Similar to this question, but in the case of one-to-many: Associations not working with test entries
I have two models User and E-Mails in GORM defined: File user.go
type User struct {
gorm.Model
Identity string `json:"identity"`
Password string `json:"password"`
Emails []Email
}
type Email struct {
gorm.Model
UserID uint
Text string `json:"text"`
Sender string `json:"sender"`
}
According to the documentation this should work with a test entry:
userRec := &user.User{ Identity: "John Wayne", Password: "mysecretpassword", Emails: []user.Email{user.Email{Text: "My Text", Sender: "julia#world.me"}, user.Email{Text: "My Text", Sender: "julia#world.me"}}}
However, the Email entries do not get associated with the User object.
Is it normal that the User object does not have entries to which Email objects it is referring to (as opposed to the "refer to" case)?
How can I query a User with all the corresponding Email objects?
All Emails are available via
var emails[] Email
db.Where("user_id = ?", id).Find(&emails)
You need to Preload (eager load) the emails table, by referring to its column name:
user := &User{}
db.Preload("Emails").First(user)
If you are using one-to-one relations, you can also do it automatically by calling:
db.Preload(clause.Associations).Find(user)
Note: This will not work for one-to-many relations.
There is some other functionality supported, such as nested Preloading, and combining joins and preloads together (for the purpose of filtering or ordering on sub-tables) defined in the GORM Docs
Related
I am new to ORM (and GORM) so apologies if this is an obvious question, but it does not seem to be covered by the documentation.
I will be using the examples from the documentation as a base to my questions
Question 1: Belongs To
// `User` belongs to `Company`, `CompanyID` is the foreign key
type User struct {
gorm.Model
Name string
CompanyID int
Company Company
}
type Company struct {
ID int
Name string
}
A User belongs to one Company only → this is handled by the code
above
A Company has many User → is this implied by the code
above? Or should I add somehow a relation O2M in Company?
Question 2: Has Many
// User has many CreditCards, UserID is the foreign key
type User struct {
gorm.Model
CreditCards []CreditCard
}
type CreditCard struct {
gorm.Model
Number string
UserID uint
}
A User has 1+ CreditCard→ this is handled by the code
A CreditCard can belong to several users (say, a shared family CC) → is it implied? (if not: how to set up the O2M relationship).
Or is it, instead, a case where a CreditCard is explicitly configured to belong to only one user?
Q1: Based on how you defined your structs, you don't need an explicit O2M relationship in the Company struct, but when loading Company details, if you want to load all users that are assigned to that specific company, you need to add that field as well. It will need an additional function call like Preload or Joins, but you shouldn't need an explicit definition of this relationship.
type Company struct {
ID int
Name string
Users []User
}
Q2: The way the relationship is defined now, it is configured so that a CreditCard belongs to only one user. If you want a many2many relationship, you need to specify the relation table. There is more documentation on it here, but it should look something like this:
type User struct {
gorm.Model
CreditCards []CreditCard `gorm:"many2many:users_creditcards"`
}
type CreditCard struct {
gorm.Model
Number string
}
I have managed to use the local context to set database query results using a custom middleware. I am trying to see how I can authenticate a user then pull their details from the database and inject it to the context. This has been done.
The local data on the final method on the route is actually an interface and I would like to extract fields from the data I set from the previous auth middleware. How can I work with this interface type to some form like a struct or json so that I can get the fields and values for doing some logic?
user := c.Locals("user")
fmt.Println("checking for locals",user)
From above user is of struct user
{
Name string `json:"name"`
Emain string `json:"email"`
ID string `json:"id"`
Password string `json:"password"`
}
How can I get the name and email ?
