I'm trying to pass a list of integers (of the form [1,5]) as params in transitionTo in Ember 3.14. I've verified that the list can be read within this function:
afterModel() {
this.transitionTo('newRoute', this.modelFor('lastLevel').list);
},
But I always get this error:
Cannot read property '0' of undefined TypeError: Cannot read property '0' of undefined
How should I transform the list so it will pass into transitionTo()?
I found the pretty simple solution. I had to join the list into a string:
this.transitionTo('newRoute', this.modelFor('lastLevel').list.join(',');
the code in Script (FB setup is already done)
var base = FirebaseApp.getDatabaseByUrl(firebaseUrl,secret);
var data = base.getData();
var rowNum = 1;
var range = Sheet.getRange("A"+rowNum+":DH"+rowNum+"");
for (i in data) {
Logger.log(data[i]);
range.setValues(JSON.parse(data[i]))
rowNum += 1;
range = Sheet.getRange("A"+rowNum+":DH"+rowNum+"");
}
the Logger shows the the 112 elements from Firebase just fine, but I can't get the data parsed correctly. the JSON.parse fails saying "Cannot find method setValues(object)".
The message "Cannot find method setValues(object)" is related to range.setValues() method. It means that JSON.parse() works as expected and returns JSON object, but setValues() argument must be 2D array, not JSON object.
You should convert JSON object to array before using as argument. See an example. In general case, the convertion code depends on the object structure, so we can not write the exact code here. It may appear rather long for 112 elements... But we can append it here after you give more details.
This question is multipart-
(1a) JSON is fundamental to JavaScript, so why is there no JSON type? A JSON type would be a string that is formatted as JSON. It would be marked as parsed/stringified until the data was altered. As soon as the data was altered it would not be marked as JSON and would need to be re-parsed/re-stringified.
(1b) In some software systems, isn't it possible to (accidentally) attempt to send a plain JS object over the network instead of a serialized JS object? Why not make an attempt to avoid that?
(1c) Why can't we call JSON.parse on a straight up JavaScript object without stringifying it first?
var json = { //JS object in properJSON format
"baz":{
"1":1,
"2":true,
"3":{}
}
};
var json0 = JSON.parse(json); //will throw a parse error...bad...it should not throw an error if json var is actually proper JSON.
So we have no choice but to do this:
var json0= JSON.parse(JSON.stringify(json));
However, there are some inconsistencies, for example:
JSON.parse(true); //works
JSON.parse(null); //works
JSON.parse({}); //throws error
(2) If we keep calling JSON.parse on the same object, eventually it will throw an error. For example:
var json = { //same object as above
"baz":{
"1":1,
"2":true,
"3":{}
}
};
var json1 = JSON.parse(JSON.stringify(json));
var json2 = JSON.parse(json1); //throws an error...why
(3) Why does JSON.stringify infinitely add more and more slashes to the input? It is not only hard to read the result for debugging, but it actually puts you in dangerous state because one JSON.parse call won't give you back a plain JS object, you have to call JSON.parse several times to get back the plain JS object. This is bad and means it is quite dangerous to call JSON.stringify more than once on a given JS object.
var json = {
"baz":{
"1":1,
"2":true,
"3":{}
}
};
var json2 = JSON.stringify(json);
console.log(json2);
var json3 = JSON.stringify(json2);
console.log(json3);
var json4 = JSON.stringify(json3);
console.log(json4);
var json5 = JSON.stringify(json4);
console.log(json5);
(4) What is the name for a function that we should be able to call over and over without changing the result (IMO how JSON.parse and JSON.stringify should behave)? The best term for this seems to be "idempotent" as you can see in the comments.
(5) Considering JSON is a serialization format that can be used for networked objects, it seems totally insane that you can't call JSON.parse or JSON.stringify twice or even once in some cases without incurring some problems. Why is this the case?
If you are someone who is inventing the next serialization format for Java, JavaScript or whatever language, please consider this problem.
IMO there should be two states for a given object. A serialized state and a deserialized state. In software languages with stronger type systems, this isn't usually a problem. But with JSON in JavaScript, if call JSON.parse twice on the same object, we run into fatal exceptions. Likewise, if we call JSON.stringify twice on the same object, we can get into an unrecoverable state. Like I said there should be two states and two states only, plain JS object and serialized JS object.
1) JSON.parse expects a string, you are feeding it a Javascript object.
2) Similar issue to the first one. You feed a string to a function that needs an object.
