How can I change the fields of a struct's json marshal? - go

Question

tl;dr
How can I dynamize the JSON fields of a struct?
I am using gorm as the ORM. I have my model definition as a struct:
type UserAccessToken struct {
Id uint `gorm:"primaryKey" json:"-"`
CreatedAt time.Time `json:"createdAt"`
DeletedAt gorm.DeletedAt `json:"deletedAt"`
User User `gorm:"constraint:OnDelete:CASCADE" json:"-"`
UserId uint `gorm:"not null" json:"-"`
IpAddress string `gorm:"not null" json:"ipAddress"`
Token string `gorm:"not null" json:"token"`
}
I have multiple endpoints and I want to use different fields of the struct serialized on each endpoint.
For example, on POST /user-access-tokens/ user will be basic authenticated and a new access token will be created and returned on the response. However, on GET /user-access-tokens/ list API endpoint, the response will be a list of the UserAccessTokens, but the Token won't be on the response. And I am planning to create another endpoint only to be used by the administration interface, and all fields will be available there.
There are two I can think of:
Creating a different struct and reading from the database into this struct.
Adding a method like Map(scenario string) to the model struct which will create a map of the struct according to scenario, but in this case, I also need to add function to handle multiple instances of the struct.
What is the recommended way for this?

Answer 1

You can use another struct:
type UserAccessstruct {
Id uint `gorm:"primaryKey" json:"-"`
CreatedAt time.Time `json:"createdAt"`
DeletedAt gorm.DeletedAt `json:"deletedAt"`
User User `gorm:"constraint:OnDelete:CASCADE" json:"-"`
UserId uint `gorm:"not null" json:"-"`
IpAddress string `gorm:"not null" json:"ipAddress"`
}
type UserAccessToken {
UserAccessstruct
Token string `gorm:"not null" json:"token"`
}
func Get() {
var userAccess UserAccessToken
db.Select(selectQuery).First(&userAccess)
return userAccess // Full return
return userAccess.UserAccessstruct // Inner struct without token
}