Declaring a variable of type map[string]map[string]... is not ideal, is there a better way
snaps := map[string]map[string]map[string]map[string]string{
"distros": {
"aws": {
"eu-west-1": {
"snap-0": "/dev/sdm",
},
"eu-west-2": {
"snap-1": "/dev/sdm",
},
},
},
}
fmt.Println(snaps["distros"]["aws"]["eu-west-1"])
The simplest way would be to use the type map[string]interface{}. Since the empty interface, interface{}, refers to any type and therefore handles the arbitrarily nested nature of JSON.
To do this you'll have to write your literal data as a string first and then parse the string into a Go map.
With that in mind here is a refactor of your example:
first: import "encoding/json", then
snapsStr := `{
"distros": {
"aws": {
"eu-west-1" : {
"snap-0": "/dev/sdm"
},
"eu-west-2": {
"snap-1": "/dev/sdm"
}
}
}
}`
var snaps map[string]interface{}
json.Unmarshal([]byte(snapsStr), &snaps)
And now snaps is as desired.
This is the most generic format for JSON data in Go and is one of the ways that the Go JSON library handles types for JSON. See these docs: https://golang.org/pkg/encoding/json/#Unmarshal
Related
I wanted to clarify how to set values for
type ElkBulkInsert struct {
Index []struct {
_Index string `json:"_index"`
_Id string `json:"_id"`
} `json:"index"`
}
to make json.Marshall
there were no problems for the usual structure
package main
import (
"encoding/json"
"fmt"
)
type ElkBulkInsert struct {
Index []struct {
_Index string `json:"_index"`
_Id string `json:"_id"`
} `json:"index"`
}
type ElkBulIsertUrl struct {
Url string `json:"url"`
}
func main() {
sf := ElkBulIsertUrl{
Url: "http://mail.ru",
}
dd, _ := json.Marshal(sf)
fmt.Println(string(dd))
}
It's really unclear what you're asking here. Are you asking why the JSON output doesn't match what you expect? Are you unsure how to initialise/set values on the Index field of type []struct{...}?
Because it's quite unclear, I'll attempt to explain why your JSON output may appear to have missing fields (or why not all fields are getting populated), how you can initialise your fields, and how you may be able to improve the types you have.
General answer
If you want to marshal/unmarshal into a struct/type you made, there's a simple rule to keep in mind:
json.Marshal and json.Unmarshal can only access exported fields. An exported field have Capitalised identifiers. Your Index fieldin the ElkBulkInsert is a slice of an anonymous struct, which has no exported fields (_Index and _Id start with an underscore).
Because you're using the json:"_index" tags anyway, the field name itself doesn't have to even resemble the fields of the JSON itself. It's obviously preferable they do in most cases, but it's not required. As an aside: you have a field called Url. It's generally considered better form to follow the standards WRT initialisms, and rename that field to URL:
Words in names that are initialisms or acronyms (e.g. "URL" or "NATO") have a consistent case. For example, "URL" should appear as "URL" or "url" (as in "urlPony", or "URLPony"), never as "Url". Here's an example: ServeHTTP not ServeHttp.
This rule also applies to "ID" when it is short for "identifier," so write "appID" instead of "appId".
Code generated by the protocol buffer compiler is exempt from this rule. Human-written code is held to a higher standard than machine-written code.
