Golang StructTag.Get方法代码示例

func parseTag(tag reflect.StructTag) packopts {
	var opts packopts

	bpTag := tag.Get("binpack")

	for _, t := range strings.Split(string(bpTag), ",") {
		if t == "-" {
			opts.skip = true
		}
		if strings.HasPrefix(t, "lenprefix=") {
			opts.lenprefix = strings.TrimPrefix(t, "lenprefix=")
		}
		if strings.HasPrefix(t, "endian=") {
			endian := strings.TrimPrefix(t, "endian=")
			switch endian {
			case "little":
				opts.endian = binary.LittleEndian
			case "big":
				opts.endian = binary.BigEndian
			default:
				panic("unknown endian type in struct: " + endian)
			}
		}
	}

	return opts
}

func (q *queryParser) parseValue(v url.Values, value reflect.Value, prefix string, tag reflect.StructTag) error {
	value = elemOf(value)

	// no need to handle zero values
	if !value.IsValid() {
		return nil
	}

	t := tag.Get("type")
	if t == "" {
		switch value.Kind() {
		case reflect.Struct:
			t = "structure"
		case reflect.Slice:
			t = "list"
		case reflect.Map:
			t = "map"
		}
	}

	switch t {
	case "structure":
		return q.parseStruct(v, value, prefix)
	case "list":
		return q.parseList(v, value, prefix, tag)
	case "map":
		return q.parseMap(v, value, prefix, tag)
	default:
		return q.parseScalar(v, value, prefix, tag)
	}
}

func dump(path string, typ types.Type, st reflect.StructTag) IObj {
	named, _ := typ.(*types.Named)
	if named != nil {
		typ = typ.Underlying()
	}

	if strings.Split(st.Get("json"), ",")[0] == "" {
		if _, ok := typ.(*types.Struct); !ok {
			if _, ok := typ.(*types.Pointer); !ok {
				return nil
			}
		}
	}

	switch u := typ.(type) {
	case *types.Struct:
		return Struct(path, st, u, named)

	case *types.Map:
		return Map(path, st, u, named)

	case *types.Slice:
		return Slice(path, st, u)

	case *types.Pointer:
		return Pointer(path, st, u)

	case *types.Basic:
		return Basic(path, st, u, named)

	default:
		panic("unsupported")
	}
}

func HasFilter(field reflect.StructTag) (k, v string, err error) {
	tag := field.Get("blueprint")
	for _, entry := range strings.Split(tag, ",") {
		if strings.HasPrefix(entry, "filter") {
			if !strings.HasPrefix(entry, "filter(") || !strings.HasSuffix(entry, ")") {
				return "", "", fmt.Errorf("unexpected format for filter %q: missing ()", entry)
			}
			entry = strings.TrimPrefix(entry, "filter(")
			entry = strings.TrimSuffix(entry, ")")

			s := strings.Split(entry, ":")
			if len(s) != 2 {
				return "", "", fmt.Errorf("unexpected format for filter %q: expected single ':'", entry)
			}
			k = s[0]
			v, err = strconv.Unquote(s[1])
			if err != nil {
				return "", "", fmt.Errorf("unexpected format for filter %q: %s", entry, err.Error())
			}
			return k, v, nil
		}
	}

	return "", "", nil
}

// Iterate struct names and return a slice that contains column names.
func ParseColumnNames(val interface{}) ([]string) {
	t := reflect.ValueOf(val).Elem()
	typeOfT := t.Type()

	var structName string = typeOfT.String()
	if cache, ok := columnNameCache[structName] ; ok {
		return cache
	}

	var columns []string
	for i := 0; i < t.NumField(); i++ {
		var tag reflect.StructTag = typeOfT.Field(i).Tag

		if tag.Get("field") == "-" {
			continue
		}

		var columnName *string = GetColumnNameFromTag(&tag)
		if columnName == nil {
			continue
		}
		columns = append(columns, *columnName)
	}
	columnNameCache[structName] = columns
	return columns
}

// NewParamOptions returns a ParamOptions from a StructTag
func NewParamOptions(tags *reflect.StructTag) *ParamOptions {
	output := &ParamOptions{}

	// We use the json tag to get the field name
	jsonOpts := strings.Split(tags.Get("json"), ",")
	if len(jsonOpts) > 0 {
		if jsonOpts[0] == "-" {
			return &ParamOptions{Ignore: true}
		}

		output.Name = jsonOpts[0]
	}

	// We parse the params
	opts := strings.Split(tags.Get("params"), ",")
	nbOptions := len(opts)
	for i := 0; i < nbOptions; i++ {
		switch opts[i] {
		case "required":
			output.Required = true
		case "trim":
			output.Trim = true
		}
	}

	return output
}

func generateInput(tag reflect.StructTag, valueField string) (fInput string) {
	var extras, label string

