在Golang中将结构与数据库创建绑定

Question

How to bind data struct with database creation in Golang along with its tags/flags.

For example I have this code:

type User struct {
    ID      int     `sql:"primary_key;AUTO_INCREMENT"`
    Name    string  `sql:"type:varchar(100);unique"`
    Email   string  `sql:"type:varchar(100);unique"`
    Address string  `sql:"type:varchar(100)"`
}

When creating the database which should be based on this struct, I instead manually create it like this:

func (db *DB) CreateUserTable() (sql.Result, error) {

    statement := "CREATE TABLE IF NOT EXISTS %s (%s int, %s varchar, %s varchar, %s varchar)"
    return db.Exec(
        fmt.Sprintf(statement,
            "user",
            "id",
            "name",
            "email",
            "address",
        ),
    )
}

How to bind the struct and its tags(primary key, NULL, etc) in database creation?. Is there best practice for it without using ORM libraries(gorm,etc)?

Answer 1

You can use reflect to examine the struct and use it to construct your database query.

For example:

If you want to read struct's name to use it as table name:

tableName := reflect.TypeOf(your-struct).Name()

If you want to read struct's properties, loop and read it by using:

val := reflect.ValueOf(your-struct)
for i:=0; i < val.NumField(); i++ {
    field := val.Type().Field(i)
    tag := field.Tag

    fieldType := field.Type // get struct's variable type
    fieldName := field.Name //get struct variable's name
    fieldByTag1 := tag.Get("your-tag") // get struct tag's name 
    fieldByTag2 := tag.Get("your-another-tag") // get another struct tag's name(if you have more)
}

Note that struct's tags are the one inside back tick -> `

That's all you need to get from a struct. You should explore more in the documentation.