3) Stringfy actually expects a string, but you are feeding it a String object. Therefore, it applies the same measures to escape the quotes and slashes as it would for the first string. So that the language can understand the quotes, other special characters inside the string.
4) You can write your own function for this.
5) Because you are trying to do a conversion that is illegal. This is related to the first and second question. As long as the correct object types are fed, you can call it as many times as you want. The only problem is the extra slashes but it is in fact the standard.
We'll start with this nightmare of your creation: string input and integer output.
IJSON.parse(IJSON.stringify("5")); //=> 5
The built-in JSON functions would not fail us this way: string input and string output.
JSON.parse(JSON.stringify("5")); //=> "5"
JSON must preserve your original data types
Think of JSON.stringify as a function that wraps your data up in a box, and JSON.parse as the function that takes it out of a box.
Consider the following:
var a = JSON.stringify;
var b = JSON.parse;
var data = "whatever";
b(a(data)) === data; // true
b(b(a(a(data)))) === data; // true
b(b(b(a(a(a(data)))))) === data; // true
That is, if we put the data in 3 boxes, we have to take it out of 3 boxes. Right?
If I put my data in 2 boxes and take it out of 1, I'm not holding my data yet, I'm holding a box that contains my data. Right?
b(a(a(data))) === data; // false
Seems sane to me...
JSON.parse unboxes your data. If it is not boxed, it cannot unbox it. JSON.parse expects a string input and you're giving it a JavaScript object literal
The first valid call to JSON.parse would return an object. Calling JSON.parse again on this object output would result in the same failure as #1
repeated calls to JSON.stringify will "box" our data multiple times. So of course you have to use repeated calls to JSON.parse then to get your data out of each "box"
Idempotence
No, this is perfectly sane. You can't triple-stamp a double-stamp.
You'd never make a mistake like this, would you?
var json = IJSON.stringify("hi");
IJSON.parse(json);
//=> "hi"
OK, that's idempotent, but what about
var json = IJSON.stringify("5");
IJSON.parse(json);
//=> 5
UH OH! We gave it a string each time, but the second example returns an integer. The input data type has been lost!
Would the JSON functions have failed us here?
var json = JSON.stringify("hi");
JSON.parse(json);
//=> "hi"
All good. And what about the "5" ?
var json = JSON.stringify("5");
JSON.parse(json));
//=> "5"
Yay, the types have been preseved! JSON works, IJSON does not.
Maybe a more real-life example:
OK, so you have a busy app with a lot of developers working on it. It makes
reckless assumptions about the types of your underlying data. Let's say it's a chat app that makes several transformations on messages as they move from point to point.
Along the way you'll have:
IJSON.stringify
data moves across a network
IJSON.parse
Another IJSON.parse because who cares? It's idempotent, right?
String.prototype.toUpperCase — because this is a formatting choice
Let's see the messages
bob: 'hi'
// 1) '"hi"', 2) <network>, 3) "hi", 4) "hi", 5) "HI"
Bob's message looks fine. Let's see Alice's.
alice: '5'
// 1) '5'
// 2) <network>
// 3) 5
// 4) 5
// 5) Uncaught TypeError: message.toUpperCase is not a function
Oh no! The server just crashed. You'll notice it's not even the repeated calling of IJSON.parse that failed here. It would've failed even if you called it once.
Seems like you were doomed from the start... Damned reckless devs and their careless data handling!
It would fail if Alice used any input that happened to also be valid JSON
alice: '{"lol":"pwnd"}'
// 1) '{"lol":"pwnd"}'
// 2) <network>
// 3) {lol:"pwnd"}
// 4) {lol:"pwnd"}
// 5) Uncaught TypeError: message.toUpperCase is not a function
OK, unfair example maybe, right? You're thinking, "I'm not that reckless, I
wouldn't call IJSON.stringify or IJSON.parse on user input like that!"
It doesn't matter. You've fundamentally broken JSON because the original
types can no longer be extracted.
If I box up a string using IJSON, and then unbox it, who knows what I will get back? Certainly not you, and certainly not the developer using your reckless function.
"Will I get a string type back?"
"Will I get an integer?"
"Maybe I'll get an object?"
"Maybe I will get cake. I hope it's cake"
It's impossible to tell!
You're in a whole new world of pain because you've been careless with your data types from the start. Your types are important so start handling them with care.
JSON.stringify expects an object type and JSON.parse expects a string type.
Now do you see the light?
