type Old struct {
UserID int `json:"user_ID"`
Data struct {
Address string `json:"address"`
} `json:"old_data"`
}
type New struct {
UserID int `json:"userId"`
Data struct {
Address string `json:"address"`
} `json:"new_data"`
}
func (old Old) ToNew() New {
return New{
UserID: old.UserID,
Data: { // from here it says missing expression
Address: old.Data.Address,
},
}
}
What is "missing expression" error when using structs?
I am transforming old object to a new one. I minified them just to get straight to the point but the transformation is much more complex. The UserID field for example works great. But when I use struct (which intended to be a JSON object in the end) the Goland IDE screams "missing expression" and the compiler says "missing type in composite literal" on this line. What I am doing wrong? Maybe should I use something else instead of struct? Please help.
Data is an anonymous struct, so you need to write it like this:
type New struct {
UserID int `json:"userId"`
Data struct {
Address string `json:"address"`
} `json:"new_data"`
}
func (old Old) ToNew() New {
return New{
UserID: old.UserID,
Data: struct {
Address string `json:"address"`
}{
Address: old.Data.Address,
},
}
}
(playground link)
I think it'd be cleanest to create a named Address struct.
You're defining Data as an inline struct. When assigning values to it, you must first put the inline declaration:
func (old Old) ToNew() New {
return New{
UserID: old.UserID,
Data: struct {
Address string `json:"address"`
}{
Address: old.Data.Address,
},
}
}
Hence it is generally better to define a separate type for Data, just like User.
Related
Let's say I have two different structs:
type One struct {
Id string
// Other fields
}
type Two struct {
Id string
// Other fields
}
Is it possible to define a function that accepts both One and Two without explicitly listing them as options?
E.g. I am looking for something like this:
type ModelWithId struct {
Id string
}
func Test[M ModelWithId](m M) {
fmt.PrintLn(m.Id)
}
one := One { Id: "1" }
Test(one) // Prints 1
I don't want to use funcTest[M One | Two](m M), because I'll likely have 10+ structs and I don't want to come back to the function every time I add a new struct to the codebase.
Generics constraints the type parameter behaviours using methods, so you need to rewrite your code as:
type One struct {
id string
}
func (o *One) Id() string {
return o.id
}
then your use site would become:
type ModelWithId interface {
Id() string
}
func Test[M ModelWithId](m M) {
fmt.Println(m.Id())
}
I’m trying to post some JSON. Using the JSON-to-Go tool I have this struct defined:
type IssueSetState struct {
ID string `json:"id"`
CustomFields []struct {
Value struct {
Name string `json:"name"`
} `json:"value"`
Name string `json:"name"`
Type string `json:"$type"`
} `json:"customFields"`
}
I’m trying to populate it with some data that I can then pass into the http library:
jsonValues := &IssueSetState{
ID: resultEntityId.ID,
CustomFields: []{
Value: {
Name: "Fixed",
},
Name: "State",
Type: "StateIssueCustomField",
},
}
jsonEncoded := new(bytes.Buffer)
json.NewEncoder(jsonEncoded).Encode(jsonValues)
I keep getting errors like:
./main.go:245:19: syntax error: unexpected {, expecting type
./main.go:246:9: syntax error: unexpected :, expecting comma or }
./main.go:249:8: syntax error: unexpected : at end of statement
./main.go:251:4: syntax error: unexpected comma after top level declaration
I’m sure the mistake I’m making is a simple one, but I’m new to Go.
One possible way is to define named structs for every anonymous struct you have.
type IssueSetState struct {
ID string `json:"id"`
CustomFields []CustomField `json:"customFields"`
}
type CustomField struct {
Value Value `json:"value"`
Name string `json:"name"`
Type string `json:"type"`
}
type Value struct {
Name string `json:"name"`
}
Now you can create it like this:
IssueSetState{
ID: resultEntityId.ID,
CustomFields: []CustomField{
{
Value: Value{
Name: "Fixed",
},
Name: "State",
Type: "StateIssueCustomField",
},
{
Value: Value{
Name: "Fixed",
},
Name: "State",
Type: "StateIssueCustomField",
},
},
}
So you're initializing the jsonValue badly.
You can fix it in 2 ways:
https://play.golang.org/p/LFO4tOLyG60
making structures flat
https://play.golang.org/p/TyFfaMf7XeF
by repeating the structure definition when declaring value
The first one should be easier and clearer.
Recently I started experimenting with Go, but I hit on hard rock.
I have this type:
type LocationType string
const (
River LocationType = "River"
Mountain LocationType = "Mountain"
)
func (t LocationType) ToString() string {
return string(t)
}
I also have this one:
type LocationCreateInput struct {
Name string `json:"name,omitempty"`
Type *models.LocationType `json:"type,omitempty"`
}
Now I'm trying to create a new LocationCreateInput variable:
input := &gqlModels.LocationCreateInput {
Name: "Test name",
Type: models.River
}
and I am getting the below error:
Cannot use 'models.Site' (type LocationType) as the type *models.LocationType
Can somebody point me to the right way of assigning the Type value? In the end, it is just a string.
What am I missing here? Could you give me a push?
You are trying to assign a value to a pointer type. So it's not "just a string", it's a "a pointer to just a string".
