Golang Field.Kind方法代碼示例

func (e *SelectionValidator) processField(fieldName string, field *structs.Field) error {
	fieldName += field.Name()
	switch field.Kind() {
	case reflect.Struct:
		// this is used for error messages below, when we have an error at the
		// child properties add parent properties into the error message as well
		fieldName += "."

		for _, f := range field.Fields() {
			if err := e.processField(fieldName, f); err != nil {
				return err
			}
		}
	default:
		if field.IsZero() {
			return nil
		}
		selectionStr := field.Tag(e.SelectTagName)
		if selectionStr == "" {
			return nil
		}

		err := validateSelection(field, selectionStr)
		if err != nil {
			return err
		}
	}

	return nil
}

// setFieldValue will try to set the value of a given field to v, which is
// given as string and converted to the field type as required.
func setFieldValue(field *structs.Field, v string) error {
	switch field.Kind() {
	case reflect.String:
		err := field.Set(v)
		if err != nil {
			return err
		}
	case reflect.Int, reflect.Int64:
		i, err := strconv.Atoi(v)
		if err != nil {
			return err
		}
		err = field.Set(i)
		if err != nil {
			return err
		}
	case reflect.Float64:
		f, err := strconv.ParseFloat(v, 64)
		if err != nil {
			return err
		}
		err = field.Set(f)
		if err != nil {
			return err
		}
	default:
		return fmt.Errorf("cannot set field value for field kind %s", field.Kind())
	}
	return nil
}

// processField gets leading name for the env variable and combines the current
// field's name and generates environemnt variable names recursively
func (e *EnvironmentLoader) processField(prefix string, field *structs.Field) error {
	fieldName := e.generateFieldName(prefix, field)

	switch {
	case field.Kind() == reflect.Struct && !implementsTextUnmarshaler(field):
		for _, f := range field.Fields() {
			if err := e.processField(fieldName, f); err != nil {
				return err
			}
		}
	case field.Kind() == reflect.Ptr:
		field.InitElem()
		return e.processField(prefix, field)
	default:
		v := os.Getenv(fieldName)
		if v == "" {
			return nil
		}

		if err := fieldSet(field, v); err != nil {
			return err
		}
	}

	return nil
}

func validateSelection(field *structs.Field, selection string) error {
	selectionSet := strings.Split(selection, "|")
	switch field.Kind() {
	case reflect.Int:
		i := field.Value().(int)
		s := strconv.Itoa(i)
		for _, selection := range selectionSet {
			if s == selection {
				return nil
			}
		}
		return fmt.Errorf("validate: Field %s value %s, not in selection %s.", field.Name(), s, selection)
	case reflect.String:
		s := field.Value().(string)
		for _, selection := range selectionSet {
			if s == selection {
				return nil
			}
		}
		return fmt.Errorf("validate: Field %s value %s, not in selection %s.", field.Name(), s, selection)
	default:
		return nil
	}
	return nil
}

// processField gets tagName and the field, recursively checks if the field has the given
// tag, if yes, sets it otherwise ignores
func (t *TagLoader) processField(tagName string, field *structs.Field) error {
	switch {
	case field.Kind() == reflect.Struct && !implementsTextUnmarshaler(field):
		for _, f := range field.Fields() {
			if err := t.processField(tagName, f); err != nil {
				return err
			}
		}
	case field.Kind() == reflect.Ptr:
		field.InitElem()
		return t.processField(tagName, field)
	default:
		defaultVal := field.Tag(t.DefaultTagName)
		if defaultVal == "" {
			return nil
		}

		err := fieldSet(field, defaultVal)
		if err != nil {
			return err
		}
	}

	return nil
}

// processField gets leading name for the env variable and combines the current
// field's name and generates environemnt variable names recursively
func (e *EnvironmentLoader) processField(prefix string, field *structs.Field) error {
	fieldName := e.generateFieldName(prefix, field)

