Golang Mutation with a list as a param variable (GRAPHQL) - go

Question

Basically what im trying to do is send a list of string ex: ["aa","bb","vv"] into a graphql Mutation field, currently this is my Mutation Schema
"listTest": &graphql.Field{
Type: QueryMessageType,
Args: graphql.FieldConfigArgument{
"listNew": &graphql.ArgumentConfig{
Description: "Example List of Json String",
Type: graphql.NewList(graphql.NewNonNull(graphql.String)),
},
},
Resolve: func(p graphql.ResolveParams) (interface{}, error) {
list := p.Args["listTest"].([]string)
return listTest(list)
},
},
and the Method listTest
func listTest(testing[]string) (*QueryMessage, error) {
fmt.Println(testing)
return &QueryMessage{
QueryBody: "nothing to do here",
}, nil
}
However when i do the request in INSOMNIA the response is:
{
"data": {
"listTest": null
},
"errors": [
{
"message": "interface conversion: interface {} is []interface {}, not []string",
"locations": []
}
]
}
and the request is this:
mutation{
listTest(listNew: ["aa","bb","vv"]){
querybody
}
}
can anyone tell me how to receive a List of String in my Go Server. Thanks! :)
UPDATE
When i call a fmt.Println(p.Args["listTest"])
the result is: [aa bb vv]
SOLVED
Following the instructions of the voted answer, the script now do his job. This is the final result:
Resolve: func(p graphql.ResolveParams) (interface{}, error) {
var groupIDs []string
for _, gid := range p.Args["list"].([]interface{}) {
groupIDs = append(groupIDs, gid.(string))
}
for _, final := range groupIDs {
fmt.Println(final)
}
return listTest(groupIDs)
},
and in the console i got this:
aa
bb
vv

Answer 1

Your problem, according to the error message, is with this line:
list := p.Args["listTest"].([]string)
p.Args["listTest"] is returning []interface{}.
interface{} can store any other type. If you are familiar with java it's a little bit like Object.
The problem here is that you have your field from p.Args["listTest"] and you are trying to type assert it to []string. This would work if the value stored in args were interface{} (any). But it's not, p.Args (according to the error) holds []interface{}. This is a slice of interface values, where each of those can be anything (rather than a single interface value holding a slice of strings.)
Instead try ranging over that list of interfaces, and type asserting each value.
var strs []string
for _, v := range p.Args["list"].([]interface{}) {
strs = append(strs, v.(string))
}
Or investigate another way to set up the graphQL types so that you get the values back in a more useable way.