Function extractFields

inception/reflect.go:130–260

extractFields returns a list of fields that JSON should recognize for the given type. The algorithm is breadth-first search over the set of structs to include - the top struct and then any reachable anonymous structs.

(obj interface{})

// The algorithm is breadth-first search over the set of structs to include - the top struct
// and then any reachable anonymous structs.
func extractFields(obj interface{}) []*StructField {
	t := reflect.TypeOf(obj)
	// Anonymous fields to explore at the current level and the next.
	current := []StructField{}
	next := []StructField{{Typ: t}}

	// Count of queued names for current level and the next.
	count := map[reflect.Type]int{}
	nextCount := map[reflect.Type]int{}

	// Types already visited at an earlier level.
	visited := map[reflect.Type]bool{}

	// Fields found.
	var fields []*StructField

	for len(next) > 0 {
		current, next = next, current[:0]
		count, nextCount = nextCount, map[reflect.Type]int{}

		for _, f := range current {
			if visited[f.Typ] {
				continue
			}
			visited[f.Typ] = true

			// Scan f.typ for fields to include.
			for i := 0; i < f.Typ.NumField(); i++ {
				sf := f.Typ.Field(i)
				if sf.PkgPath != "" { // unexported
					continue
				}
				tag := sf.Tag.Get("json")
				if tag == "-" {
					continue
				}
				name, opts := parseTag(tag)
				if !isValidTag(name) {
					name = ""
				}

				ft := sf.Type
				ptr := false
				if ft.Kind() == reflect.Ptr {
					ptr = true
				}

				if ft.Name() == "" && ft.Kind() == reflect.Ptr {
					// Follow pointer.
					ft = ft.Elem()
				}

				// Record found field and index sequence.
				if name != "" || !sf.Anonymous || ft.Kind() != reflect.Struct {
					tagged := name != ""
					if name == "" {
						name = sf.Name
					}