I got this error: type 'String' is not a subtype of type 'Null' in get method flutter
this is the get api function that i use
Future<Stream<ServiceTypes>> getServiceTypesa() async {
final String url = 'https://test.com';
final client = new http.Client();
final streamedRest = await client.send(
http.Request('get', Uri.parse(url))
);
return streamedRest.stream
.transform(utf8.decoder)
.transform(json.decoder)
.expand((data) => (data as List))
.map((data) => ServiceTypes.fromJson(data));
}
you can see here the function detect the data
i saw also this error
StateError (Bad state: Stream has already been listened to.)
and this error
this is my listen function
#override
void initState() {
_serviceTypes = new List<ServiceTypes>();
listenForServiceTypes();
super.initState();
}
void listenForServiceTypes() async {
setState(() {
this._show_serviceTypesProgress = true;
});
final Stream<ServiceTypes> stream = await getServiceTypesa();
stream.listen((ServiceTypes serviceTypes) =>
setState(() => _serviceTypes.add(serviceTypes)));
setState(() {
this._show_serviceTypesProgress = false;
});
print(_serviceTypes);
}
this is the model that i made
I don't know what is the problem because the print function return : []
When you create model, the image type value is null so, the model is create with Null type of image but when images are not null type from server then it gives you an error
type 'String' is not a subtype of type 'Null' in get method flutter
because your image type is String from server and you get value by Null Object, So use String type object for getting string value or images.
Use this
Class ServiceTypes{
String image;
instead of
Class ServiceTypes{
Null image;
As extra information, you can check the keys name. I faced the same problem just because I tried to fetch a key not found.
In the first time I wrote content instead of details and in my API I have details not content.
have a good day :)
The issue is clear, you define image type as Null then trying to pass string to it, try to change definition.. like so:
Class ServiceTypes{
int id;
String name;
String image;
...
use ? this for nullable key. For example :
final String? title;
final String? category;
here is the complete solution :
Is it possible to parse json in Flutter/Dart with missing attributes (keys of json data)?
Related
I am learning Flutter. This is the string that I need to call and I don't know how to call this type of string.
{
"Info":[
{
"c_type_id":"1",
"cleaning type":"Washroom Cleaning"
},
{
"c_type_id":"2",
"cleaning type":"Garden\/Lawn Cleaning"
}
]
}
My code
class Album {
final String title;
Album({
this.title,
});
factory Album.fromJson(Map<String, dynamic> json) {
return Album(
title: json['title'],
);
}
}
As I am following my code like this https://flutter.dev/docs/cookbook/networking/fetch-data
and got this error "A non-null String must be provided to a Text widget." because they are following this type of string and my string type is different. Help!
{
"userId": 1,
"id": 1,
"title": "quidem molestiae enim"
}
Your given data (API response) seems to have a list of maps, so you should get the data first (use async function):
var response = await http.get("Your Url")
then you should extract the given map list as follow:
var temp = json.decode(response);
List<dynamic> result = temp['Info']); // it is the described list
now, you can use your data (extract each parameter):
String c_type_id = result[0]['c_type_id'];
// and so on...
Your question is not clear at all but I can show you an example how to reach an element in a json.
Your json consists a list that contains string keys. To reach first element of list;
json["Info"][0]
Then pass the key you want to get its value;
json["Info"][0]["c_type_id"]
http_requests All type of http requests are mentioned in this post. If you have any further problem kindly make comment.
I'm passing a model to an API action with a property called eventType which is a nullable custom enum.
If I pass a random value for eventType, such as 'h', it fails to serialise which is correct.
However, the error I get from the ModelState is not something I would want a public caller to see. It includes the line number and position (see below).
I've tried a number of options including a custom data annotation with no success.
Does anyone know how I could define a nicer custom message?
"Error converting value \"h\" to type
'System.Nullable`1[Custom.EventTypes]'. Path 'eventType', line 1,
position 80."
