOL)prettyPrint;
@end

.

@implementation NSArray (BVJSONString)
-(NSString*) bv_jsonStringWithPrettyPrint:(BOOL) prettyPrint { NSError *error; NSData *jsonData = [NSJSONSerialization dataWithJSONObject:self options:(NSJSONWritingOptions) (prettyPrint ? NSJSONWritingPrettyPrinted : 0) error:&error]; if (! jsonData) { NSLog(@"%s: error: %@", __func__, error.localizedDescription); return @"[]"; } else { return [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding]; }
}
@end
4

To convert a NSDictionary to a NSString:

NSError * err;
NSData * jsonData = [NSJSONSerialization dataWithJSONObject:myDictionary options:0 error:&err];
NSString * myString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
0

NOTE: This answer was given before iOS 5 was released.

Get the json-framework and do this:

#import "SBJsonWriter.h"
...
SBJsonWriter *jsonWriter = [[SBJsonWriter alloc] init];
NSString *jsonString = [jsonWriter stringWithObject:myDictionary];
[jsonWriter release];

myDictionary will be your dictionary.

3

You can also do this on-the-fly by entering the following into the debugger

po [[NSString alloc] initWithData:[NSJSONSerialization dataWithJSONObject:yourDictionary options:1 error:nil] encoding:4];
3

You can pass array or dictionary. Here, I am taking NSMutableDictionary.

NSMutableDictionary *contentDictionary = [[NSMutableDictionary alloc]init];
[contentDictionary setValue:@"a" forKey:@"b"];
[contentDictionary setValue:@"c" forKey:@"d"];

To generate a JSON string from a NSDictionary or NSArray, You don't need to import any third party framework. Just use following code:-

NSError *error;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:contentDictionary // Here you can pass array or dictionary options:NSJSONWritingPrettyPrinted // Pass 0 if you don't care about the readability of the generated string error:&error];
NSString *jsonString;
if (jsonData) { jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding]; //This is your JSON String //NSUTF8StringEncoding encodes special characters using an escaping scheme
} else { NSLog(@"Got an error: %@", error); jsonString = @"";
}
NSLog(@"Your JSON String is %@", jsonString);
NSMutableDictionary *contentDictionary = [[NSMutableDictionary alloc]init]; [contentDictionary setValue:@"a" forKey:@"b"]; [contentDictionary setValue:@"c" forKey:@"d"]; NSData *data = [NSJSONSerialization dataWithJSONObject:contentDictionary options:NSJSONWritingPrettyPrinted error:nil]; NSString *jsonStr = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
1

In Swift (version 2.0):

class func jsonStringWithJSONObject(jsonObject: AnyObject) throws -> String? { let data: NSData? = try? NSJSONSerialization.dataWithJSONObject(jsonObject, options: NSJSONWritingOptions.PrettyPrinted) var jsonStr: String? if data != nil { jsonStr = String(data: data!, encoding: NSUTF8StringEncoding) } return jsonStr
}

Now no need third party classes ios 5 introduced Nsjsonserialization 

NSString *urlString=@"Your url";
NSString *urlUTF8 = [urlString stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSURL *url=[[NSURL alloc]initWithString:urlUTF8];
NSURLRequest *request=[NSURLRequest requestWithURL:url];
NSURLResponse *response;
NSData *GETReply = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];
NSError *myError = nil;
NSDictionary *res = [NSJSONSerialization JSONObjectWithData:GETReply options:NSJSONReadingMutableLeaves|| NSJSONReadingMutableContainers error:&myError];
Nslog(@"%@",res);

this code can useful for getting jsondata.

1

Here is the Swift 4 version

extension NSDictionary{
func toString() throws -> String? { do { let data = try JSONSerialization.data(withJSONObject: self, options: .prettyPrinted) return String(data: data, encoding: .utf8) } catch (let error){ throw error }
}

}

Usage Example

do{ let jsonString = try dic.toString() } catch( let error){ print(error.localizedDescription) }

Or if you are sure it is valid dictionary then you can use

let jsonString = try? dic.toString()
2

This will work in swift4 and swift5.

let dataDict = "the dictionary you want to convert in jsonString"
let jsonData = try! JSONSerialization.data(withJSONObject: dataDict, options: JSONSerialization.WritingOptions.prettyPrinted)
let jsonString = NSString(data: jsonData, encoding: String.Encoding.utf8.rawValue)! as String
print(jsonString)

In Swift, I've created the following helper function:

class func nsobjectToJSON(swiftObject: NSObject) { var jsonCreationError: NSError? let jsonData: NSData = NSJSONSerialization.dataWithJSONObject(swiftObject, options: NSJSONWritingOptions.PrettyPrinted, error: &jsonCreationError)! if jsonCreationError != nil { println("Errors: \(jsonCreationError)") } else { // everything is fine and we have our json stored as an NSData object. We can convert into NSString let strJSON : NSString = NSString(data: jsonData, encoding: NSUTF8StringEncoding)! println("\(strJSON)") }
}

As of ISO7 at least you can easily do this with NSJSONSerialization.

1 
public func jsonPrint(_ o: NSObject, spacing: String = "", after: String = "", before: String = "") { let newSpacing = spacing + " " if o.isArray() { print(before + "[") if let a = o as? Array<NSObject> { for object in a { jsonPrint(object, spacing: newSpacing, after: object == a.last! ? "" : ",", before: newSpacing) } } print(spacing + "]" + after) } else { if o.isDictionary() { print(before + "{") if let a = o as? Dictionary<NSObject, NSObject> { for (key, val) in a { jsonPrint(val, spacing: newSpacing, after: ",", before: newSpacing + key.description + " = ") } } print(spacing + "}" + after) } else { print(before + o.description + after) } }
}

This one is pretty close to original Objective-C print style

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