	// Ignore "-" form fields
	if tag.Get("form") == "-" || tag.Get("form") == "" {
		return
	}

	fType := "text"
	fAttrs := strings.Split(tag.Get("attr"), ";")
	for _, element := range fAttrs {
		fAttr := strings.Split(element, ":")
		ele := strings.ToLower(fAttr[0])

		val := ""
		if len(fAttr) == 2 {
			val = fAttr[1]
		}
		if valueField != "" && val == "input" {
			val = valueField
		}
		if valueField == "" && val == "input" {
			val = ""
		}

		switch ele {
		case "alt":
			extras += fmt.Sprintf(" alt=\"%s\"", val)
		case "autofocus":
			extras += " autofocus"
		case "checked":
			extras += " checked"
		case "class":
			extras += fmt.Sprintf(" class=\"%s\"", val)
		case "label":
			label = fmt.Sprintf("\t<label for=\"%s\">%s</label>\n", tag.Get("form"), val)
		case "maxlength":
			extras += fmt.Sprintf(" maxlength=\"%s\"", val)
		case "min":
			extras += fmt.Sprintf(" min=\"%s\"", val)
		case "placeholder":
			extras += fmt.Sprintf(" placeholder=\"%s\"", val)
		case "readonly":
			extras += " readonly"
		case "required":
			extras += " required"
		case "type":
			fType = val
		case "value":
			extras += fmt.Sprintf(" value=\"%s\"", val)
		}
	}

	if label != "" {
		fInput += label
	}

	fInput += fmt.Sprintf("\t<input type=\"%s\" name=\"%s\" id=\"%s\"%s>\n", fType, tag.Get("form"), tag.Get("form"), extras)
	return
}

// parseTag parses "endpoints" field tag into endpointsTag struct.
//
//   type MyMessage struct {
//       SomeField int `endpoints:"req,min=0,max=100,desc="Int field"`
//       WithDefault string `endpoints:"d=Hello gopher"`
//   }
//
//   - req, required (boolean)
//   - d=val, default value
//   - min=val, min value
//   - max=val, max value
//   - desc=val, description
//
// It is an error to specify both default and required.
func parseTag(t reflect.StructTag) (*endpointsTag, error) {
	eTag := &endpointsTag{}
	if tag := t.Get("endpoints"); tag != "" {
		parts := strings.Split(tag, ",")
		for _, k := range parts {
			switch k {
			case "req":
				eTag.required = true
			default:
				// key=value format
				kv := strings.SplitN(k, "=", 2)
				if len(kv) < 2 {
					continue
				}
				switch kv[0] {
				case "d":
					eTag.defaultVal = kv[1]
				case "min":
					eTag.minVal = kv[1]
				case "max":
					eTag.maxVal = kv[1]
				case "desc":
					eTag.desc = kv[1]
				}
			}
		}
		if eTag.required && eTag.defaultVal != "" {
			return nil, fmt.Errorf(
				"Can't have both required and default (%#v)",
				eTag.defaultVal)
		}
	}
	return eTag, nil
}

func parse(r reflect.Value, node *XMLNode, tag reflect.StructTag) error {
	rtype := r.Type()
	if rtype.Kind() == reflect.Ptr {
		rtype = rtype.Elem() // check kind of actual element type
	}

	t := tag.Get("type")
	if t == "" {
		switch rtype.Kind() {
		case reflect.Struct:
			t = "structure"
		case reflect.Slice:
			t = "list"
		case reflect.Map:
			t = "map"
		}
	}

	switch t {
	case "structure":
		if field, ok := rtype.FieldByName("SDKShapeTraits"); ok {
			tag = field.Tag
		}
		return parseStruct(r, node, tag)
	case "list":
		return parseList(r, node, tag)
	case "map":
		return parseMap(r, node, tag)
	default:
		return parseScalar(r, node, tag)
	}
}

func (b *xmlBuilder) buildValue(value reflect.Value, current *XMLNode, tag reflect.StructTag) error {
	value = elemOf(value)
	if !value.IsValid() { // no need to handle zero values
		return nil
	} else if tag.Get("location") != "" { // don't handle non-body location values
		return nil
	}

	t := tag.Get("type")
	if t == "" {
		switch value.Kind() {
		case reflect.Struct:
			t = "structure"
		case reflect.Slice:
			t = "list"
		case reflect.Map:
			t = "map"
		}
	}

	switch t {
	case "structure":
		if field, ok := value.Type().FieldByName("SDKShapeTraits"); ok {
			tag = tag + reflect.StructTag(" ") + field.Tag
		}
		return b.buildStruct(value, current, tag)
	case "list":
		return b.buildList(value, current, tag)
	case "map":
		return b.buildMap(value, current, tag)
	default:
		return b.buildScalar(value, current, tag)
	}
}

