I had JSON with a date "date_use" :
{"expense":
{"id":1,
"amount":123.3,
"date_use":"2015-07-04T00:00:00Z"}
}
I had an error on date format when I execute this code :
self.realm!.create(Expense.self, value:json["expense"].object, update: true)
Error :
Terminating app due to uncaught exception 'RLMException', reason:
'Invalid value '2015-07-04T00:00:00Z' for property 'date_use'
My question is : What is the good date format for Realm?
The problem here is not the particular date format, but that JSON doesn't support a native date type at all. So you have to serialize dates to a string format. Using RFC 3339, like you have to deal with, is generally a good choice because it avoids ambiguities, so you can stick with that.
Realm's create method doesn't expect deserialized JSON, but a dictionary representation of your object. This expects that you have done already the preprocessing step of transforming date string representations back to Cocoa's native type NSDate. This isn't done automatically because there are date formats, which are ambiguous (unlike yours), which e.g do not provide information about the timezone.
Good news is there are excellent third-party libraries e.g. Realm-JSON, which make it a whole lot easier to deal with that. It brings built-in support for that.
This would also allow to map the property naming scheme returned by your API, e.g. date_use to names which conforms to the more broadly used camel-case dateUse.
If you don't want to introduce another dependency just for that use case, you can use and configure NSDateFormatter to parse dates conforming to your particular subset of the RFC 3339 standard, assuming they always use UTC as timezone, marked through the Z suffix.
// Setup the RFC 3339 date formatter
let rfc3339DateFormatter = NSDateFormatter()
let enUSPOSIXLocale = NSLocale(localeIdentifier: "en_US_POSIX")
rfc3339DateFormatter.locale = enUSPOSIXLocale
rfc3339DateFormatter.dateFormat = "yyyy'-'MM'-'dd'T'HH':'mm':'ss'Z'"
rfc3339DateFormatter.timeZone = NSTimeZone(forSecondsFromGMT: 0)
// Convert the RFC 3339 date time string to an NSDate
var json: AnyObject! = nil
var value = json["expense"] as! [String : AnyObject]
let date: NSDate?
if let dateString = value["date_use"] as? String {
date = rfc3339DateFormatter.dateFromString(dateString)
} else {
date = nil
}
value["date_use"] = date
// Create your object
self.realm!.create(Expense.self, value: value, update: true)
Related
I'm new to Rust.
I try to write a websocket client.
This is my format message:
"[integer, "string", object]"
Is there away to store all value in Vector something like:
let msg: Vec<interface> = vec![123, "event", AnyObject{}];
How to convert it into string and vice versa.
Thanks in advance
Conceptually speaking you want to use an enum. The type of enums used in rust are called tagged unions. Essentially you can think of them as enums which can hold data.
enum Interface {
Int(i32),
String(&'static str),
Object(AnyObject),
// etc
}
// You can then create a vec of different enum variants
let msg: Vec<Interface> = vec![Interface::Int(123), Interface::String("event"), Interface::Object(AnyObject{})];
Assuming you are referring to JSON, then the recommended solution is to use serde with serde_json. serde_json provides a Value enum you can use to represent JSON data in an unknown layout.
// Copied from serde_json docs
enum Value {
Null,
Bool(bool),
Number(Number),
String(String),
Array(Vec<Value>),
Object(Map<String, Value>),
}
However, you don't need to use Value directly (unless you want to) since serde_json provides a macro to make this easier by letting you format your code like JSON.
use serde_json::{json, Value};
let msg: Value = json!([123, "event", {}]);
// You can then serialize a Value into JSON format
println!("{:?}", msg.to_string());
// Output: "[123,\"event\",{}]"
I recommend reading through the overview since they have a bunch of convenient ways for working with JSON.
i have to index documents to elasticsearch to an index which has a date field mapping and i'm trying to build a json with this date value, but ballerina says this seems not possible.
I thought about storing this date value into an xml and after that to convert it to a json but xml has the same problem (i thought this might be a trick...).