	switch field.Kind() {
	case reflect.Struct:
		for _, f := range field.Fields() {
			if err := e.processField(fieldName, f); err != nil {
				return err
			}
		}
	default:
		envTag := field.Tag(e.EnvTagName)
		var v string
		if envTag != "" {
			v = os.Getenv(envTag)
		}
		if v == "" {
			v = os.Getenv(fieldName)
		}
		if v == "" {
			return nil
		}

		if err := fieldSet(field, v); err != nil {
			return err
		}
	}

	return nil
}

func (i *INILoader) setField(field *structs.Field, c *goconfig.ConfigFile, section string) error {
	//first process each subfield of a struct field
	switch field.Kind() {
	case reflect.Struct:
		for _, f := range field.Fields() {
			var subsection string
			if section == "" {
				subsection = field.Name()
			} else {
				subsection = section + "." + field.Name()
			}
			if err := i.setField(f, c, subsection); err != nil {
				return err
			}
		}
	default:
		v, err := c.GetValue(section, field.Name())
		if err == nil && v != "" {
			err := fieldSet(field, v)
			if err != nil {
				return err
			}
		}
	}

	return nil
}

// processField gets tagName and the field, recursively checks if the field has the given
// tag, if yes, sets it otherwise ignores
func (t *TagLoader) processFieldDefaultValue(field *structs.Field) error {

	//first process each subfield of a struct field
	switch field.Kind() {
	case reflect.Struct:
		for _, f := range field.Fields() {
			if err := t.processFieldDefaultValue(f); err != nil {
				return err
			}
		}
	default:
		//Set default value for the field itself, including struct field
		// If there's a default value tag for struct field, it should be in Json format
		defaultVal := field.Tag(t.DefaultTagName)
		if defaultVal == "" {
			return nil
		}

		err := fieldSet(field, defaultVal)
		if err != nil {
			return err
		}
	}

	return nil
}

func parseValue(field *structs.Field, val string) (interface{}, error) {
	switch field.Kind() {
	case reflect.Int:
		v, err := strconv.Atoi(val)
		if err != nil {
			return nil, err
		}
		return v, nil
	case reflect.Float64:
		v, err := strconv.ParseFloat(val, 64)
		if err != nil {
			return nil, err
		}
		return v, nil
	case reflect.Bool:
		v, err := strconv.ParseBool(val)
		if err != nil {
			return nil, err
		}
		return v, nil
	default:
		fieldVal := field.Value()

		if _, casted := fieldVal.(bson.ObjectId); casted {
			if bson.IsObjectIdHex(val) {
				return bson.ObjectIdHex(val), nil
			} else {
				return nil, fmt.Errorf("should be bson.ObjectId hex")
			}
		}
		if _, casted := (fieldVal).(time.Time); casted {
			v := &time.Time{}
			return v, v.UnmarshalText([]byte(val))
		}
		if convertable, casted := fieldVal.(Converter); casted {
			converted, err := convertable.Convert(val)
			if err != nil {
				return nil, err
			}
			if enum, casted := fieldVal.(Enumer); casted {
				enumValues := enum.Enum()
				for _, eV := range enumValues {
					if eV == converted {
						return converted, nil
					}
				}
				return nil, fmt.Errorf("should be one of %v", enumValues)
			}
			return converted, nil
		}
		return val, nil
	}

}

func validateString(field *structs.Field, regex string) error {
	switch field.Kind() {
	case reflect.String:
		i := field.Value().(string)
		matched, err := regexp.MatchString(regex, i)
		if err == nil && !matched {
			return fmt.Errorf("validate: Field %s value %s, regex %s not matched.", field.Name(), i, regex)
		}
	}

	return nil
}

// printField prints the field of the config struct for the flag.Usage
func (e *EnvironmentLoader) printField(prefix string, field *structs.Field) {
	fieldName := e.generateFieldName(prefix, field)

	switch field.Kind() {
	case reflect.Struct:
		for _, f := range field.Fields() {
			e.printField(fieldName, f)
		}
	default:
		fmt.Println("  ", fieldName)
	}
}