Most times the first error is usually the most important error or rather one that describes the situation properly. You can use this way to manipulate to get the first error message from the first key or change it to whatever you want if you wish to get all the error messages.
public ActionResult GetMyMoney(MyModel myModel)
{
string nss = ModelState.First().Key;
ModelError[] ern = ModelState[nss].Errors.ToArray();
string ndd = ern.First().ErrorMessage;
}
public class CustomFilter: IAsyncActionFilter
{
public async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
{
if (!context.ModelState.IsValid)
{
// You can pass custom object to BadRequestObjectResult method
context.Result = new BadRequestObjectResult(customObject);
}
}
}
You can write a custom filter like above mentioned and pass a custom object with your message.
Ref: this
IF you just want the error messages you can simply create a custom class of response and then
var response = new ResponseApi{
StatusCode = HttpStatusCode.BadRequest,
Message = "Validation Error",
Response = ModelState.Values.SelectMany(x => x.Errors).Select(x =>
x.ErrorMessage)
};
then just return the response or create a validation filter to handle validations globally.
/// <summary>
/// Validatation filter to validate all the models.
/// </summary>
public class ValidationActionFilter : ActionFilterAttribute
{
/// <inheritdoc/>
public override void OnActionExecuting(HttpActionContext actionContext)
{
ModelStateDictionary modelState = actionContext.ModelState;
if (!modelState.IsValid)
{
actionContext.Response = SendResponse(new ResponseApi
{
StatusCode= 400,
Message = "Validation Error",
Response = modelState.Values.SelectMany(x =>
x.Errors).Select(x => x.ErrorMessage)
});
}
}
private HttpResponseMessage SendResponse(ResponseApiresponse)
{
var responseMessage = new HttpResponseMessage
{
StatusCode = (HttpStatusCode)response.StatusCode,
Content = new StringContent(JsonConvert.SerializeObject(response)),
};
responseMessage.Content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
return responseMessage;
}
}
I am trying to execute multiGet function in Spring on Redis. It throws me an error. I have implemented get function successfully but while implementing multiGet it asks me for a Collection as second parameter. I am not sure what to enter? Can someone please guide me here.
Here is my code for multiGet()
Method definition:
#Override
public User findById_MultiGet(String id) {
return (User)hashOperations.multiGet("USER", id);
}
Code In Controller :
#GetMapping("Map/MultiGet/{id}")
public User allMultiGet(#PathVariable("id") final String id) {
// MultiGet function
return userRepository.findById_MultiGet(id);
}
Error for above multiget method is multiget(Object, Collection) type not (String,String) type
Below code for Get function is working.
public User findById(String id) {
return (User)hashOperations.get("USER", id);
}
Code In Controller for Get function :
#GetMapping("Map/Get/{id}")
public User allGet(#PathVariable("id") final String id) {
// Get function
return userRepository.findById(id);
}
For multiGet the second parameter should be a Collection like a List (in case you want the values of the list returned as result on the same positions as their belonging keys in the input list) or a Set.
In your example this would be something like this:
List<Object> values = hashOperations.multiGet("USER", Arrays.asList("id", "name"));
Object id = values.get(0);
Object name = values.get(1);
I validate the input using ModelState.IsValid:
[HttpGet]
[Route("subjects")]
[ValidateAttribute]
public IHttpActionResult GetSubjects(bool? isActive = null)
{
//get subjects
}
If I pass in the uri ~/subjects/?isActive=abcdef, I get the error message:
The value 'abcdef' is not valid for Nullable`1.
If the input parameter is not nullable
public IHttpActionResult GetSubjects(bool isActive){
//get subjects
}
I get the error message:
The value 'abcdef' is not valid for Boolean.
I want to override the message if nullable type so I can maintain the message ("The value 'abcdef' is not valid for Boolean."). How can I do this since in the ModelState error I don't get the data type. I am implementing the validation as a custom ActionFilterAttribute (ValidationAttribute).