So after digging into the fiber docs and reading about interfaces and especially empty interfaces I think I have a solution but stand to be corrected
I saw one can cast an interface to a concrete type. In my case I would take the c.Locals("user") of type var user interface{}
then cast it to a struct passing the pointer to the user model as follows
user := c.Locals("user")
details, ok :=user.(*models.User)
fmt.Println("checking for locals -----------",details.Name)
I want to create a model User and Social where the User model has many Socials. Ideally a Social type would also have has one relation to simpilify querying from either side. Here is a code sample:
database type is MySQL 8.0
type base struct {
ID string `json:"id" gorm:"type:char(36);primaryKey;"`
Created time.Time `json:"created" gorm:"autoCreateTime"`
Updated time.Time `json:"updated" gorm:"autoUpdateTime"`
}
type User struct {
base
Friends []*User `json:"friends" gorm:"many2many:friends"`
Socials []*Social `json:"socials"`
}
type Social struct {
base
Provider string `json:"provider" gorm:"type:varchar(32);index"`
Identifier string `json:"identifier" gorm:"type:varchar(32);index"`
User *User `json:"user" gorm:"foreignKey:ID"`
Token string `json:"token"`
Link string `json:"link" gorm:"type:varchar(128)"`
}
Im getting the following error when using db.AutoMigrate(&User{}, &Social{}):
model.Social's field User, need to define a valid foreign key for relations or it need to implement the Valuer/Scanner interface
runtime error: invalid memory address or nil pointer dereference
I have tried:
adding gorm:"foreignKey:ID" to User.Socials tags
not using pointers (eg in User struct Socials []Social instead of Socials []*Social)
but the issue remains
According to documentation (https://gorm.io/docs/has_many.html#Has-Many),
you need to use objects, not references
type User struct {
base
Friends []User `json:"friends" gorm:"many2many:friends"`
Socials []Social `json:"socials"`
}
no * here
Also you can add UserID field to Social
type Social struct {
base
UserID string
Provider string `json:"provider" gorm:"type:varchar(32);index"`
Identifier string `json:"identifier" gorm:"type:varchar(32);index"`
User *User `json:"user" gorm:"foreignKey:ID"`
Token string `json:"token"`
Link string `json:"link" gorm:"type:varchar(128)"`
}
and add
type User struct {
base
FriendOf string `gorm:""`
Friends []*User `json:"friends" gorm:"many2many:friends,foreignKey:FriendOf"`
Socials []*Social `json:"socials"`
}
Issue was here:
type base struct {
...
}
type User {
base
...
}
type Social {
base
...
}
Since I thought base would just be package local definition I messed up the capitalization and had a private primary key.
Another issue was touched on by #vodolaz095, but (imo) not sufficiently clarified for any new go-gorm user.
It does not seem to be possible to use a has one relation like User User be the foreign key for a has many relation like Socials []Social gorm:"foreignKey:User". It is required to be split up as #vodolaz095 displayed in his 2nd code block
I have the following query:
db.Where("user_id = ?", tmpUser.ID).Find(&subscriptions)
subscriptions is a slice of the subscription object.
The problem is, it will output all subscriptions include the related objects (like the user object).
How can I query the database and get back only subscription records without the related (belongs to and has many) objects?
You can use the auto_preload setting:
db.Set("gorm:auto_preload", false).Where("user_id = ?", tmpUser.ID).Find(&subscriptions)
Or you can use the PRELOAD struct tag:
type Subscription struct {
ID uint
User User `gorm:"PRELOAD:false"`
UserID uint
}
https://gorm.io/docs/preload.html#Auto-Preloading
db.Find(&subscriptions). if you want count append .Count(&count) object
Using Jinzhu's GORM Package which is fantastic btw, I currently have this struct:
type User struct {
gorm.Model
// The Users username
Username string `gorm:"size:255;unique;not null"`
// The Users email address
Email string `gorm:"size:255;unique;not null"`
// The Users hashed password
Password string `gorm:"size:255;not null"`
// The Users password confirmation (only for forms)
PasswordC string `gorm:"-"`
// The Users FULL NAME (e.g. Burt Reynolds)
Fullname string `gorm:"size:255; not null"`
// The Users Karma level
Karma int
// Is the user banned?
Banned bool
}
But I also use Gorilla's Schema package so any form values populate the struct, but I don't want the PasswordC to be saved into the database because it will be plain text as the normal Password field gets bcrypt'd so any information on how to make GORM not save the PasswordC field.
The docs say gorm:"-", but the code indicates sql:"-" is the correct syntax.
My testing verifies this.
This is no longer correct. The code has been fixed, still use gorm:"-".