C#•2y ago

❔ Null warning from accessing weather results from an API call

I'm creating a weather app that allows you to type in the name of a city and then get it's information from which you can use a key to get the weather for it. I've gotten the first part down, but I'm having trouble with the second part in that I try to get the JSON results from a different api link where I need the city key. I keep getting a null warning from my code when I try to get and deserialize the json, but I don't see anything in the JSON itself that has a null value. any suggestions? pastebin of code: https://paste.mod.gg/miyqeovcslff/0 pic of json:

BlazeBin - miyqeovcslff

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101 Replies

phaseshift•2y ago

depends how you're deserialzing it

GIGA BRAINOP•2y ago

i'm trying to serialize it into an object

phaseshift•2y ago

show code...

GIGA BRAINOP•2y ago

in the blazebin or i can paste it here 1 sec

phaseshift•2y ago

nah link is good

GIGA BRAINOP•2y ago

phaseshift•2y ago

so what is null? weatherResult?

GIGA BRAINOP•2y ago

yeah, let me run the code again real quick and sc it

daysleeper•2y ago

null warnings usually just say that if you put null into the field it will throw exception so you can put a null reference checker (either ?? or if statement) and it should do assuming that codewise nothing is crashing or not working correctly

phaseshift•2y ago

What is the exact 'null warning' that you get?

GIGA BRAINOP•2y ago

gimme a sec my code that was working all this time isn't working anymore System.Net.Http.HttpRequestException: 'Response status code does not indicate success: 503 (Unauthorized).' i'm now getting this when i run my program at this line of code // Get JSON results and deserialize var citySearch = await client.GetFromJsonAsync<List<Root>>(link);

daysleeper•2y ago

authorize

phaseshift•2y ago

maybe your apikey is rate limited

GIGA BRAINOP•2y ago

aw man no way i forgot about that so it says 50 calls a day so if i've run my program 50 times that means all my calls are gone?

phaseshift•2y ago

yup

GIGA BRAINOP•2y ago

NOOOOO hold on im gonna get another key

phaseshift•2y ago

suggest you then save the json data to local file 😄

GIGA BRAINOP•2y ago

oh yeah i never thought about that haha

GIGA BRAINOP•2y ago

GIGA BRAINOP•2y ago

here it is oh i see, so i can bypass the exception and write out whatever the value is still? but if its null wouldn't it just be nothing

daysleeper•2y ago

no here it throws an exception not a warning

GIGA BRAINOP•2y ago

oh my bad, i said it was a null warning i thought they were the same thing

phaseshift•2y ago

weatherResult being null means the json doesnt match the binding class - DailyForecast

GIGA BRAINOP•2y ago

oh so there IS something wrong with my property class ok i'll look into that some more

phaseshift•2y ago

you can paste the json here,https://quicktype.io/, or directly into visual studio, to get c# classes to match the json

Vi Ness•2y ago

The warning is the compiler telling you "Hey, this could be null but it prob'ly shouldn't be," warning you that there could be an exception. The exception is the runtime saying "This is null and I don't like it"

GIGA BRAINOP•2y ago

yeah i got one, someone recommended json2csharp.com i'm following the format, but i guess i did something wrong ah ok, so the warning leads to the exception

Vi Ness•2y ago

It just means that there could be an exception

GIGA BRAINOP•2y ago

oh i see what i did wrong now i completely forgot there was another sub-property in maximum and minimum 🤦‍♂️ wait im not sure anymore

GIGA BRAINOP•2y ago

GIGA BRAINOP•2y ago

this is what the documentation says

GIGA BRAINOP•2y ago

GIGA BRAINOP•2y ago

and this is what the converter recommends based off the json file this DOES mean that i need 2 more classes for minimum and maximum right?

Vi Ness•2y ago

The exception makes it sound like it's the Temperature object that didn't get deserialized correctly. Did the date print out correctly when you ran it?

GIGA BRAINOP•2y ago

yeah i think im starting to get it i need to struggle with it a little more but yeah i think the temperature object is the problem

Vi Ness•2y ago

The first thing I would try is changing the Value properties on Minimum and Maximum (realistically they should be the same class) to double instead of int. The values in the Json have decimal points so idk why the converter recommends int.

GIGA BRAINOP•2y ago

i'm stumped, i thought i had it but i guess i didn't i've been trying to figure this out for a while but i just cant seem to get it right i changed up my classes to reflect the documentation and the json class converter, but i can't access any of the results

