在Swift中，我创建了以下helper函数:

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)")
    }
}

现在不需要第三方类ios 5引入了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);

这段代码对于获取jsondata非常有用。

在Swift 2.0版本中:

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
}

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)
        }
    }
}

这个非常接近最初的Objective-C打印风格

这将在swift4和swift5中工作。

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)

苹果在iOS 5.0和Mac OS X 10.7中添加了JSON解析器和序列化器。看到NSJSONSerialization。

要从NSDictionary或NSArray中生成JSON字符串，你不再需要导入任何第三方框架。

以下是如何做到这一点:

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];
}