I'll try to give you one reason why JSON.parse cannot be called multiple time on the same data without us having a problem.
you might not know it but a JSON document does not have to be an object.
this is a valid JSON document:
"some text"
lets store the representation of this document inside a javascript variable:
var JSONDocumentAsString = '"some text"';
and work on it:
var JSONdocument = JSON.parse(JSONDocumentAsString);
JSONdocument === 'some text';
this will cause an error because this string is not the representation of a JSON document
JSON.parse(JSONdocument);
// SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data
in this case how could have JSON.parse guessed that JSONdocument (being a string) was a JSON document and that it should have returned it untouched ?
I have the following NancyFX unit test. I use the Shouldly assertion library to give the set of extensions methods that start .Should---
[Fact]
public void Assessment__Should_return_assessment_state_for_specified_user()
{
const AssessmentState assessmentState = AssessmentState.Passed;
var user = Fake.Mentor();
using (var db = Fake.Db())
{
db.Save(user);
Fake.Assessment(user.Id, db, assessmentState);
db.ClearStaleIndexes();
}
var response = Fake.Browser(user.UserName, user.Password)
.Get("/assessment/state/" + user.Id, with => with.HttpRequest());
//var result = (dynamic)body.DeserializeJson<ExpandoObject>();
var result = (dynamic) JsonConvert.DeserializeObject<ExpandoObject>(response.Body.AsString());
result.ShouldNotBe(null);
((AssessmentState) result.State).ShouldBe(assessmentState);
}
This test calls a AssessmentService uri defined as /assessment/state/" + user.Id which returns a simple JSON object definition that has a single property State of type (enum) AssessmentState, either Passed, Failed or NotStarted.
Here is the service handler so you can see there are no tricks.
Get["/assessment/state/{userid}"] = parameters =>
{
var assessment = AssessmentService.GetByUserId(Db, (string)parameters.userid);
return assessment == null ? HttpStatusCode.NotFound : Response.AsJson(new
{
assessment.State
});
};
And here is an example the JSON this service call returns:
{"State":1}
Everything works fine until I try to Deserialize the JSON returned by the fake Nancy browser. First I tried to use the built in method provided by Nancy's BrowserResponse.Body object:
var result = (dynamic)response.Body.DeserializeJson<ExpandoObject>();
This deserializes to an empty object. Which is no good. However, if we use the Newtonsoft equivalent then everything is fine (almost).
var result = (dynamic) JsonConvert.DeserializeObject<ExpandoObject>(response.Body.AsString());
The JSON deserialization now works and so the following Shouldly assertion passes with flying colours:
((AssessmentState) result.State).ShouldBe(assessmentState);
However, for reasons that I suspect have to do with anonymous types, the following line fails at run-time (it compiles fine).
result.ShouldNotBe(null);
That is quite a lot of information. Let me distil it down to two questions:
Why does Nancy's built in JSON deserializer not work given that the Newtonsoft version does?
How do I work with the dynamic types generated by the JSON de-serialisation so that the Shouldly extension methods do not cause a run-time exception?
Thanks
I can't answer the first question, but WRT Shouldly and dynamic types, Shouldly's ShouldNotBe method is an extension method on object. The DLR doesn't allow you to call extension methods on objects typed as dynamic (hence the runtime binder exception you're seeing)
I'd suggest that if you want to call ShouldNotBe(null) on result, you'd have to cast it to an object first (ie: ((object)result).ShouldNotBe(null))
-x
I'm using the JSON lib net.sf.json(http://json-lib.sourceforge.net/apidocs/net/sf/json/package-summary.html) in my scala code.
Also, I'm using the specs BDD framework (http://code.google.com/p/specs/) for unit testing. In the doBefore block, i have the following code:
doBefore {
iter = serversJSON.iterator()
}
serversJSON is a JSONArray object. Outside the doBefore block, I have declared the variables used as follows
var serversJSON:JSONArray = null
var iter:Iterator[JSONArray] = null
But on compilation I'm getting the following error.
error: type mismatch; found :
java.util.Iterator[?0] where type ?0
required:
java.util.Iterator[net.sf.json.JSONArray]
iter = serversJSON.iterator()
I guess the way i have declared the iter object outside doBefore is incorrect. How to fix this?
Please Help
Thank You.
As indicated here, the JSON library's iterator method returns a raw Iterator, not an Iterator[JSONArray]. You'll want to declare it as follows:
var serversJSON:JSONArray = null
var iter:Iterator[_] = null