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WeatherApp
{
    public class newRoot
    {
        public List<DailyForecast> DailyForecasts { get; set; }
    }

    public class DailyForecast
    {
        public string Date { get; set; }
        public Temperature Temperature { get; set; }
    }

    public class Maximum
    {
        public double Value { get; set; }
        public string Unit { get; set; }
    }

    public class Minimum
    {
        public double Value { get; set; }
        public string Unit { get; set; }
    }

    public class Temperature
    {
        public Minimum Minimum { get; set; }
        public Maximum Maximum { get; set; }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WeatherApp
{
    public class newRoot
    {
        public List<DailyForecast> DailyForecasts { get; set; }
    }

    public class DailyForecast
    {
        public string Date { get; set; }
        public Temperature Temperature { get; set; }
    }

    public class Maximum
    {
        public double Value { get; set; }
        public string Unit { get; set; }
    }

    public class Minimum
    {
        public double Value { get; set; }
        public string Unit { get; set; }
    }

    public class Temperature
    {
        public Minimum Minimum { get; set; }
        public Maximum Maximum { get; set; }
    }
}

GIGA BRAINOP•2y ago

GIGA BRAINOP•2y ago

i keep getting this error in the code but in the documentation the api i'm calling says it returns an array, and i was able to turn the json into a list previously I've tried using var weatherResult = await client.GetStringAsync(link); and printing out weatherResult, but then my program won't even run due to build errors

Vi Ness•2y ago

I see you removed the &q={cityInput} from your link and the int UnitType from the Minimum and Maximum classes. Is that right?

GIGA BRAINOP•2y ago

well i plan on adding back cityInput later when i get the json deserialization and printing all correct and i did remove the int UnitType

Vi Ness•2y ago

Ah okay, so the API still returns a json if you don't provide a city?

GIGA BRAINOP•2y ago

i removed stuff i didn't want from the json so in this link http://dataservice.accuweather.com/forecasts/v1/daily/5day/2178895?apikey= the 2178895 is the location key i'm able to get from

var link = $"http://dataservice.accuweather.com/locations/v1/cities/search?apikey={key}&q={cityInput}";

// Get JSON results and deserialize
var citySearch = await client.GetFromJsonAsync<List<Root>>(link);

// Print results
foreach (Root root in citySearch)
{
    Console.WriteLine($"\nCity key: {root.Key}");
    Console.WriteLine($"{root.EnglishName}, {root.AdministrativeArea.EnglishName}, {root.PrimaryPostalCode}");
    Console.WriteLine($"Timezone: {root.TimeZone.Name}");
    Console.WriteLine($"Latitude: {root.GeoPosition.Latitude} Longitude: {root.GeoPosition.Longitude}");
}

var link = $"http://dataservice.accuweather.com/locations/v1/cities/search?apikey={key}&q={cityInput}";

// Get JSON results and deserialize
var citySearch = await client.GetFromJsonAsync<List<Root>>(link);

// Print results
foreach (Root root in citySearch)
{
    Console.WriteLine($"\nCity key: {root.Key}");
    Console.WriteLine($"{root.EnglishName}, {root.AdministrativeArea.EnglishName}, {root.PrimaryPostalCode}");
    Console.WriteLine($"Timezone: {root.TimeZone.Name}");
    Console.WriteLine($"Latitude: {root.GeoPosition.Latitude} Longitude: {root.GeoPosition.Longitude}");
}

the api i'm using (accuweather) has a flowchart where it says to get the city key from the location api and then use that city key to call the forecast api where i can get the weather the current flow of my program is able to get the city's general information as seen in the foreach loop and since there are multiple cities with the same name in different countries, i'll have the user enter in their desired city key which will then output all the weather but im having trouble with accessing the weather in the first palce i thought it would be as simple as this code i just posted since in the documentation it says they both return an array

GIGA BRAINOP•2y ago

GIGA BRAINOP•2y ago

GIGA BRAINOP•2y ago

my current thought process is that my problem is stemming from my newRoot class, where it's a list of the DailyForecast type called DailyForecasts honestly idk, im just stumped

Vi Ness•2y ago

I'd start with just trying to get the json string from the api into the console as text to make sure you're calling the api correctly. Once you have that working we can focuus on deserializing them

GIGA BRAINOP•2y ago

and i would do that through GetStringAsync right?

link = $"http://dataservice.accuweather.com/forecasts/v1/daily/5day/2178895?apikey={key}";

var weatherResult = await client.GetStringAsync(link);

Console.WriteLine(weatherResult);

link = $"http://dataservice.accuweather.com/forecasts/v1/daily/5day/2178895?apikey={key}";

var weatherResult = await client.GetStringAsync(link);

Console.WriteLine(weatherResult);

when i try to run this code, my app won't even run at all, saying there were build errors

Vi Ness•2y ago

What are the build errors?

