Is there a better way to "Pretty Print" the json string than I'm using

Question

I have json data comes server side.

In case I use the next code I get not pretty printed one line string:

print(String(bytes: jsonData, encoding: String.Encoding.utf8))

To make it pretty printed I use the next code:

if let json = try? JSONSerialization.jsonObject(with: jsonData, options: .mutableContainers) {
   if let prettyPrintedData = try? JSONSerialization.data(withJSONObject: json, options: .prettyPrinted) {
      print(String(bytes: prettyPrintedData, encoding: String.Encoding.utf8) ?? "NIL")
   }
}

But seems that it isn't the best way.

So does anybody know how to pretty print incoming jsonData to print it?

Answer 1

A slightly prettier version of what you have:

if let json = try? JSONSerialization.jsonObject(with: data, options: .mutableContainers),
   let jsonData = try? JSONSerialization.data(withJSONObject: json, options: .prettyPrinted) {
    print(String(decoding: jsonData, as: UTF8.self))
} else {
    print("json data malformed")
}

Answer 2

Basically in Swift exists 2 types for strings: String and NSString

The second one is older (used even in Objective-C) and nowadays more often is used newer String type. However, NSString allows you to pretty print existing strings, which means that f.ex. backslashes will be deleted automatically.

Json received as Data from server

For this case I use such helper:

extension Data {
    var prettyString: NSString? {
        return NSString(data: self, encoding: String.Encoding.utf8.rawValue) ?? nil
    }
}

It's very important to use NSString over String type.

Alternatively you can operate on String, but in the end cast it to AnyObject, like below:

String(data: stringData, encoding: .utf8)! as AnyObject

The result in console looks like this (example of server response):

{
  "message" : "User could not log in",
  "errorCode" : "USER_COULD_NOT_LOG_IN",
  "parameters" : null
}

Pretty string for existing string

To prettify any string you can use second method from above, so cast String to AnyObject. It will also make string looking better. F.ex.:

let myStr: String = ...
print(myStr as AnyObject)

Answer 3

Use the output formatting option on the encoder directly:

let encoder = JSONEncoder()
encoder.outputFormatting = .prettyPrinted

Answer 4

Swift 5 and above

handy extension on Data to pretty-print JSON

extension Data {
    
    func printJson() {
        do {
            let json = try JSONSerialization.jsonObject(with: self, options: [])
            let data = try JSONSerialization.data(withJSONObject: json, options: .prettyPrinted)
            guard let jsonString = String(data: data, encoding: .utf8) else {
                print("Inavlid data")
                return
            }
            print(jsonString)
        } catch {
            print("Error: \(error.localizedDescription)")
        }
    }
}

How to Use:

 let json = """
  {
    "id": 1,
    "name": "Steve Jobs",
    "username": "Steve",
    "email": "jobs@apple.com",
    "address": {
      "street": "Kulas Light",
      "suite": "Apt. 556",
      "city": "San Jose",
      "zipcode": "1234-5678"
    },
    "phone": "1-770-736-8031 x56442"
  }
"""

let jsonData = Data(json.utf8)
// log json data in pretty format
jsonData.printJson()

Answer 5

Data extension:

extension Data {
    
    func printFormatedJSON() {
        if let json = try? JSONSerialization.jsonObject(with: self, options: .mutableContainers),
           let jsonData = try? JSONSerialization.data(withJSONObject: json, options: .prettyPrinted) {
            pringJSONData(jsonData)
        } else {
            assertionFailure("Malformed JSON")
        }
    }
    
    func printJSON() {
        pringJSONData(self)
    }
    
    private func pringJSONData(_ data: Data) {
        print(String(decoding: data, as: UTF8.self))
    }
}

Usage:

data.printFormatedJSON()

Answer 6

here's the answer.

language: Objective-C

---

NSString+PrettyPrint.h

@interface NSString (PrettyPrint)

+ (NSString * _Nonnull)prettifiedJsonStringFromData:(nullable NSData *)data;
+ (NSString * _Nonnull)prettifiedStringFromDictionary:(nullable NSDictionary *)dictionary;

@end

---

NSString+PrettyPrint.m

#import "NSString+PrettyPrint.h"

@implementation NSString (PrettyPrint)

+ (NSString *)prettifiedStringFromDictionary:(nullable NSDictionary *)dictionary {
    
    if (dictionary == nil) { return @"nil"; }
    
    NSMutableString *returnStr = [NSMutableString stringWithString:@"[ \n"];
    
    for (NSString *key in dictionary) {
        [returnStr appendFormat:@"  %@: %@,\n", key, [dictionary valueForKey:key]];
    }

    [returnStr appendFormat:@"]"];

    return returnStr;
}

+ (NSString *)prettifiedJsonStringFromData:(nullable NSData *)data {
    
    if (data == nil) { return @"nil"; }
    
    NSData *jsonData;
    NSError *error = nil;
    
    NSString *jsonStr = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    jsonData = [jsonStr dataUsingEncoding:NSUTF8StringEncoding];
    id jsonObject = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingAllowFragments error:&error];
    if (jsonObject == nil) {
        return @"nil (json object from data)";
    } else {
        BOOL isValidJsonObject = [NSJSONSerialization isValidJSONObject:jsonObject];
        if (isValidJsonObject) {
            NSData *finalData = [NSJSONSerialization dataWithJSONObject:jsonObject options:NSJSONWritingPrettyPrinted error:&error];
            //TODO: error description
            NSString *prettyJson = [[NSString alloc] initWithData:finalData encoding:NSUTF8StringEncoding];
            return prettyJson;
        } else {
            return [NSString stringWithFormat:@"%@\n%@", jsonStr, @" (⚠️ Invalid json object ⚠️)\n"];
        }
    }
}

@end

---

then call methods when u need to use them.

ex1. Print NSData for body, response ...etc

NSLog(@"body: %@", [NSString prettifiedJsonStringFromData:[request HTTPBody]]);

ex2. Print NSDictionary

NSLog(@"headers: %@", [NSString prettifiedStringFromDictionary:[request allHTTPHeaderFields]]);

---

Probably you'll get these results in log.

Answer 7

I can't think of something prettier than a native type.

if let json = try? JSONSerialization.jsonObject(with: jsonData, options: []) {
    if let jsonArray = json as? [Any] { print(jsonArray) }
    else if let jsonDict = json as? [String:Any] { print(jsonDict) }
    else { print("Couldn't convert json") }
}