如何用go检查空字符串类型？

DB:

column: name
value: NULL

Get the record from DB with gorm, then

var name string
if name != nil {
  //
}

Got error:

invalid operation: name != nil (mismatched types string and nil)

Yes, nil is using for int type in go, but this case, the value in DB is NULL but not "", so it's necessary to check null, how to do?

You can also use a pointer to string to map NULL values from the database, but this will create cases where you cannot give values without creating a variable first.

var name *string
if name != nil {
  //
}

// but
name = "will not work"

Or you could use the github.com/go-sql-driver/mysql(or whatever driver you are using) and database/sql package implementations. You can define your own types based on those if you want to add functionality:

// NullInt64 is an alias for sql.NullInt64 data type
type NullInt64 sql.NullInt64
// NullBool is an alias for sql.NullBool data type
type NullBool sql.NullBool
// NullFloat64 is an alias for sql.NullFloat64 data type
type NullFloat64 sql.NullFloat64
// NullString is an alias for sql.NullString data type
type NullString sql.NullString
// NullTime is an alias for mysql.NullTime data type
type NullTime mysql.NullTime

You should pay your attention on sql types: https://golang.org/pkg/database/sql/#NullString

Just use variable with this type in your select statement:

var yourstr sql.NullString
db.Select("Select your string", &yourstr)

Then you could check if it is valid and if it is not you could assign any value you want:

if !yourstr.Valid{
  yourstr.String = ""
}

In gorm also is a function to select NullString:

yourstr := dbmap.SelectNullStr("Select your string")