// printField prints the field of the config struct for the flag.Usage
func (e *EnvironmentLoader) printField(prefix string, field *structs.Field) {
	fieldName := e.generateFieldName(prefix, field)

	if field.IsExported() {
		switch {
		case field.Kind() == reflect.Struct && !implementsTextUnmarshaler(field):
			for _, f := range field.Fields() {
				e.printField(fieldName, f)
			}
		default:
			fmt.Println("  ", fieldName)
		}
	}
}

// processField generates a flag based on the given field and fieldName. If a
// nested struct is detected, a flag for each field of that nested struct is
// generated too.
func (f *FlagLoader) processField(fieldName string, field *structs.Field) error {
	if f.CamelCase {
		fieldName = strings.Join(camelcase.Split(fieldName), "-")
	}

	switch field.Kind() {
	case reflect.Struct:
		for _, ff := range field.Fields() {
			flagName := field.Name() + "-" + ff.Name()

			if f.Flatten {
				// first check if it's set or not, because if we have duplicate
				// we don't want to break the flag. Panic by giving a readable
				// output
				f.flagSet.VisitAll(func(fl *flag.Flag) {
					if strings.ToLower(ff.Name()) == fl.Name {
						// already defined
						panic(fmt.Sprintf("flag '%s' is already defined in outer struct", fl.Name))
					}
				})

				flagName = ff.Name()
			}

			if err := f.processField(flagName, ff); err != nil {
				return err
			}
		}
	default:
		// Add custom prefix to the flag if it's set
		if f.Prefix != "" {
			fieldName = f.Prefix + "-" + fieldName
		}

		// we only can get the value from expored fields, unexported fields panics
		if field.IsExported() {
			// use built-in or custom flag usage message
			flagUsageFunc := flagUsageDefault
			if f.FlagUsageFunc != nil {
				flagUsageFunc = f.FlagUsageFunc
			}
			f.flagSet.Var(newFieldValue(field), flagName(fieldName), flagUsageFunc(fieldName))
		}
	}

	return nil
}

// fieldSet sets field value from the given string value. It converts the
// string value in a sane way and is usefulf or environment variables or flags
// which are by nature in string types.
func fieldSet(field *structs.Field, v string) error {
	// TODO: add support for other types
	switch field.Kind() {
	case reflect.Bool:
		val, err := strconv.ParseBool(v)
		if err != nil {
			return err
		}

		if err := field.Set(val); err != nil {
			return err
		}
	case reflect.Int:
		i, err := strconv.Atoi(v)
		if err != nil {
			return err
		}

		if err := field.Set(i); err != nil {
			return err
		}
	case reflect.String:
		field.Set(v)
	case reflect.Slice:
		// TODO add other typed slice support
		if _, ok := field.Value().([]string); !ok {
			return errors.New("can't set on non string slices")
		}

		if err := field.Set(strings.Split(v, ",")); err != nil {
			return err
		}
	case reflect.Float64:
		f, err := strconv.ParseFloat(v, 64)
		if err != nil {
			return err
		}

		if err := field.Set(f); err != nil {
			return err
		}
	default:
		return fmt.Errorf("multiconfig: not supported type: %s", field.Kind())
	}

	return nil
}

func validateLength(field *structs.Field, minlenStr string, maxlenStr string) error {
	switch field.Kind() {
	case reflect.String:
		i := field.Value().(string)
		l := len(i)

		min, minErr := strconv.Atoi(minlenStr)
		max, maxErr := strconv.Atoi(maxlenStr)
		if (minErr == nil && l < min) || (maxErr == nil && l > max) {
			return fmt.Errorf("validate: Field %s value %s, length limit: [%s, %s]", field.Name(), i, minlenStr, maxlenStr)
		}
	default:
		return nil
	}

	return nil
}