如何在Golang中将数组文档设置为Redis？

Question

I have a problemwhen insert document in to redis.

I have a struct of data in Go:

type ArticleCovers struct {
    ID             int
    Covers         ArticleCovers
    ArticleTypeID  int
    Address        Address     `gorm:"ForeignKey:AddressID"`
}

I want to add a data like this into Redis:

[ID:1 Cover:[http://chuabuuminh.vn/UserImages/2012/12/10/1/chinh_dien_jpg.jpg] ArticleTypeID:1 Address:map[Street: City:<nil> District:<nil> DistrictID:0 ID:0 Slug: Lat:0 Long:0 Ward:<nil> WardID:0 CityID:0]] 

But when I run Redis.HMSet("test", structs.Map(ret)) it return the error: redis: can't marshal postgresql.ArticleCovers (consider implementing encoding.BinaryMarshaler).

Who can help me fix my problem, thks you so much!

Answer 1

Like the error message says, you need to implement the BinaryMarshaler interface for your ArticleCovers type:

type ArticleCovers struct {
    ID             int
    Covers         ArticleCovers
    ArticleTypeID  int
    Address        Address     `gorm:"ForeignKey:AddressID"`
}

func (ac ArticleCovers) MarshalBinary() ([]byte, error) {
    return []byte(fmt.Sprintf("%v-%v", ac.ID, ac.ArticleTypeID)), nil
}

Note that this only adds the ID and ArticleTypeID fields. I don't know what the ArticleCovers and Address types look like, but often you want to call the same methods on that:

func (ac ArticleCovers) MarshalBinary() ([]byte, error) {
    covers, err := ac.Covers.MarshalBinary()
    if err != nil {
        return nil, err
    }
    address, err := ac.Address.MarshalBinary()
    if err != nil {
        return nil, err
    }

    return []byte(fmt.Sprintf("%v-%v-%v-%v",
        ac.ID, ac.ArticleTypeID, covers, address)
}

I don't know if this format makes sense for your data. You may want to use a defined encoding format such as json.

You will probably also want to implement the BinaryUnmarshaler interface. Doing that is left as an exercise ;-)