Json: Cannot Unmarshal Object into Go Value of Type
I Can't Decode the Json Code Below. .. Any Ideas Why It Doesn't Work? See Also Play. Golang Package Main Import ( "Encoding/Json" ) Type Locationreadable...
I can't decode the json code below ... any ideas why it doesn't work ? See also play.golang
package main
import (
"encoding/json"
)
type LocationReadable struct {
District string
City string
State string
}
type Locale struct {
Location string
CountryCode string
CurrencyId string
CurrencySymbol string
LocationReadable LocationReadable
}
type Media struct {
Image string
Video string
}
type Variations struct {
FixedPrice float64
Media Media
Quantity int
}
type PaymentData struct {
PaymentName string
PaymentService string
}
type Payment struct {
Online PaymentData
Offline PaymentData
}
type Shipping struct {
ShippingService string
ShippingName string
ShippingCost float64
HandlingTimeMax int
DispatchTimeMin int
DispatchTimeMax int
ShippingAdditionalCost int
}
type Item []struct {
_version string
CategoryId string
Title string
Media Media
SellerId string
Locale Locale
ListingType string
Payment Payment
StartTime string
EndTime string
Shipping Shipping
TitleSlug string
Variations Variations
_fpaiStatus string
}
func main() {
itemInfoR := `{"locale":{"location":"51.51121389999999,-0.11982439999997041","countryCode":"GB","currencyId":"GBP","currencySymbol":"£","locationReadable":{"district":"City of Westminster","city":"London","state":"Greater London"}},"_version":"serving","categoryId":["Root","Cameras \u0026 Photo","Digital Cameras"],"title":"many pictures","media":{"image":["//","//","//","//","//","//","//","//","//","//","//","//","//","//","//","//","//","//","//","//","//","//","//","//","//","//"],"video":[]},"sellerId":"mihai","listingType":"fixedPrice","payment":{"online":[{"paymentName":"PayPal","paymentService":"paypal"}],"offline":[{"paymentName":"Pay on Pick-up","paymentService":"payOnPickup"}]},"startTime":"2014-01-04T10:02:18+00:00","endTime":"2014-04-04T10:02:18+00:00","shipping":[{"shippingService":"economy","shippingName":"Economy","shippingCost":1.0,"handlingTimeMax":4,"dispatchTimeMin":1,"dispatchTimeMax":10,"shippingAdditionalCost":"2"},{"shippingService":"localPickup","shippingName":"Local Pick-Up","shippingCost":0.0,"handlingTimeMax":2,"dispatchTimeMin":0,"dispatchTimeMax":0,"shippingAdditionalCost":"0"}],"titleSlug":"many-pictures","variations":[{"fixedPrice":222999.0,"media":{"image":["//","//","//"],"video":[]},"quantity":1121,"Brand":"Bell \u0026 Howell"},{"fixedPrice":211.0,"media":{"image":["//","//","//","//"],"video":[]},"quantity":2,"Brand":"Fujifilm"},{"fixedPrice":22.0,"media":{"image":["//","//","//"],"video":[]},"quantity":12,"Brand":"Gateway"}],"_fpaiStatus":"published"}`
itemInfoBytes := []byte(itemInfoR)
var ItemInfo Item
er := json.Unmarshal(itemInfoBytes, &ItemInfo)
if er != nil {
panic(er)
}
}
6 Answers
Here's a fixed version of it:
The biggest fix that was needed is when Unmarshalling an array, that property needs to be an array/slice in the struct as well.
For example:
{ "things": ["a", "b", "c"] }
Would Unmarshal into a:
type Item struct {
Things []string
}
And not into:
type Item struct {
Things string
}
The other thing to watch out for when Unmarshaling is that the types line up exactly. It will fail when Unmarshalling a JSON string representation of a number into an int or float field -- "1" needs to Unmarshal into a string, not into an int like we saw with ShippingAdditionalCost int
Determining of root cause is not an issue since Go 1.8; field name now is shown in the error message:
json: cannot unmarshal object into Go struct field Comment.author of type string
You JSON doesn't match your struct fields: E.g. "district" in JSON and "District" as the field.
Also: Your Item is a slice type but your JSON is a dict value. Do not mix this up. Slices decode from arrays.
Just in case you're looking for an answer to this from an AWS perspective, particularly if you're trying to use UnmarshalListOfMaps() on the items coming back from a DynamoDB query(), then watch out for a simple typo I made.
Given that this function UnmarshalListOfMaps() takes in...a list of maps :-) then it needs to unmarshal into a List of whatever struct you're trying to build, and not just the plain struct itself. This was throwing me off because I was trying to start by querying for something that should only return one row.
movie := Movie{}
// Run the DynamoDB query
resp, err := session.Query(input) // type QueryInput
if err != nil {
log.WithError(err).Error("Error running DynamoDB query")
}
// Unmarshal all the attribute values into a Movie struct
err = dynamodbattribute.UnmarshalListOfMaps(resp.Items, &movie); if err != nil {
log.WithError(err).Error("Error marshaling DynamoDB result into Movie")
return link, err
}
The problem is in the first line. It should be movies := []Movie{} and then the reference &movie needs to change to &movies as well. If you leave it just as it is above, then the AWS Go SDK will throw this error:
cannot unmarshal list into Go value of type (etc).
If you ever face this while typing yml file not copy-pasting, it might be a problem with your yml file - mine was wrong indent. This happened while making pipeline on concourse.
The problem with me that i was using Timstamp in grpc specification and trying to send
grpcurl -d="{\"startDate\":{\"seconds\":\"1645237120\"},\"endDate\":{\"seconds\":\"1645937120\"},\"vin\":\"JH4DB1561NS000569\",\"customerId\":\"CUST12345\"}" -plaintext localhost:50051
i was getting that error
error getting request data: json: cannot unmarshal object into Go value of type string
when i change the time format to following: has solved the issue
grpcurl -d="{\"startDate\":\"2022-02-19T00:00:00Z\",\"endDate\":\"2022-02-20T00:00:00Z\",\"vin\":\"JH4DB1561NS000569\",\"customerId\":\"CUST12345\"}" -plaintext localhost:50051
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