I am having a json as
{
"fields": ["time","id","status","customerId","additionalDetail"],
"pageInfo": {"start": 0, "rows": 1000}
}
I wanted to Marshal my structure to above json and create the structure as below -
type RBody struct {
Fields []string `json:"fields"`
PageInfo struct {
Start int `json:"start"`
Rows int `json:"start"`
} `json:"pageInfo"`
}
I am having trouble in initializing the above structure. I am not sure how to initialize the anonymous struct in below fashion :
bd := RBody {
Fields : []string{"time","id","status","customerId","additionalDetail"},
PageInfo : ???
}
I worked around this by creating a separate structure for page info and attaching that with parent struct. However there's got to be some way to perform the initialisation of the anonymous nested struct, in the same way I did with Fields (string slice) above. Can anyone redirect me to some guide to do that ?
This works, but it is ugly:
bd := RBody { Fields : []string{"time","id","status","customerId","additionalDetail"},
PageInfo : struct {Start int `json:"start"`
Rows int `json:"rows"`} {Start:1,Rows:2}}
I suggest you either name the anonymous struct, or initialize Fields in the declaration, and PageInfo using assignments later.
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())
}
model.go:
type First struct {
ID int `json:"id" gorm:"column:id;primary_key"`
Status string `json:"status" gorm:"column:status"`
SecondID int `json:"second_id" gorm:"column:second_id"`
SecondData Second `json:"second_data" gorm:"foreignKey:SecondID;references:ID"`
}
type Second struct {
ID int `json:"id" gorm:"column:second_id;primary_key"`
Status string `json:"status" gorm:"column:status"`
Description string `json:"description" gorm:"column:description"`
}
var res []model.First
db.Raw("first.*, second.* FROM first LEFT JOIN second ON first.second_id = second.second_id")
db.Preload("SecondData").Find(&res).Error
Output:
{
"id": 1,
"status": "A",
"second_id": 1
"second_data": {
"id": 1
"status": "B",
"description": "blablabla"
}
}
I don't really know how db.Preload() works. Why i should use db.Preload() to get "SecondData" every time i need do nested struct ? Are it's possible only use db.Row() or db.Table().Joins().Where().Find(), i mean's without db.Preload()?
If you want SecondData loaded every time when the First struct is loaded without using Preload, you might consider using hooks.
It might look something like this:
func (f *First) AfterFind(tx *gorm.DB) error {
return tx.First(&f.SecondData, f.SecondID).Error
}
So, when you load the First data, the AfterFind hook should be triggered.
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.
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
Please see this playground: https://play.golang.org/p/FOMWqhjdneg
As you can see I have a XML response which I want to unmarshal into a Product struct. The XML has an "assetBlock" which contains nested nodes and extract data to Product struct. Any help would be appreciated
You need to make a struct for AssetBlock and all of the types below it, I've done it up to group to show you what I mean:
https://play.golang.org/p/vj_CkneHuLd
type Product struct {
GlobalID string `xml:"globalId"`
Title string `xml:"title"`
ChunkID int `xml:"gpcChunkId"`
AssetBlock assetBlock `xml:"assetBlock"`
}
type assetBlock struct {
Images images `xml:"images"`
}
type images struct {
GroupList groupList `xml:"groupList"`
}
type groupList struct {
Groups []group `xml:"group"`
}
type group struct {
Usage string `xml:"usage"`
Size string `xml:"size"`
}