I tried to store it into a string and after that to extract the json payload from that string but it gives me this error:
error: {ballerina/io}GenericError message=unrecognized token 'date=time=1591128342000'
I thought about dealing with this string to date conversion from inside elasticsearch but i would like to keep this scenario as the last one. I don't like it, beacause i have to do some queries based on timestamp after and storing date as a string would give me additional problems
So is there any way to trick ballerina in order to achive this json containing a date value ?
-----here is snapshot of the code giving me the error-----
It says:
incompatible types: expected 'json', found 'ballerina/time:Time'
JSON is a text format that is completely language independent (see e.g. json.org).
time:Time is a Ballerina language specific type JSON knows nothing about. Because there is no implicit conversion (for a good reason) one have to provide the conversion.
In this case you most likely want to convert time:Time to a ISO 8601 string presentation with time:toString.
The following code (Ballerina 1.2):
import ballerina/io;
import ballerina/time;
public function main() {
var btime = time:currentTime();
var j = <json> {
time: time:toString(btime)
};
io:println(j.toJsonString());
}
Correctly prints:
{"time":"2020-06-03T08:39:07.897+03:00"}
Maryam Ziyad has written a good introduction to Ballerina's JSON support.
The following code is updated for Ballerina Swan Lake Update 1 (2201.1.0) to show how to convert a Ballerina UTC time (time:Utc) to JSON representation. Note that it's also possible to use localized time (time:Civil) but that is no different from time to JSON conversion point of view.
One can read more about Ballerina time handling from the documentation of time module.
import ballerina/io;
import ballerina/time;
public function main() {
time:Utc now = time:utcNow(3);
json j = {
time: time:utcToString(now)
};
io:println(j.toJsonString());
}
That correctly prints:
{"time":"2022-07-20T06:03:46.078Z"}
I am converting a TFDMemTable to JSON via SaveToStream(). Then I use TJSONObject::ParseJSONValue() to get the JSON object. After some parsing, I return the JSON in string format via ToString().
TStringStream *Stream = new TStringStream();
TJSONObject *Json = new TJSONObject();
fdMemTable->SaveToStream(Stream.get(), sfJSON);
TJSONObject *JsonParsed = (TJSONObject*) Json->ParseJSONValue(Stream->DataString);
...
return JsonParsed->ToString();
All through this, the dates remain in the form 20180329T013152 instead of 2018-03-29T01:31:52. I am looking to see if there is any option that I can set. TJsonOptions seems to be close to what I am looking for, but seems to only be used with ObjectToJsonString().
Does anyone know any such option, or do I have to do this conversion per date/time field?
There is no date/time type in JSON. Date/time values are just arbitrary string values with formatting. So, unless TFDMemTable provides an option to specify date/time formatting for its JSON output, then you will have to handle this on a per-field basis.
BTW, you don't need to create a TJSONObject object to call ParseJSONValue():
TJSONObject *JsonParsed = (TJSONObject*) TJSONObject::ParseJSONValue(Stream->DataString);
I'm trying to understand what is going on when I query data from a database and provide it to JSON and then push it to a GUI, in regards to what and when is converting to a string.
If I make a call to a database and provide this data as JSON to the front end, my JSON may look like
MyData{ [["Name": "Anna", "Age": 50],["Name": "Bob", "Age": 40 ]};
Visually it appears as if the value for Name is a string (as it's in quote marks) and the value for Age is an integer (as of no quote marks).
My 2 questions are
Is my understanding that the value for Name is a string and the value of Age is an integer or does JavaScript convert/cast behind the scenes?
How would I specify the type DateTime. According to The "right" JSON date format I actually just ensure the format is correct but ultimately it's a string.
Is my understanding that the value for Name is a string and the value of Age is an integer...?
Almost. It's a number, which may or may not be an integer. For instance, 10.5 is a number, but not an integer.
...or does JavaScript convert/cast behind the scenes?
JavaScript and JSON are different things. JSON defines that the number will be represented by a specific format of digits, . and possibly the e or E character. Whatever environment you're parsing the JSON in will map that number to an appropriate data type in its environment. In JavaScript's case, it's an IEEE-754 double-precision binary floating point number. So in that sense, JavaScript may cast/convert the number, if the JSON defines a number that can't be accurately represented in IEEE-754, such as 9007199254740999 (which becomes the number 9007199254741000 because IEEE-754 only has ~15 digits of decimal precision).
