Function NewStructEncoder

structencoder.go:79–156

NewStructEncoder compiles a set of instructions for marhsaling a struct shape to a JSON document.

(t interface{})

// NewStructEncoder compiles a set of instructions for marhsaling a struct shape to a JSON document.
func NewStructEncoder(t interface{}) *StructEncoder {
	e := &StructEncoder{}
	e.t = t
	tt := reflect.TypeOf(t)

	e.chunk("{")

	emit := 0 // track number of fields we emit
	// pass over each field in the struct to build up our instruction set for each
	for e.i = 0; e.i < tt.NumField(); e.i++ {
		e.f = tt.Field(e.i)

		tag, opts := parseTag(e.f.Tag.Get("json")) // we're using tags to nominate inclusion
		if tag == "" {
			continue
		}
		emit++

		// write the key
		if emit > 1 {
			e.chunk(",")
		}
		e.chunk(`"` + tag + `":`)

		switch {
		/// support calling .String() when the 'stringer' option is passed
		case opts.Contains("stringer") && reflect.ValueOf(e.t).Field(e.i).MethodByName("String").Kind() != reflect.Invalid:
			e.optInstrStringer()

		/// support calling .JSONEncode(*Buffer) when the 'encoder' option is passed
		case opts.Contains("encoder"):

			// requrie explicit opt-in for JSONMarshaler implementation
			t := reflect.ValueOf(e.t).Field(e.i).Type()
			if t.Kind() != reflect.Ptr {
				t = reflect.PtrTo(t)
			}

			if _, ok := t.MethodByName("EncodeJSON"); ok {
				e.optInstrEncoderWriter()
				break
			}

			// default to JSONEncoder implementation for any other encoder fields
			e.optInstrEncoder()

		/// support writing byteslice-like items using 'raw' option.
		case opts.Contains("raw"):
			e.optInstrRaw()

		/// suport escaping reserved json characters from byteslice-like items and slices
		case opts.Contains("escape"):
			e.optInstrEscape()

		/// time is a type of struct, not a kind, so somewhat of a special case here.
		case e.f.Type == timeType:
			e.chunk(`"`)
			e.val(ptrTimeToBuf)