I'm trying to cascade delete the below structure:
type Action struct {
gorm.Model
Name string
Email string
Halls []Hall `gorm:"foreignKey:ActionID"`
}
type Hall struct {
gorm.Model
Name string
ActionID uint
Stream Stream `gorm:"foreignKey:HallID"`
}
type Stream struct {
ID uint `gorm:"primaryKey"`
HallID uint
Name string
}
db.Select("Halls").Delete(&action) - works fine for selected action and with all related halls.
How can I delete this one and related streams?
Something like:
db.Select("Halls", "Streams").Delete(&action)
db.Select("Streams").Select("Halls").Delete(action)
doesn't work.
Thanks
you can not use delete and select at same time in same query means it not feasible solution to do that
but yeah you can use this reference link
Try Deleting action with where condition and specify HallID
db.Where("hall_id IN ?",HallID).Delete(&action)
and SET HallID to constraint:OnDelete:CASCADE in Stream so when you delete Halls then automatically Streams will be deleted whichever associated with that Halls
I cannot comment on M_x so I'll put this as an answer.
You are allowed to 'Delete' with 'Select' with associations. See https://gorm.io/docs/associations.html#Delete-with-Select
However, I'm also looking for a solution for nested associations where the nested is a slice of a struct.
Related
Let's say I have the following types.
type Contract struct {
Id string `json:"id" gorm:"column:uuid"`
Name string `json:"name" gorm:"column:name"`
Description string `json:"descr" gorm:"column:descr"`
ContractTypeId int `json:"contract_type_id" gorm:"column:contract_type_id"`
}
type ContractModel struct {
Id string `json:"id" gorm:"column:uuid"`
Name string `json:"name" gorm:"column:name"`
Description string `json:"descr" gorm:"column:descr"`
}
I have a SQL query using gorm to scan results into a contract object.
How can I map the values from the contract object into contractModel object?
I tried using the package go-automapper as such:
automapper.Map(contract, ContractModel{})
I want to drop the ContractTypeId.
Can I do this for multiple types in a list?
var contractModels []ContractModel
automapper.Map(contracts, &contractModels)
You can do either:
models := []ContractModel{}
automapper.Map(contracts, &models)
Or call automapper.Map in a loop:
models := make([]ContractModel, len(contracts))
for i := range contracts {
automapper.Map(contracts[i], &models[i])
}
You should be aware that automapper uses reflection behind the scenes and thus is much slower than straight forward non-polymorphic copying like #ThinkGoodly suggests. It's a totally fine solution if performance isn't top priority though.
I'm playing a bit with Gorm while I'm trying to decide which ORM library fit the most for my needs.
Important to mention that I'm currently working with Sqlite.
Following the guide I created two structs:
type Color struct {
gorm.Model
UserID uint
Name string
}
//User struct define a basic user model
type User struct {
gorm.Model
Username string
Email string
FirstName string
LastName string
Password string
CreationDate time.Time
DOB time.Time
IgnoreMe int `gorm:"-"` // Ignore this field
Color Color `gorm:"foreignkey:ColorRefer"`
ColorRefer uint
}
when I'm creating a DB with
func CreateTables() {
user := dm.User{}
color := dm.Color{}
GormDB.CreateTable(&color)
GormDB.CreateTable(&user)
GormDB.Model(&user).AddForeignKey("ColorRefer", "colors(id)", "CASCADE", "CASCADE")
}
or with:
func CreateTables() {
GormDB.AutoMigrate(&dm.User{},&dm.Color{})
}
Sadly it's not working as I would of expect and create the foreign key automatically, but it's works when I do it manually.
My main problem is when I'm trying to query Users
//QueryByStructExample query users table by the struct non-zero (non-default) fields.
func QueryByStructExample(userStruct dm.User) []dm.User {
var results []dm.User
GormDB.Where(userStruct).Find(&results)
return results
}
I created the following function in a try to query users by email with the color property which is my color struct and I tried to play with a lot with the Model,Related and the Association functions, and nothing seems to work and (I'm avoiding to use join by purpose).