GIGA BRAINOP•2y ago

nevermind im dumb i didn't see that i didnt comment out a curly brace

GIGA BRAINOP•2y ago

GIGA BRAINOP•2y ago

yup im able to get the json this doesn't look like an array straight up to me

Vi Ness•2y ago

It looks like there's a Headline and then an array of DailyForecasts

GIGA BRAINOP•2y ago

do i need to include headline in my property class? i was told that i could omit properties that i didn't plan on including in my classes when dealing with apis

Vi Ness•2y ago

You can omit them, yeah. I've only dealt with deserialization with Newtonsoft.Json and making my models like this where you specify what each thing is called in the json file

GIGA BRAINOP•2y ago

ooh i see i've heard about newtonsoft.json, is it widely used? maybe i should switch over to that

Vi Ness•2y ago

I think it's one of, if not the most downloaded nuget package

GIGA BRAINOP•2y ago

would i run into the same problem i'm having right now even if i used newtson soft though? surely this is a logic problem im just not understanding

Vi Ness•2y ago

Prob'ly. I was just sharing what I have experience with

GIGA BRAINOP•2y ago

fair, definitely gonna look into that later

GIGA BRAINOP•2y ago

looking at the json in the formatter, i can see that dailyforecast is indeed an array

GIGA BRAINOP•2y ago

and it would seem that my classes are correct according to the converter, also taking into account making changes according to the documentation of the api

Vi Ness•2y ago

What happens if you try to deserialize it now?

GIGA BRAINOP•2y ago

so just to make sure,

var weatherResult = await client.GetFromJsonAsync<List<newRoot>>(link);

var weatherResult = await client.GetFromJsonAsync<List<newRoot>>(link);

this line of code makes sense right?

    public class newRoot
    {
        public List<DailyForecast> DailyForecasts { get; set; }
    }

    public class newRoot
    {
        public List<DailyForecast> DailyForecasts { get; set; }
    }

referencing this ^

Vi Ness•2y ago

Shouldn't there be only one newRoot? Or is it giving you multiple in one call?

GIGA BRAINOP•2y ago

yeah i only have one newRoot

GIGA BRAINOP•2y ago

GIGA BRAINOP•2y ago

if i run that code i get this

Vi Ness•2y ago

You're trying to deserialize it into a List<newRoot>

GIGA BRAINOP•2y ago

yup

Vi Ness•2y ago

But there's only one

GIGA BRAINOP•2y ago

huh? im confused

Vi Ness•2y ago

GetFromJsonAsync<List<newRoot>(link) means you're trying to read an array of newRoot from the string. But the string is not an array of newRoot, it's only one

GIGA BRAINOP•2y ago

i think i get what youre trying to say? so in this case, when im using <List<newRoot>>: i'm assuming that the entire json ouput is an array when in reality it isn't entirely an array?

Vi Ness•2y ago

Right. The only array part of the Json is the DailyForecasts, which are part of newRoot

GIGA BRAINOP•2y ago

aiya so then i need to figure out how to deserialize the whole thing

Vi Ness•2y ago

You need to figure out how to derserialize the one thing

GIGA BRAINOP•2y ago

and by one thing do you mean the json output?

Vi Ness•2y ago

I mean the newRoot

GIGA BRAINOP•2y ago

isn't it not just a matter of removing the <list>?

Vi Ness•2y ago

It is exactly that

GIGA BRAINOP•2y ago

then i have the newRoot object that is retrieved and deserialized NICE

Vi Ness•2y ago

You're only trying to read one newRoot, not a list of them

GIGA BRAINOP•2y ago

and again i know that its only ONE newRoot since the entire output isn't an array?

Vi Ness•2y ago

Yeah

GIGA BRAINOP•2y ago

got it so now i just need to output the result when i run the code with console.WriteLine(weatherResult.DailyForecasts)

GIGA BRAINOP•2y ago

GIGA BRAINOP•2y ago

i see that it's a list but when i try printing out the contents in a foreach loop, i can't do so

Vi Ness•2y ago

Do you know how to set breakpoint and debug your variables?

GIGA BRAINOP•2y ago

yes and no? in this case would i set the breakpoint on this line?

var weatherResult = await client.GetFromJsonAsync<newRoot>(link);

var weatherResult = await client.GetFromJsonAsync<newRoot>(link);

and then just hover over it when it reaches that point to see the values?

Vi Ness•2y ago

Since we know that it's not crashing, I'd set the breakpoint after that and inspect your weatherResult variable to see what's in it

GIGA BRAINOP•2y ago

got it yup the values are there let me try and get a sc

GIGA BRAINOP•2y ago

Vi Ness•2y ago

That looks good. You've got 5 DailyForecasts in that array

GIGA BRAINOP•2y ago

i'm just confused why in the autocomplete it doesn't give me these options to add to the code yup the api i'm calling gets the forecast for 5 days WAIT do i just need to do Console.WriteLine(weatherResult.DailyForecasts[0]); ok amybe not it didnt work

Vi Ness•2y ago

That'll prob'ly just output WeatherApp.DailyForecast

GIGA BRAINOP•2y ago

oh wait now the property options are coming up

Vi Ness•2y ago

Mmhmm, cuz now you're accessing the DailyForecast that's in the List

GIGA BRAINOP•2y ago

IT WORKS it completely slipped my mind to access the array values but obviously i should've since it's an array lol THANK YOU VERY MUCH i appreciate all your help🤝

Vi Ness•2y ago

Np, now you get to do fun stuff with all your weather data~

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Null warning from accessing weather results from an API call