You can change callback that formats type conversion error messages. For example, let's define it right into Global.asax.cs:
public class WebApiApplication : HttpApplication
{
protected void Application_Start()
{
ModelBinderConfig.TypeConversionErrorMessageProvider = this.NullableAwareTypeConversionErrorMessageProvider;
// rest of your initialization code
}
private string NullableAwareTypeConversionErrorMessageProvider(HttpActionContext actionContext, ModelMetadata modelMetadata, object incomingValue)
{
var target = modelMetadata.PropertyName;
if (target == null)
{
var type = Nullable.GetUnderlyingType(modelMetadata.ModelType) ?? modelMetadata.ModelType;
target = type.Name;
}
return string.Format("The value '{0}' is not valid for {1}", incomingValue, target);
}
}
For not nullable types Nullable.GetUnderlyingType will return null, in this case we will use original type.
Unfortunately you cannot access default string resources and if you need to localize error message you must do it on your own.
Another way is to implement your own IModelBinder, but this is not a good idea for your particular problem.
Lorond's answer highlights how flexible asp.net web api is in terms of letting a programmer customize many parts of the API. When I looked at this question, my thought process was to handle it in an action filter rather than overriding something in the configuration.
public class ValidateTypeAttribute : ActionFilterAttribute
{
public ValidateTypeAttribute() { }
public override void OnActionExecuting(HttpActionContext actionContext)
{
string somebool = actionContext.Request.GetQueryNameValuePairs().Where(x => x.Key.ToString() == "somebool").Select(x => x.Value).FirstOrDefault();
bool outBool;
//do something if somebool is empty string
if (!bool.TryParse(somebool, out outBool))
{
HttpResponseMessage response = new HttpResponseMessage(System.Net.HttpStatusCode.BadRequest);
response.ReasonPhrase = "The value " + somebool + " is not valid for Boolean.";
actionContext.Response = response;
}
else
{
base.OnActionExecuting(actionContext);
}
}
Then decorate the action method in the controller with the action filter attribute
I'm doing a message inspector in WCF:
public class LogMessageInspector :
IDispatchMessageInspector, IClientMessageInspector
which implements the method:
public object AfterReceiveRequest(ref Message request,
IClientChannel channel, InstanceContext instanceContext)
I can get the name of the invoked service with:
instanceContext.GetServiceInstance().GetType().Name
But how do I get the name of the invoked operation?
It's not pretty, but this is what I did to get the operation name:
var action = OperationContext.Current.IncomingMessageHeaders.Action;
var operationName = action.Substring(action.LastIndexOf("/", StringComparison.OrdinalIgnoreCase) + 1);
var operationName = OperationContext.Current.IncomingMessageProperties["HttpOperationName"] as string;
This approach is similar to others presented here, but uses Path.GetFileName:
Path.GetFileName(OperationContext.Current.IncomingMessageHeaders.Action);
The return value of this method and the format of the path string work quite harmoniously in this scenario:
The characters after the last directory character in path. If the last
character of path is a directory or volume separator character, this
method returns String.Empty. If path is null, this method returns
null.
OperationContext.Current.IncomingMessageHeaders.Action.Split('/').ToList().Last();
Little late to the party but I had to dig a little deeper than existing answers on this question because they seem to involve getting the action name and not the operation name. (Frequently they are the same so getting the action name does, in fact, get the operation name.)
Microsoft's Application Insights SDK Labs' WCF library makes this concerted effort:
private string DiscoverOperationName(OperationContext operationContext)
{
var runtime = operationContext.EndpointDispatcher.DispatchRuntime;
string action = operationContext.IncomingMessageHeaders.Action;
if (!string.IsNullOrEmpty(action))
{
foreach (var op in runtime.Operations)
{
if (op.Action == action)
{
return op.Name;
}
}
}
else
{
// WebHttpDispatchOperationSelector will stick the
// selected operation name into a message property
return this.GetWebHttpOperationName(operationContext);
}
var catchAll = runtime.UnhandledDispatchOperation;
if (catchAll != null)
{
return catchAll.Name;
}
return "*";
}
private string GetWebHttpOperationName(OperationContext operationContext)
{
var name = WebHttpDispatchOperationSelector.HttpOperationNamePropertyName;
if (this.HasIncomingMessageProperty(name))
{
return this.GetIncomingMessageProperty(name) as string;
}
return "<unknown>";
}