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README
¶
null int and string values
This module provides (yet another) alternative in dealing with integers and strings which may be null in your JSON or database. There are various different approaches to this, namely the built in golang SQL types and the guregu null module which adds in JSON support. These are fine approaches but both suffer from you having to deal with a struct type for your ids instead of a more natural int64 or string. That is fine in some cases but I prefer to use more primitive types as assignment is more straightforward, simple equality works, etc.
Sadly this requires a bit of boilerplate, so this package tries to make that a bit easier, proving helper methods for marshalling to/from json and reading / scanning from a database value. Due to the Golang type system, using these requires some boilerplate, but I find it nicer to have a bit more code for my ID types and less awkward code around the usage of ids rather than vice versa.
To define your own ID type which is nullable when written:
import "github.com/nyaruka/null"
type CustomID null.Int
const NullCustomID = CustomID(0)
// MarshalJSON marshals into JSON. 0 values will become null
func (i CustomID) MarshalJSON() ([]byte, error) {
return null.Int(i).MarshalJSON()
}
// UnmarshalJSON unmarshals from JSON. null values become 0
func (i *CustomID) UnmarshalJSON(b []byte) error {
return null.UnmarshalInt(b, (*null.Int)(i))
}
// Value returns the db value, null is returned for 0
func (i CustomID) Value() (driver.Value, error) {
return null.Int(i).Value()
}
// Scan scans from the db value. null values become 0
func (i *CustomID) Scan(value interface{}) error {
return null.ScanInt(value, (*null.Int)(i))
}
The process is essentially the same for nullable strings:
import "github.com/nyaruka/null"
type CustomString null.String
type NullCustomString = CustomString("")
// MarshalJSON marshals into JSON. "" values will become null
func (s CustomString) MarshalJSON() ([]byte, error) {
return null.String(s).MarshalJSON()
}
// UnmarshalJSON unmarshals from JSON. null values become ""
func (s *CustomString) UnmarshalJSON(b []byte) error {
return null.UnmarshalString(b, (*null.String)(s))
}
// Value returns the db value, null is returned for ""
func (s CustomString) Value() (driver.Value, error) {
return null.String(s).Value()
}
// Scan scans from the db value. null values become ""
func (s *CustomString) Scan(value interface{}) error {
return null.ScanString(value, (*null.String)(s))
}
If you don't care about type safety within your types, you can use a go alias which simplifies things. This is more useful for "stringy" things than it is for ids where you likely want to enforce type:
import "github.com/nyaruka/null"
// Note you lose type safety with aliases. FooID can be assigned to BarID and vice versa!
type FooID = null.Int
type BarID = null.Int
// Same here, any null.String can be assigned to CustomString
type CustomString = null.String
Documentation
¶
Index ¶
- Constants
- func ScanInt(value interface{}, v *Int) error
- func ScanString(value interface{}, v *String) error
- func UnmarshalInt(b []byte, v *Int) error
- func UnmarshalString(b []byte, v *String) error
- type Int
- type JSON
- type Map
- func (m *Map) Get(key string, def interface{}) interface{}
- func (m *Map) GetString(key string, def string) string
- func (m *Map) Map() map[string]interface{}
- func (m Map) MarshalJSON() ([]byte, error)
- func (m *Map) Scan(src interface{}) error
- func (m *Map) UnmarshalJSON(data []byte) error
- func (m Map) Value() (driver.Value, error)
- type String
Constants ¶
const NullInt = Int(0)
NullInt is our constant for an Int value that will be written as null
const NullString = String("")
NullString is our constant for an String value that will be written as null
Variables ¶
This section is empty.
Functions ¶
func ScanInt ¶
ScanInt is a utility method that can be used to scan a db value and return an Int and error In the case of an error, null or "" values, NullInt is returned
func ScanString ¶
ScanString is a utility method that can be used to scan a db value and return a String and error In the case of an error, null or "" values, NullString is returned
func UnmarshalInt ¶
UnmarshalInt is a utility method that can be used to unmarshal a json value to an Int and error In the case of an error, null or "" values, NullInt is returned
func UnmarshalString ¶
UnmarshalString is a utility method that can be used to unmarshal a json value to a String and error In the case of an error, null or "" values, NullString is returned
Types ¶
type Int ¶
type Int int64
Int is an int that will write as null when it is zero both to databases and json null values when unmashalled or scanned from a DB will result in a 0 value
func (Int) MarshalJSON ¶
MarshalJSON marshals our int to JSON. 0 values will be marshalled as null
func (*Int) UnmarshalJSON ¶
UnmarshalJSON unmarshals our JSON to int. null values will be marshalled to 0
type JSON ¶ added in v1.2.0
type JSON json.RawMessage
JSON is a json.RawMessage that will marshall as null when empty or nil. null and {} values when unmashalled or scanned from a DB will result in a nil value
func (JSON) MarshalJSON ¶ added in v1.2.0
MarshalJSON encodes our JSON to JSON or null
func (*JSON) Scan ¶ added in v1.2.0
Scan implements the Scanner interface for decoding from a database
func (*JSON) UnmarshalJSON ¶ added in v1.2.0
UnmarshalJSON sets our JSON from the passed in JSON
type Map ¶ added in v1.1.1
type Map struct {
// contains filtered or unexported fields
}
Map is a one level deep dictionary that is represented as JSON text in the database. Empty maps will be written as null to the database and to JSON.
func (*Map) GetString ¶ added in v1.1.1
GetString returns the string value with the passed in key, or def if not found or of wrong type
func (Map) MarshalJSON ¶ added in v1.1.1
MarshalJSON encodes our map to JSON
func (*Map) Scan ¶ added in v1.1.1
Scan implements the Scanner interface for decoding from a database
func (*Map) UnmarshalJSON ¶ added in v1.1.1
UnmarshalJSON sets our map from the passed in JSON
type String ¶
type String string
String is string that will write as null when it is "" both to databases and json null values when unmashalled or scanned from a DB will result in a "" value
func (String) MarshalJSON ¶
MarshalJSON marshals our string to JSON. "" values will be marshalled as null
func (*String) UnmarshalJSON ¶
UnmarshalJSON unmarshals our json to a string. null values will be marshalled to ""
Source Files