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119 lines
2.9 KiB
119 lines
2.9 KiB
// Package null contains SQL types that consider zero input and null input as separate values,
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// with convenient support for JSON and text marshaling.
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// Types in this package will always encode to their null value if null.
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// Use the zero subpackage if you want zero values and null to be treated the same.
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package null
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import (
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"database/sql"
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"encoding/json"
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"fmt"
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"reflect"
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)
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// String is a nullable string. It supports SQL and JSON serialization.
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// It will marshal to null if null. Blank string input will be considered null.
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type String struct {
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sql.NullString
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}
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// StringFrom creates a new String that will never be blank.
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func StringFrom(s string) String {
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return NewString(s, true)
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}
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// StringFromPtr creates a new String that be null if s is nil.
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func StringFromPtr(s *string) String {
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if s == nil {
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return NewString("", false)
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}
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return NewString(*s, true)
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}
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// ValueOrZero returns the inner value if valid, otherwise zero.
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func (s String) ValueOrZero() string {
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if !s.Valid {
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return ""
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}
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return s.String
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}
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// NewString creates a new String
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func NewString(s string, valid bool) String {
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return String{
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NullString: sql.NullString{
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String: s,
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Valid: valid,
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},
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}
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}
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// UnmarshalJSON implements json.Unmarshaler.
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// It supports string and null input. Blank string input does not produce a null String.
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// It also supports unmarshalling a sql.NullString.
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func (s *String) UnmarshalJSON(data []byte) error {
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var err error
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var v interface{}
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if err = json.Unmarshal(data, &v); err != nil {
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return err
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}
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switch x := v.(type) {
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case string:
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s.String = x
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case map[string]interface{}:
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err = json.Unmarshal(data, &s.NullString)
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case nil:
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s.Valid = false
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return nil
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default:
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err = fmt.Errorf("json: cannot unmarshal %v into Go value of type null.String", reflect.TypeOf(v).Name())
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}
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s.Valid = err == nil
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return err
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}
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// MarshalJSON implements json.Marshaler.
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// It will encode null if this String is null.
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func (s String) MarshalJSON() ([]byte, error) {
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if !s.Valid {
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return []byte("null"), nil
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}
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return json.Marshal(s.String)
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}
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// MarshalText implements encoding.TextMarshaler.
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// It will encode a blank string when this String is null.
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func (s String) MarshalText() ([]byte, error) {
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if !s.Valid {
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return []byte{}, nil
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}
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return []byte(s.String), nil
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}
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// UnmarshalText implements encoding.TextUnmarshaler.
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// It will unmarshal to a null String if the input is a blank string.
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func (s *String) UnmarshalText(text []byte) error {
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s.String = string(text)
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s.Valid = s.String != ""
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return nil
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}
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// SetValid changes this String's value and also sets it to be non-null.
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func (s *String) SetValid(v string) {
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s.String = v
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s.Valid = true
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}
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// Ptr returns a pointer to this String's value, or a nil pointer if this String is null.
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func (s String) Ptr() *string {
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if !s.Valid {
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return nil
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}
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return &s.String
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}
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// IsZero returns true for null strings, for potential future omitempty support.
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func (s String) IsZero() bool {
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return !s.Valid
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}
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