如何使用gorm在postgres SQL数据库中存储一个点

Question

我正在尝试在 Go 服务器上使用 GORM 在 SQL 数据库中存储 Point 变量，我尝试到处寻找，但还没有看到让我满意的答案

Answer 1

For any type that's not supported by the standard library's database/sql package, nor by a 3rd party package that depends on database/sql , like gorm does, you can implement the Valuer and Scanner interfaces to add custom support for the type.

To be able to correctly implement those two interfaces you need to first find out what the target database expects as input and what it returns as output for that type. In the case of PostgreSQL and the Point type the syntax is (x,y) .

So what you can do is the following:

1. Declare the type.

type Point struct {
    X, Y float64
}

2. Implement the Valuer interface.

func (p Point) Value() (driver.Value, error) {
    out := []byte{'('}
    out = strconv.AppendFloat(out, p.X, 'f', -1, 64)
    out = append(out, ',')
    out = strconv.AppendFloat(out, p.Y, 'f', -1, 64)
    out = append(out, ')')
    return out, nil
}

3. Implement the Scanner interface.

func (p *Point) Scan(src interface{}) (err error) {
    var data []byte
    switch src := src.(type) {
    case []byte:
        data = src
    case string:
        data = []byte(src)
    case nil:
        return nil
    default:
        return errors.New("(*Point).Scan: unsupported data type")
    }

    if len(data) == 0 {
        return nil
    }

    data = data[1 : len(data)-1] // drop the surrounding parentheses
    for i := 0; i < len(data); i++ {
        if data[i] == ',' {
            if p.X, err = strconv.ParseFloat(string(data[:i]), 64); err != nil {
                return err
            }
            if p.Y, err := strconv.ParseFloat(string(data[i+1:]), 64); err != nil {
                return err
            }
            break
        }
    }
    return nil
}