Gorm Multiple same-type belongs-to fields not working (?)

Multiple same-type belongs-to fields not working (?)

I'm implementing a database architecture which has 1 one-to-many relation and the 'many' tables implement a belongs-to. The architecture looks like this:

type Pair struct {
    Id              uint64  `json:"id" gorm:"primaryKey;autoIncrement"`
    PairRefer uint64  `json:"refer"`
}

type PairCouple struct {
    Id              uint64  `json:"id" gorm:"primaryKey;autoIncrement"`
    PairCoupleRefer uint64  `json:"refer"`
    BuyPair         Pair    `json:"buy_pair" gorm:"foreignKey:PairRefer"` // gorm:"embedded;column:buy_pair"
    SellPair        Pair    `json:"sell_pair" gorm:"foreignKey:PairRefer"`
}

type Coin struct {
    Id             uint64       `json:"id" gorm:"primaryKey;autoIncrement"`
    ArbitragePairs []PairCouple `json:"pair_couples" gorm:"foreignKey:PairCoupleRefer;references:Id"`
}

In my code I retrieve all 'Coin' records and iterate them to access all data, PairCouple one-to-many works just fine, but then when i access the BuyPair/SellPair the fields are EMPTY

I honestly don't think its an issue related to the associations but rather to the preloading, i honestly have no clue at this point... this is how i retrieve the records: tx = dbCtx.Statement.DB.Preload("BuyPair").Preload("SellPair").Preload("ArbitragePairs").Find(&coins) but this invokes an error 'BuyPair' unsupported relations for schema Coin

Comment From: black-06

Try this:

err := db.
    Preload("ArbitragePairs.BuyPair").
    Preload("ArbitragePairs.SellPair").
    Preload("ArbitragePairs").
    Find(&coins)

But gorm doesn't known how to preload when foreign keys are the same. May be you should use Hasone relatioin

type Pair struct {
    Id   uint64 `json:"id" gorm:"primaryKey;autoIncrement"`
    Name string
}

type PairCouple struct {
    Id              uint64 `json:"id" gorm:"primaryKey;autoIncrement"`
    PairCoupleRefer uint64 `json:"refer"`
    BuyPair         Pair   `json:"buy_pair"` // gorm:"embedded;column:buy_pair"
    BuyPairID       uint64
    SellPair        Pair `json:"sell_pair"`
    SellPairID      uint64
    Name            string
}

type Coin struct {
    Id             uint64       `json:"id" gorm:"primaryKey;autoIncrement"`
    ArbitragePairs []PairCouple `json:"pair_couples" gorm:"foreignKey:PairCoupleRefer;references:Id"`
    Name           string
}

Comment From: Duality1k

Try this:

go err := db. Preload("ArbitragePairs.BuyPair"). Preload("ArbitragePairs.SellPair"). Preload("ArbitragePairs"). Find(&coins)

But gorm doesn't known how to preload when foreign keys are the same. May be you should use Hasone relatioin

``go type Pair struct { Id uint64json:"id" gorm:"primaryKey;autoIncrement"` Name string }

type PairCouple struct { Id uint64 json:"id" gorm:"primaryKey;autoIncrement" PairCoupleRefer uint64 json:"refer" BuyPair Pair json:"buy_pair" // gorm:"embedded;column:buy_pair" BuyPairID uint64 SellPair Pair json:"sell_pair" SellPairID uint64 Name string }

type Coin struct { Id uint64 json:"id" gorm:"primaryKey;autoIncrement" ArbitragePairs []PairCouple json:"pair_couples" gorm:"foreignKey:PairCoupleRefer;references:Id" Name string } ```

Hey, thanks for the reply. I've tried using SellPairID and BuyPairID as a FK too, but no luck. Altought your preloading + separate fk's seems to work fine. Thanks alot :)