With that being said, simply changing the types to this will work:
type ElkBulkInsert struct {
Index []struct {
Index string `json:"_index"`
ID string `json:"_id"`
} `json:"index"`
}
type ElkBulIsertUrl struct {
URL string `json:"url"`
}
Of course, this implies the data for ElkBulkInsert looks something like:
{
"index": [
{
"_index": "foo",
"_id": "bar"
},
{
"_index": "fizz",
"_id": "buzz"
}
]
}
When you want to set values for a structure like this, I generally find it easier to shy away from using anonymous struct fields like the one you have in your Index slice, and use something like:
type ElkInsertIndex struct {
ID string `json:"_id"`
Index string `json:"_index"`
}
type ElkBulkInsert struct {
Index []ElkInsertIndex `json:"index"`
}
This makes it a lot easier to populate the slice:
bulk := ElkBulkInsert{
Index: make([]ElkInsertIndex, 0, 10), // as an example
}
for i := 0; i < 10; i++ {
bulk.Index = append(bulk.Index, ElkInsertIndex{
ID: fmt.Sprintf("%d", i),
Index: fmt.Sprintf("Idx#%d", i), // wherever these values come from
})
}
Even easier (for instance when writing fixtures or unit tests) is to create a pre-populated literal:
data := ElkBulkInsert{
Index: []ElkInsertIndex{
{
ID: "foo",
Index: "bar",
},
{
ID: "fizz",
Index: "buzz",
},
},
}
With your current type, using the anonymous struct type, you can still do the same thing, but it looks messier, and requires more maintenance: you have to repeat the type:
data := ElkBulkInsert{
Index: []struct{
ID string `json:"_id"`
Index string `json:"_index"`
} {
ID: "foo",
Index: "bar",
},
{ // you can omit the field names if you know the order, and initialise all of them
"fizz",
"buzz",
},
}
Omitting field names when initialising in possible in both cases, but I'd advise against it. As fields get added/renamed/moved around over time, maintaining this mess becomes a nightmare. That's also why I'd strongly suggest you use move away from the anonymous struct here. They can be useful in places, but when you're representing a known data-format that comes from, or is sent to an external party (as JSON tends to do), I find it better to have all the relevant types named, labelled, documented somewhere. At the very least, you can add comments to each type, detailing what values it represents, and you can generate a nice, informative godoc from it all.
I'm currently looking at adding Pact testing into my Go code, and i'm getting stuck on how to deal with field types of UUID.
I have the following struct, which I use to deserialise a response from an API to
import (
"github.com/google/uuid"
)
type Foo struct {
ID uuid.UUID `json:"id"`
Name string `json:"name"`
Description string `json:"description"`
}
Now, when I try and write my consumer test, it looks something like this
pact.
AddInteraction().
Given("A result exists").
UponReceiving("A request to get all results").
WithRequest(dsl.Request{
Method: "get",
Path: dsl.String("/v1"),
}).
WillRespondWith(dsl.Response{
Status: 200,
Headers: dsl.MapMatcher{"Content-Type": dsl.String("application/json")},
Body: dsl.Match(&Foo{}),
})
The problem now, is the mocked response comes through as below, where it tries to put an array of bytes in the "id" field, I'm assuming since behind the scenes that is what the google/uuid library stores it as.
{
"id": [
1
],
"name": "string",
"description": "string"
}
Has anyone encountered this? And what would be the best way forward - the only solution I can see is changing my model to be a string, and then manually convert to a UUID within my code.
You currently can't use the Match function this way, as it recurses non primitive structures, albeit it should be possible to override this behaviour with struct tags. Could you please raise a feature request?
The simplest approach is to not use the Match method, and just manually express the contract details in the usual way.
The internal representation of uuid.UUID is type UUID [16]byte but json representation of UUID is string
var u uuid.UUID
u, _ = uuid.Parse("f47ac10b-58cc-0372-8567-0e02b2c3d479")
foo1 := Foo{u, "n", "d"}
res, _ := json.Marshal(foo1)
fmt.Println(string(res))
{
"id": "f47ac10b-58cc-0372-8567-0e02b2c3d479",
"name": "n",
"description": "d"
}
and then load marshaled []byte
var foo Foo
json.Unmarshal(res, &foo)
Currently I have the following definition for my structs:
type WholeJson struct {
Features []Temp
}
type Temp struct {
Properties Human
}
type Human struct {
Name string
Age uint
}
Which is working when unmarshaling a JSON string into a variable of type WholeJson, which would have the following structure:
{
"features":[
{
"properties": {
"name": "John Doe",
"age": 50
}
}
]
}
Go Playground sample here: https://play.golang.org/p/3WTLxR0EZWP
But I don't know how to write it in a simpler way. It is obvious that not both WholeJson and Temp are necessary as far as using the information they will hold. The only reason I have Temp is because I simply don't know how to avoid defining it (and still have the program work).
Presumably the Features property of WholeJson would have an array to some interface{}, but I can't nail the syntax. And I'm assuming the code for reading the unmarshalled data (from the playground sample) will stay the same.
How would I "squash" those those two structs into one (the Human struct i'm assuming is okay if it stays on its own), and still have useful data in the end, where I could loop through the features key to go through all the data?
It's OK to define a type for each level of the hierarchy and preferred when constructing values from Go code. The types do not need to be exported.