The end result is that it query my User but without the color (only with the ID in my colorRefer)
any suggestion?
Do you mean to preload the Color struct? If yes did you try to query it like that
GormDB.Preload('Color').Where(userStruct).Find(&results)
is there a way to automatically remove associations when an object is saved?
something like this:
type Parent struct {
gorm.Model
Name string
Children []*Child
}
type Child struct {
gorm.Model
Name string
ParentID uint
}
func myFunc(db *gorm.DB) {
p := &Parent{Name: "foo", Children:[]*Child{ {Name:"Bar"}, {Name:"Foobar"}}}
db.Save(&p)
p.Children = p.Children[1:]
db.Save(&p) // both children still exist in the database. i'd like the first child to be deleted here
}
`
I've found some tricks with db.Model(&Parent).Association("Children").Clear(), but that just sets the ParentID value to NULL, rather than deleting the record. Is there a simple way of doing this?
Many thanks in advance :)
I think you just simply use the physical batch delete like following code:
db.Unscoped().Where("parent_id = ?", p.ID).Delete(Child{})
Hope this help.
I have a nested struct
type Posts struct {
Id int
CreatedAt time.Time
Data struct {
Title string
UserName string
}
}
I want to create a Data object but var innerData Posts.Data doesn't seem to work. I don't want to create separate Data struct because I'm planning to avoid name collusions by having multiple structs which will have different inner structs named Data.
You can't. Posts.Data isn't the name of a type. The only thing you could do is var innerData struct{ ... }, which I'm sure you don't want to because then you would have repetition and need to make changes in two places. Otherwise, you have to give it a name. That name doesn't have to be Data, it can be PostData or something to make it unique.
I have 2 structs with data like this:
type User struct {
Pics Pic[]
}
type Pic struct {
Id int
UserId int64
}
Although everytime I insert an User, Each of the pics are inserted on their table everytime I find the users, pics are not populated:
var users []User
db.Limit(pagesize).Where("updated_at > ?", date).Find(&users)
Am I doing something wrong?
Your models (the structs) don't really make sense because User have a Pic array indicates a 'one to many' user to pics relationship however your user has no id property itself and there for cannot be related to items on the Pic table.
User should have a property Id which will be it's primary key and UserId is a foreign key on Pic that relates to it. Without the 'relation' between these two tables/entities there's no way you're going to return pics by querying users.
I'm not sure what all you need to do to make your code work since the example is incomplete but the first thing you need is an Id property which you should designate as a Primarykey with gorm annotations. You also should have annotations on the Pic struct saying UserId is a foreign key and Id is it's primary key.
Also, just fyi your array is not embedded. Embedding is a language feature which you're not using, if you embed the property it has no name and it's properties can be accessed directly from an instance of the embedding type.
I had these issues once. Then I used Join function.
See my example that works just fine:
type FileType struct {
Id int
}
type File struct {
Id int
FileType `xorm:"extends"`
}
file := File{Id: id}
has, err := eng.
Join("INNER", "FileType", "FileType.IdFileType = File.IdFileType").
Get(&file)
You probably know by now. You got to think as if you are creating a SQL table with 1-to-many relationship. Here is an example:
type Entry struct {
ID int
Name string
...
ContainerID int
}
type Container struct {
ID int
Tag int
Name string
...
Entries []Entry `gorm:"foreignkey:ContainerID"`
}
The trick is to populate it. I am yet to find how to make it in one try. For every such dependency, you got to run something like:
c := getContainerFromDB(...)
if err := getROConn().Model(c).Related(&c.Entries, "Entries").Error; err != nil {
return errors.Wrap(err, "error getting container field")
}
Try Preload
db.Limit(pagesize).Where("updated_at > ?", date).Preload("Pics").Find(&users)