JSON Parse and stringify are the two function to convert a string into object (by deserialization) and an object into string (by serialization of the object).
Can anyone explain me the exact methodology for the both function? I expect an answer describing the steps in detail.
Note: I am not looking for a difference but the methodology for implementation.
Just the steps in simple English words.
Related
Chrome Developer Console is console.loging this:
Your JSON sent is>> {yourVariable: "nothing yet"}
So i know the value "nothing yet" in the {yourVariable: "nothing yet"} JSON object is a string. But how do I know the type of the key yourVariable?
Is there a way how to find that out using the Chrome console only?
All object keys are strings with quotes or without quotes. Try this way to see it. May be you are confused with console print because console print it without quotes and we usually write with quotes.
var jsonObj = {person:"me","age":"30", 123:"123"};
Object.keys(jsonObj).forEach(function(key){
console.log(typeof key)}
);
I have a slightly different take on this question which does not invalidate the comments or answer that you received, but is worth considering.
Because you are talking about JSON, there is no intrinsic datatype in your example. As stated on the JSON.org page:
JSON (JavaScript Object Notation) is a lightweight data-interchange
format. It is easy for humans to read and write. It is easy for
machines to parse and generate.
The point is, that there is a difference between JSON, which is a representation of javascript objects, arrays etc., and variables of those types in javascript.
If you remind yourself that JSON is a form of serialization it makes a lot more sense. Javascript objects for example, can include functions, but a javascript function is not a portable thing, so in rendering some JSON from a javascript object, it is up to the language creating the JSON to do whatever it it needs to in order to convert the data it needs to represent, and that may include simplification and in many cases removal of elements that are incompatible JSON.
The other thing to keep in mind, is that all modern languages have functions or libraries that can parse JSON and turn them into variables or objects that work in those languages. In doing so, they have arguments that can completely change the way the JSON is converted back into instance variables.
For example, in PHP you can choose to have the JSON create one or more PHP objects, or an array of php variables.
In summary, JSON doesn't have variables with datatypes at all. It is a representation of data, that is portable across languages, but the languages must decode the JSON and create objects or variables that are valid in their own runtime.
I have a fairly large and complex NSManagedObject that I'm manipulating within my application and sending back to a server as JSON. My plan was to do what I need to do in my application, convert the object to a Dictionary, and then send it along after calling NSJSONSerialization.dataWithJSONObject (I've also tried using SwiftyJSON, which I think is doing more or less the same thing). This was all working fine until I needed to include some dates.
Basically all of the documentation I've seen says that serialization works just fine with a certain list of object types, which does not include NSDate. Sadly, I need some dates. I should note that I am working with a dictionary of dictionaries that may have dates scattered all up and down the tree, so if I recursively run through to convert them all to strings I'm going to have to do a whole lot of copying to NSMutable dictionaries. Surely there's an easier way? I'm a bit new to Swift and iOS development and I can't help feeling like I'm either doing something wrong or that there is a built-in solution to this problem that I'm just missing. I can't be the first person who wants to send back a date as JSON. Any help would be much appreciated.
Thanks,
Alex
Apple NSJSONSerialization Class Reference says;
You use the NSJSONSerialization class to convert JSON to Foundation
objects and convert Foundation objects to JSON.
An object that may be converted to JSON must have the following
properties:
The top level object is an NSArray or NSDictionary.
All objects are instances of NSString, NSNumber, NSArray,
NSDictionary, or NSNull.
All dictionary keys are instances of NSString.
Numbers are not NaN or infinity.
Other rules may apply. Calling isValidJSONObject: or attempting a
conversion are the definitive ways to tell if a given object can be
converted to JSON data.
I think you should convert your dates to String and add them to your Dictionary. But it says; Other rules may apply. Calling isValidJSONObject: Just try to create a dictionary with your NSDate object and call the isValidJSONObject if it returns true it should be work.
I'm really at my wit's end here... I'm using VB-JSON Parser (http://www.ediy.co.nz/vbjson-json-parser-library-in-vb6-xidc55680.html) and I have the following array :
[{"timestamp":1410001952,"tid":2834225,"price":"483.77"}]
The documentation is really minimal and I have no clue whatsoever of how to access the array, been searching for several hours now on how to resolve this.
How can I get the "price" value? I know that i can use .item("price") when there is no array but I don't know what to do when there's an array and there is no name before it.
First have a look at Parsing JSON in Excel VBA
It explains the JScript way of parsing JSON string.
Browsing through the net, I found it really hard to get a complete VBA based JSON parser.