Use anonymous types to eliminate the defined types:
var sourceData struct {
Features []struct {
Properties Human
}
}
var jsonString string = `{
"features":[
{
"properties": {
"name": "John Doe",
"age": 50
}
}
]
}`
json.Unmarshal([]byte(jsonString), &sourceData)
fmt.Println(sourceData.Features[0].Properties.Name)
Hi there Golang experts,
I am using the Machinebox "github.com/machinebox/graphql" library in golang as client for my GraphQL server.
Mutations with single layer JSON variables work just fine
I am, however, at a loss as to how to pass a nested JSON as a variable
With a single layer JSON I simply create a map[string]string type and pass into the Var method. This in turn populates my graphql $data variable
The machinebox (graphql.Request).Var method takes an empty interface{} as value so the map[string]string works fine. But embedded json simply throws an error.
code:
func Mutate(data map[string]string, mutation string) interface{} {
client := GQLClient()
graphqlRequest := graphql.NewRequest(mutation)
graphqlRequest.Var("data", data)
var graphqlResponse interface{}
if err := client.Run(context.Background(), graphqlRequest, &graphqlResponse); err != nil {
panic(err)
}
return graphqlResponse
}
Mutation:
mutation createWfLog($data: WfLogCreateInput)
{
createWfLog (data: $data){
taskGUID {
id
status
notes
}
event
log
createdBy
}
}
data variable shape:
{
"data": {
"event": "Task Create",
"taskGUID": {
"connect": {"id": "606f46cdbbe767001a3b4707"}
},
"log": "my log and information",
"createdBy": "calvin cheng"
}
}
As mentioned, the embedded json (value of taskGUID) presents the problem. If value was simple string type, it's not an issue.
Have tried using a struct to define every nesting, passed in struct.
Have tried unmarshaling a struct to json. Same error.
Any help appreciated
Calvin
I have figured it out... and it is a case of my noobness with Golang.
I didn't need to do all this conversion of data or any such crazy type conversions. For some reason I got in my head everything HAD to be a map for the machinebox Var(key, value) to work
thanks to xarantolus's referenced site I was able to construct a proper strut. I populated the strut with my variable data (which was a nested json) and the mutation ran perfectly!
thanks!
I have following GraphQLEnumType
const PackagingUnitType = new GraphQLEnumType({
name: 'PackagingUnit',
description: '',
values: {
Carton: { value: 'Carton' },
Stack: { value: 'Stack' },
},
});
On a mutation query if i pass PackagingUnit value as Carton (without quotes) it works. But If i pass as string 'Carton' it throws following error
In field "packagingUnit": Expected type "PackagingUnit", found "Carton"
Is there a way to pass the enum as a string from client side?
EDIT:
I have a form in my front end, where i collect the PackagingUnit type from user along with other fields. PackagingUnit type is represented as a string in front end (not the graphQL Enum type), Since i am not using Apollo Client or Relay, i had to construct the graphQL query string by myself.
Right now i am collecting the form data as JSON and then do JSON.stringify() and then remove the double Quotes on properties to get the final graphQL compatible query.
eg. my form has two fields packagingUnitType (An GraphQLEnumType) and noOfUnits (An GraphQLFloat)
my json structure is
{
packagingUnitType: "Carton",
noOfUnits: 10
}
convert this to string using JSON.stringify()
'{"packagingUnitType":"Carton","noOfUnits":10}'
And then remove the doubleQuotes on properties
{packagingUnitType:"Carton",noOfUnits:10}
Now this can be passed to the graphQL server like
newStackMutation(input: {packagingUnitType:"Carton", noOfUnits:10}) {
...
}
This works only if the enum value does not have any quotes. like below
newStackMutation(input: {packagingUnitType:Carton, noOfUnits:10}) {
...
}
Thanks
GraphQL queries can accept variables. This will be easier for you, as you will not have to do some tricky string-concatenation.
I suppose you use GraphQLHttp - or similar. To send your variables along the query, send a JSON body with a query key and a variables key:
// JSON body
{
"query": "query MyQuery { ... }",
"variables": {
"variable1": ...,
}
}
The query syntax is:
query MyMutation($input: NewStackMutationInput) {
newStackMutation(input: $input) {
...
}
}
And then, you can pass your variable as:
{
"input": {
"packagingUnitType": "Carton",
"noOfUnits": 10
}
}
GraphQL will understand packagingUnitType is an Enum type and will do the conversion for you.