Using a pointer reference to a foreign-key related model in Gorm (golang)-CodePudding

Suppose you have database models as follows:

package storage

type Country struct {
    ID   string `json:"id" gorm:"type:uuid"`
    Name string `json:"name"`
    Code string `json:"code"`
}

type City struct {
    ID           string   `json:"id" gorm:"type:uuid"`
    Name         string   `json:"name"`
    Code         *string  `json:"code"`
    CountryId    string   `json:"country_id"`
    Country      *Country `json:"country" gorm:"references:ID"`
    IATA         *string  `json:"iata"`
    Latitude     *string  `json:"latitude"`
    Longitude    *string  `json:"longitude"`
}

The city should have a pointer to a Country model to make it easier to understand whether Country has been joined (in sql) or not (e.g. if city.Country == nil {panic("for whatever reason")} )

The problem appears when I try to get the list of all cities:

package example

var cities []storage.City 
tx.Joins("Country").Find(&cities)

Here, all the cities have been fetched from DB nicely, but the countries became the same in all the cities.

EXPECTED OUTPUT
[
{
 ID:51e415ab-4301-4268-9345-deed6b1d72f6 
 Name:Bergen 
 Code:0xc0004d6ec0 
 CountryId:0bd3890c-b6b7-4b27-8071-55c8f64562bb 
 Country:{
    ID:0bd3890c-b6b7-4b27-8071-55c8f64562bb 
    Name:Norwegen 
    Code:NO
   } 
 SkyScannerId:0xc0004d6ee0 
 IATA:0xc0004d6ef0 
 Latitude:0xc0004d6f00 
 Longitude:0xc0004d6f10
},
 
{
 ID:2468c7f0-0275-4bff-8b7e-4e87bfa63604 
 Name:Banská Bystrica 
 Code:0xc0004d6bc0 
 CountryId:00ba76d3-9591-4d45-a39d-f554375d790f 
 Country: {
    ID:00ba76d3-9591-4d45-a39d-f554375d790f 
    Name:Slovakei 
    Code:SK
   } 
 SkyScannerId:<nil> 
 IATA:<nil> 
 Latitude:0xc0004d6c00 
 Longitude:0xc0004d6c10
}, 

{
 ID:75501988-3c80-4ef9-8081-73d20cbcc29b 
 Name:Prag 
 Code:0xc0004d6a60 
 CountryId:f4e819b2-5c1a-43f9-bfa1-fe56b6ee173e 
 Country:{
    ID:f4e819b2-5c1a-43f9-bfa1-fe56b6ee173e 
    Name:Tschechien 
    Code:CZ
  } 
 SkyScannerId:0xc0004d6a90 
 IATA:0xc0004d6aa0 
 Latitude:0xc0004d6ac0 
 Longitude:0xc0004d6ad0
}
] 



ACTUAL OUTPUT:

[
{
 ID:51e415ab-4301-4268-9345-deed6b1d72f6 
 Name:Bergen 
 Code:0xc0004d6ec0 
 CountryId:0bd3890c-b6b7-4b27-8071-55c8f64562bb 
 Country:{
    ID:f4e819b2-5c1a-43f9-bfa1-fe56b6ee173e 
    Name:Tschechien 
    Code:CZ
  }
 SkyScannerId:0xc0004d6ee0 
 IATA:0xc0004d6ef0 
 Latitude:0xc0004d6f00 
 Longitude:0xc0004d6f10
},
 
{
 ID:2468c7f0-0275-4bff-8b7e-4e87bfa63604 
 Name:Banská Bystrica 
 Code:0xc0004d6bc0 
 CountryId:00ba76d3-9591-4d45-a39d-f554375d790f 
 Country:{
    ID:f4e819b2-5c1a-43f9-bfa1-fe56b6ee173e 
    Name:Tschechien 
    Code:CZ
  }
 SkyScannerId:<nil> 
 IATA:<nil> 
 Latitude:0xc0004d6c00 
 Longitude:0xc0004d6c10
}, 

{
 ID:75501988-3c80-4ef9-8081-73d20cbcc29b 
 Name:Prag 
 Code:0xc0004d6a60 
 CountryId:f4e819b2-5c1a-43f9-bfa1-fe56b6ee173e 
 Country:{
    ID:f4e819b2-5c1a-43f9-bfa1-fe56b6ee173e 
    Name:Tschechien 
    Code:CZ
  } 
 SkyScannerId:0xc0004d6a90 
 IATA:0xc0004d6aa0 
 Latitude:0xc0004d6ac0 
 Longitude:0xc0004d6ad0
}
]

Please pay attention to Country field of the outputs. In the ACTUAL OUTPUT all the cities have the same country. I think this has something to do with the pointer. I got EXPECTED OUTPUT when I removed the pointer from Country (so *Country became Country without *). But I would like to get the same output with the pointer (*Country). Also, please do not pay attention to the values printed out in other fields. My main focus is the Country field.

Any ideas how to fix it ?

P.S. I know that i can survive without using the pointers too in the Country field, but I just want to know if there are any possibilities to do that.

CodePudding user response：

Try to put countryId as a pointer too.

Like this

 CountryId    *string   `json:"country_id"`

Actually I tried to replicate the error with you code example, but it's working well.

CodePudding user response：

I have noticed that this is the behavior with gorm-v1.23.6. Switching back to gorm-v1.23.5 solved the problem.