opt.go

Documentation: github.com/mailru/easyjson/opt/optional

     1  // +build none
     2  
     3  package optional
     4  
     5  import (
     6  	"fmt"
     7  
     8  	"github.com/mailru/easyjson/jlexer"
     9  	"github.com/mailru/easyjson/jwriter"
    10  )
    11  
    12  // template type Optional(A)
    13  type A int
    14  
    15  // A 'gotemplate'-based type for providing optional semantics without using pointers.
    16  type Optional struct {
    17  	V       A
    18  	Defined bool
    19  }
    20  
    21  // Creates an optional type with a given value.
    22  func OOptional(v A) Optional {
    23  	return Optional{V: v, Defined: true}
    24  }
    25  
    26  // Get returns the value or given default in the case the value is undefined.
    27  func (v Optional) Get(deflt A) A {
    28  	if !v.Defined {
    29  		return deflt
    30  	}
    31  	return v.V
    32  }
    33  
    34  // MarshalEasyJSON does JSON marshaling using easyjson interface.
    35  func (v Optional) MarshalEasyJSON(w *jwriter.Writer) {
    36  	if v.Defined {
    37  		w.Optional(v.V)
    38  	} else {
    39  		w.RawString("null")
    40  	}
    41  }
    42  
    43  // UnmarshalEasyJSON does JSON unmarshaling using easyjson interface.
    44  func (v *Optional) UnmarshalEasyJSON(l *jlexer.Lexer) {
    45  	if l.IsNull() {
    46  		l.Skip()
    47  		*v = Optional{}
    48  	} else {
    49  		v.V = l.Optional()
    50  		v.Defined = true
    51  	}
    52  }
    53  
    54  // MarshalJSON implements a standard json marshaler interface.
    55  func (v Optional) MarshalJSON() ([]byte, error) {
    56  	w := jwriter.Writer{}
    57  	v.MarshalEasyJSON(&w)
    58  	return w.Buffer.BuildBytes(), w.Error
    59  }
    60  
    61  // UnmarshalJSON implements a standard json unmarshaler interface.
    62  func (v *Optional) UnmarshalJSON(data []byte) error {
    63  	l := jlexer.Lexer{Data: data}
    64  	v.UnmarshalEasyJSON(&l)
    65  	return l.Error()
    66  }
    67  
    68  // IsDefined returns whether the value is defined, a function is required so that it can
    69  // be used in an interface.
    70  func (v Optional) IsDefined() bool {
    71  	return v.Defined
    72  }
    73  
    74  // String implements a stringer interface using fmt.Sprint for the value.
    75  func (v Optional) String() string {
    76  	if !v.Defined {
    77  		return "<undefined>"
    78  	}
    79  	return fmt.Sprint(v.V)
    80  }
    81
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