Some options are available in the VB version and then there are few online parsers who promise to parse JSON and convert them in Excel. These ones work fine with simple JSON data structure. But once you feed in a complex data set with nested arrays and structures, they simply fail.
Using JavaScript features of parsing JSON, on top of ScriptControl, we can create a parser in VBA which will list each and every data point inside the JSON. No matter how nested or complex the data structure is, as long as we provide a valid JSON, this parser will return a complete tree structure.
JavaScript’s Eval, getKeys and getProperty methods provide building blocks for validating and reading JSON.
Coupled with a recursive function in VBA we can iterate through all the keys (up to nth level) in a JSON string. Then using a Tree control (used in this article) or a dictionary or even on a simple worksheet, we can arrange the JSON data as required.
Here, you can find a complete VBA example.
There is a JSON serializer in .NET: http://msdn.microsoft.com/en-us/library/system.runtime.serialization.json
I am attempting to consume an API that I do not have control over which is somewhat poorly documentented and somewhat inconsistent. This means that sometimes, the API returns a different type than what is documented or what you would normally see. For this example, we'll look at a case when an array was returned in a place where I would normally see a string. That makes a crappy API, but my real problem is: How can I more easily track those things down? Right now, the errors look something like this:
No usable value for identifier
Do not know how to convert JArray(List(JString(3c8723eceb1a), JString(cba8849e7a2f))) into class java.lang.String
After deciphering the problem (why JValue::toString doesn't emit a JSON string is utterly perplexing to me), I can figure out the API returned an array when I made my case class only able to deal with Strings. Great. My issue is that finding this discrepancy between my object model and the contents of the JSON seems significantly more difficult than it should be.
Currently, this is my workflow for hunting down decoding errors:
Hope bad data has some sort of identifying marker. If this is not true, then it is way more guesswork and you will have to repeat the following steps for each entry that looks like the bad bits.
Go through the troubles of converting the JArray(List(JString(...), ...)) from the error message into valid JSON, hoping that I encode JSON the same way at the API endpoint I got the data from does. If this is not true, then I use a JSON formatter (jq) to format all data consistently.
Locate the place in the source data where the decoding error originates from.
Backtrack through arrays and objects to discover how I need to change my object model to more accurately represent what data is coming back to me from the API.
Some background: I'm coming from C++, where I rolled my own JSON deserialization framework for this purpose. The equivalent error when using the library I built is:
Error decoding value at result.taskInstances[914].subtasks[5].identifier: expected std::string but found array value (["3c8723eceb1a","cba8849e7a2f"]) at 1:4084564
This is my process when using my hand-rolled library:
Look at the expected type (std::string) compared with the data that was actually found (["3c8723eceb1a","cba8849e7a2f"]) and alter my data model for the path for the data in the source (result.taskInstances[914].subtasks[5].identifier)
As you can see, I get to jump immediately to the problem that I actually have.
My question is: Is there a way to more quickly debug inconsistencies between my data model and the results I'm getting back from the API?
I'm using json4s-native_2.10 version 3.2.8.
A simplified example:
{ "property": ["3c8723eceb1a", "cba8849e7a2f"] }
Does not mesh with Scala class:
case class Thing(property: String)
The best solution would be to use Try http://www.scala-lang.org/api/current/#scala.util.Try in Scala, but unfortunately json4s API cannot.
So, I think you should use Scala Option type http://www.scala-lang.org/api/current/#scala.Option .
In Scala, and more generally in functional languages, Options are used to represent an object that can be there or not (like à nil value).
For handle parsing failures, you can use parse(str).toOption, which is a function that return an Option[JValue], and you can doing a pattern matching on the resulting value.
For handling extraction of data extraction into case classes, you can use extractOpt function, to do pattern matching on the value.
You can read this answer : https://stackoverflow.com/a/15944506/2330361
I am getting a .net run-time error when attempting to desrialize a JSON string that contains an anonymous function:
Invalid JSON primitive: function.
JSON string itself looks like this:
{
Action: "fadeIn",
Callback: function(){doSomething();}
}
This makes me wonder if it is allowed to have anonymous functions in JSON strings that are to be serialized in .net. More specfically I can only use the .net frameworks's own JavaScriptSerializer class for deserialization. Can anyone confirm this, or have a solution?
JSON is a data representation protocol, and as such it can only be used to represent data, not behavior (which is what functions are). As your deserializer told you, what you have is not valid JSON (it's a valid JavaScript object, though, which causes some confusion). Check the JSON spec for more details on this format.
So to your question - no, you cannot deserialize JSON containing function, because it's not JSON in the first place.