Either you change the type of the struct field from *models.LocationType to models.LocationType, or you need to take the address when assigning:
val := models.River
input := &gqlModels.LocationCreateInput {
Name: "Test name",
Type: &val,
}
I created a struct in a file called availability.go
package restconsume
import (
)
// Availabilityrequest for sabre
type Availabilityrequest struct {
OTAAirLowFareSearchRQ struct {
OriginDestinationInformation []struct {
DepartureDateTime string `json:"DepartureDateTime"`
DestinationLocation struct {
LocationCode string `json:"LocationCode"`
} `json:"DestinationLocation"`
OriginLocation struct {
LocationCode string `json:"LocationCode"`
} `json:"OriginLocation"`
RPH string `json:"RPH"`
} `json:"OriginDestinationInformation"`
POS struct {
Source []struct {
PseudoCityCode string `json:"PseudoCityCode" default:"F9CE"`
RequestorID struct {
CompanyName struct {
Code string `json:"Code" default:"TN"`
} `json:"CompanyName"`
ID string `json:"ID" default:"1"`
Type string `json:"Type" default:"1"`
} `json:"RequestorID"`
} `json:"Source"`
} `json:"POS"`
TPAExtensions struct {
IntelliSellTransaction struct {
RequestType struct {
Name string `json:"Name" default:"200ITINS"`
} `json:"RequestType"`
} `json:"IntelliSellTransaction"`
} `json:"TPA_Extensions"`
TravelPreferences struct {
TPAExtensions struct {
DataSources struct {
ATPCO string `json:"ATPCO" default:"Enable"`
LCC string `json:"LCC" default:"Disable"`
NDC string `json:"NDC" default:"Disable"`
} `json:"DataSources"`
NumTrips struct {
} `json:"NumTrips"`
} `json:"TPA_Extensions"`
} `json:"TravelPreferences"`
TravelerInfoSummary struct {
AirTravelerAvail []struct {
PassengerTypeQuantity []struct {
Code string `json:"Code"`
Quantity int `json:"Quantity"`
} `json:"PassengerTypeQuantity"`
} `json:"AirTravelerAvail"`
SeatsRequested []int `json:"SeatsRequested" default:"1"`
} `json:"TravelerInfoSummary"`
Version string `json:"Version" default:"1"`
} `json:"OTA_AirLowFareSearchRQ"`
}
// AddADepartureDate to set the date you leave
func (a *Availabilityrequest) AddADepartureDate() Availabilityrequest {
a.OTAAirLowFareSearchRQ.OriginDestinationInformation[0].DepartureDateTime = "2020-03-21"
return *a
}
//AddOriginDestination to set the ori and dest
func (a *Availabilityrequest) AddOriginDestination(Origin ,Destination string) {
a.OTAAirLowFareSearchRQ.OriginDestinationInformation[0].DestinationLocation.LocationCode = Destination
a.OTAAirLowFareSearchRQ.OriginDestinationInformation[0].OriginLocation.LocationCode = Origin
}
Now I've imported this package into my main one and having issue instatntiating with only one substruct(TPAExtensions)
main.go
package main
import (
"restconsume"
"fmt"
)
func main() {
var a= new(restconsume.Availabilityrequest)
a = Availabilityrequest{
"OTA_AirLowFareSearchRQ":OTAAirLowFareSearchRQ{
"IntelliSellTransaction": IntelliSellTransaction{
"RequestType": RequestType{
"Name": "200ITINS"},
},
},
}
}
error message
undefined: Availabilityrequest
My question is how could I instantiate this kind of complex struct?
The simplest answer is to not try to use struct literal but rather have a variable of the top-level type to be initialized to an appropriate zero value for its type and then explicitly set only those fields which are needed, like this:
var a Availabilityrequest
a.OTAAirLowFareSearchRQ.TPAExtensions.IntelliSellTransaction.RequestType.Name = "200ITINS"
But honestly, judging from your question, it looks like you're JavaScript programmer trying to attack Go without much prior knowledge about that language. This is a path to suffering.
Please be advised to at least start with the Tour of Go and then read any introductory-level book on Go (I would recommend this one).
"Effective Go" is also a must.
I have a meal struct that "appends" another struct, except I want to add another struct "mealComponents".
type mealMain struct {
*model.Meal
Components []mealComponent `json:"components"`
}
type mealComponent struct {
*model.MealComponent
}
Where *model.Meal is as follows
type Meal struct {
ID int64 `json:"id"`
}
What I want is basically for "mealMain" struct to act like "Meal" struct, so that I can assign values and somehow append mealComponent as child (or maybe this is not a good idea? I'm open to suggestions)
However when I do something like this
var meal mealMain
meal.ID = 1
It throws runtime error: invalid memory address or nil pointer dereference at meal.ID assignment.
But if I do it like this:
type mealMain struct {
MealMain *model.Meal `json:"meal_main"`
Components []mealComponent `json:"components"`
}
Then assign it this way:
var meal mealMain
meal.mealMain.ID = 1
It works properly, but I have the return json even deeper like this:
{
"MealModel": {
"id": 1
}
}
What I want is this:
{
"id": 1
}
Note: I want to avoid changing the model.
If you don't want to change the model:
var meal = mealMain{
Meal: &Meal{},
}
meal.ID = 1
The point is that in the following struct *Meal is set to nil if you don't initialize it.
type mealMain struct {
*Meal
Components []mealComponent `json:"components"`
}
I'd probably create a function to never have to worry about the correct initialization ever again:
func newMealMain() mealMain {
return mealMain{
Meal: &Meal{},
}
}
Then your code would be:
var meal = newMealMain()
meal.ID = 1