// parseTag parses the given struct tag attached to the given
// field name into a tag structure.
func parseTag(rtag reflect.StructTag, fieldName string) (tag, error) {
	t := tag{
		name: fieldName,
	}
	tagStr := rtag.Get("httprequest")
	if tagStr == "" {
		return t, nil
	}
	fields := strings.Split(tagStr, ",")
	if fields[0] != "" {
		t.name = fields[0]
	}
	for _, f := range fields[1:] {
		switch f {
		case "path":
			t.source = sourcePath
		case "form":
			t.source = sourceForm
		case "body":
			t.source = sourceBody
		default:
			return tag{}, fmt.Errorf("unknown tag flag %q", f)
		}
	}
	return t, nil
}

func (source envSource) GetConfig(name string, tag reflect.StructTag) (interface{}, bool) {
	var varName = tag.Get("env")
	if varName == "" {
		return nil, false
	}
	return os.Getenv(varName) == "1", true
}

func buildStruct(value reflect.Value, buf *bytes.Buffer, tag reflect.StructTag) error {
	if !value.IsValid() {
		return nil
	}

	// unwrap payloads
	if payload := tag.Get("payload"); payload != "" {
		field, _ := value.Type().FieldByName(payload)
		tag = field.Tag
		value = elemOf(value.FieldByName(payload))

		if !value.IsValid() {
			return nil
		}
	}

	buf.WriteString("{")

	t, fields := value.Type(), []*reflect.StructField{}
	for i := 0; i < t.NumField(); i++ {
		field := t.Field(i)
		member := value.FieldByName(field.Name)
		if (member.Kind() == reflect.Ptr || member.Kind() == reflect.Slice || member.Kind() == reflect.Map) && member.IsNil() {
			continue // ignore unset fields
		}
		if c := field.Name[0:1]; strings.ToLower(c) == c {
			continue // ignore unexported fields
		}
		if field.Tag.Get("location") != "" {
			continue // ignore non-body elements
		}

		fields = append(fields, &field)
	}

	for i, field := range fields {
		member := value.FieldByName(field.Name)

		// figure out what this field is called
		name := field.Name
		if locName := field.Tag.Get("locationName"); locName != "" {
			name = locName
		}

		buf.WriteString(fmt.Sprintf("%q:", name))

		err := buildAny(member, buf, field.Tag)
		if err != nil {
			return err
		}

		if i < len(fields)-1 {
			buf.WriteString(",")
		}
	}

	buf.WriteString("}")

	return nil
}

func (w *writing) writeType(e ast.Expr, name string, tag reflect.StructTag) {
	switch e := e.(type) {
	case *ast.StructType:
		w.writeStruct(e, name)
	case *ast.SelectorExpr:
		pck := e.X.(*ast.Ident).Name
		s := e.Sel.Name
		w.writeNamed(pck+"."+s, name, tag)
	case *ast.StarExpr:
		w.writeType(e.X, name, tag)
	case *ast.Ident:
		w.writeNamed(e.Name, name, tag)
	case *ast.ArrayType:
		lT := tag.Get("length")
		if lT != "remaining" && lT != "" && lT[0] != '@' {
			w.writeNamed(lT, fmt.Sprintf("%s(len(%s))", lT, name), "")
		}
		if i, ok := e.Elt.(*ast.Ident); ok && (i.Name == "byte" || i.Name == "uint8") {
			fmt.Fprintf(&w.buf, "if _, err = ww.Write(%s); err != nil { return }\n", name)
		} else {
			iVar := w.tmp()
			fmt.Fprintf(&w.buf, "for %s := range %s {\n", iVar, name)
			w.writeType(e.Elt, fmt.Sprintf("%s[%s]", name, iVar), tag)
			w.buf.WriteString("}\n")
		}
	default:
		fmt.Fprintf(&w.buf, "// Unhandled %#v\n", e)
	}
}

// Extract column name attribute from struct tag (the first element) of the 'field' tag or
// column name from 'json' tag.
func GetColumnNameFromTag(tag *reflect.StructTag) *string {
	var p int
	var tagStr string
	if tagStr = tag.Get("field"); len(tagStr) != 0 {
		// ignore it if it starts with dash
		if tagStr[0] == "-"[0] {
			return nil
		}
		if p = IndexOfChar(tagStr, ","); p != -1 {
			if p > 1 {
				str := tagStr[:p]
				return &str
			}
		} else {
			return &tagStr
		}
	}

	if tagStr = tag.Get("json"); len(tagStr) == 0 {
		return nil
	}
	if tagStr[0] == "-"[0] {
		return nil
	}

	if p = IndexOfChar(tagStr, ","); p != -1 {
		if p > 1 {
			str := tagStr[:p]
			return &str
		}
		return nil
	}
	return &tagStr
}