How would I specify the type DateTime. According to The "right" JSON date format I actually just ensure the format is correct but ultimately it's a string.
JSON has a fixed number of types: object, array, string, number, boolean, null. You can't add your own. So what you do is encode any type meta-data you want into either the key or value, or use an object with separate properties for type and value, and enforce that agreement at both ends.
An example of doing this is the common format for encoding date/time values: "/Date(1465198261547)/". As far as the JSON parser is concerned, that's just a string, but many projects use it as an indicator that it's actually a date, with the number in the parens being the number of milliseconds since The Epoch (Jan 1 1970 at midnight, GMT).
Two concepts related to this are a replacer and a reviver: When converting a native structure to JSON, the JSON serializer you're using may support a replacer which lets you replace a value during the serialization with another value. The JSON parser you're using may support a reviver that lets you handle the process in the other direction.
For example, if you were writing JavaScript code and wanted to preserve Dates across a JSON layer, you might do this when serializing to JSON:
var obj = {
foo: "bar",
answer: 42,
date: new Date()
};
var json = JSON.stringify(obj, function(key, value) {
var rawValue = this[key];
if (rawValue instanceof Date) {
// It's a date, convert it to our special format
return "/Date(" + rawValue.getTime() + ")/";
}
return value;
});
console.log(json);
That uses the "replacer" parameter of JSON.stringify to encode dates in the way I described earlier.
Then you might do this when parsing that JSON:
var json = '{"foo":"bar","answer":42,"date":"/Date(1465199095286)/"}';
var rexIsDate = /^\/Date\((-?\d+)\)\/$/;
var obj = JSON.parse(json, function(key, value) {
var match;
if (typeof value == "string" && (match = rexIsDate.exec(value)) != null) {
// It's a date, create a Date instance using the number
return new Date(+match[1]);
}
return value;
});
console.log(obj);
That uses a "reviver" to detect keys in the special format and convert them back into Date instances.
The specific format of a JSON string can be described by JSON Schema, as described here; in particular, date-time apparently is a type already defined in JSON Schema.
I'm trying to deserialize some JSON coming back from couchbase into a dynamic type.
The document is something like this so creating a POCO for this would be overkill:
{
UsersOnline: 1
}
I figured that something like this would do the trick, but it seems to deserialize into a dynamic object with the value just being the original JSON
var jsonObj = _client.GetJson<dynamic>(storageKey);
results in:
jsonObj { "online": 0 }
Is there anyway I can get the couchbase deserializer to generate the dynamic type for me?
Cheers
The default deserializer for the client uses .NET's binary serializer, so when you save or read a JSON string, it's just a string. GetJson will always just return a string. However, there are a couple of options:
You could convert JSON records to Dictionary instances:
var appJson = "{ \"UsersOnline\" : 1, \"NewestMember\" : \"zblock\" }";
var result = client.ExecuteStore(StoreMode.Set, "userCount", appJson);
var item = client.GetJson<Dictionary<string, object>>("userCount");
Console.WriteLine("There are {0} users online. The newest member is {1}.",
item["UsersOnline"], item["NewestMember"]);
Or you could use a dynamic ExpandoObject instance:
var appJson = "{ \"UsersOnline\" : 1, \"NewestMember\" : \"zblock\" }";
var result = client.ExecuteStore(StoreMode.Set, "userCount", appJson);
dynamic item = client.GetJson<ExpandoObject>("userCount");
Console.WriteLine("There are {0} users online. The newest member is {1}.",
item.UsersOnline, item.NewestMember);
In either case you're losing static type checking, which seems like it's OK for your purposes. In both cases you get access to the JSON properties without having to parse the JSON into a POCO though...
Edit: I wrote a couple of extension methods that may be useful and blogged about them at http://blog.couchbase.com/moving-no-schema-stack-c-and-dynamic-types