89 lines
2.2 KiB
Go
89 lines
2.2 KiB
Go
// Package null provides a convenient way of handling null values.
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// Types in this package consider empty or zero input the same as null input.
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// Types in this package will encode to their zero value, even if null.
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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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)
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// String is a nullable string.
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type String struct {
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sql.NullString
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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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// StringFrom creates a new String that will be null if s is blank.
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func StringFrom(s string) String {
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return NewString(s, s != "")
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}
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// StringFrom creates a new String that be null if s is nil or blank.
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// It will make s point to the String's value.
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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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str := NewString(*s, *s != "")
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return str
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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 produces 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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json.Unmarshal(data, &v)
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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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}
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s.Valid = (err == nil) && (s.String != "")
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return err
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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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// Pointer 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 or empty strings, for future omitempty support. (Go 1.4?)
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func (s String) IsZero() bool {
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return !s.Valid || s.String == ""
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}
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