Golang Value.Kind方法代码示例

func (p *printer) marshalSimple(typ reflect.Type, val reflect.Value) (string, []byte, error) {
	switch val.Kind() {
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		return strconv.FormatInt(val.Int(), 10), nil, nil
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
		return strconv.FormatUint(val.Uint(), 10), nil, nil
	case reflect.Float32, reflect.Float64:
		return strconv.FormatFloat(val.Float(), 'g', -1, val.Type().Bits()), nil, nil
	case reflect.String:
		return val.String(), nil, nil
	case reflect.Bool:
		return strconv.FormatBool(val.Bool()), nil, nil
	case reflect.Array:
		if typ.Elem().Kind() != reflect.Uint8 {
			break
		}
		// [...]byte
		var bytes []byte
		if val.CanAddr() {
			bytes = val.Slice(0, val.Len()).Bytes()
		} else {
			bytes = make([]byte, val.Len())
			reflect.Copy(reflect.ValueOf(bytes), val)
		}
		return "", bytes, nil
	case reflect.Slice:
		if typ.Elem().Kind() != reflect.Uint8 {
			break
		}
		// []byte
		return "", val.Bytes(), nil
	}
	return "", nil, &UnsupportedTypeError{typ}
}

func GetColVals(val reflect.Value, cols []string) (values []string, err error) {
	typ := val.Type()
	// if not struct, then must just have one column.
	if val.Kind() != reflect.Struct && len(cols) != 1 {
		return nil, fmt.Errorf("GetColVals> If not a struct(%s), must have one column: %v", val.Kind(), cols)
	}

	values = make([]string, len(cols))
	for i, col := range cols {
		var fieldVal reflect.Value
		if val.Kind() == reflect.Struct {
			fieldIndex := getFieldIndexByName(typ, col)
			if fieldIndex[0] < 0 {
				return nil, fmt.Errorf("GetColVals> Can't found struct field(column): '%s'\n", col)
			}
			fieldVal = val.FieldByIndex(fieldIndex)
		} else {
			fieldVal = val
		}

		if values[i], err = GetValQuoteStr(fieldVal); err != nil {
			return
		}
	}

	return
}

func ReturnWhenSet(a, k interface{}) interface{} {
	av, isNil := indirect(reflect.ValueOf(a))
	if isNil {
		return ""
	}

	var avv reflect.Value
	switch av.Kind() {
	case reflect.Array, reflect.Slice:
		index, ok := k.(int)
		if ok && av.Len() > index {
			avv = av.Index(index)
		}
	case reflect.Map:
		kv := reflect.ValueOf(k)
		if kv.Type().AssignableTo(av.Type().Key()) {
			avv = av.MapIndex(kv)
		}
	}

	if avv.IsValid() {
		switch avv.Kind() {
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
			return avv.Int()
		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
			return avv.Uint()
		case reflect.Float32, reflect.Float64:
			return avv.Float()
		case reflect.String:
			return avv.String()
		}
	}

	return ""
}

func setValue(dstVal reflect.Value, src interface{}) {
	if dstVal.Kind() == reflect.Ptr {
		dstVal = reflect.Indirect(dstVal)
	}
	srcVal := reflect.ValueOf(src)

	if !srcVal.IsValid() { // src is literal nil
		if dstVal.CanAddr() {
			// Convert to pointer so that pointer's value can be nil'ed
			//                     dstVal = dstVal.Addr()
		}
		dstVal.Set(reflect.Zero(dstVal.Type()))

	} else if srcVal.Kind() == reflect.Ptr {
		if srcVal.IsNil() {
			srcVal = reflect.Zero(dstVal.Type())
		} else {
			srcVal = reflect.ValueOf(src).Elem()
		}
		dstVal.Set(srcVal)
	} else {
		dstVal.Set(srcVal)
	}

}

// Validates that if a value is provided for a field, that value must be at
// least a minimum length.
func validateFieldMin(f reflect.StructField, fvalue reflect.Value) error {
	minStr := f.Tag.Get("min")
	if minStr == "" {
		return nil
	}
	min, _ := strconv.ParseInt(minStr, 10, 64)

	kind := fvalue.Kind()
	if kind == reflect.Ptr {
		if fvalue.IsNil() {
			return nil
		}
		fvalue = fvalue.Elem()
	}

	switch fvalue.Kind() {
	case reflect.String:
		if int64(fvalue.Len()) < min {
			return fmt.Errorf("field too short, minimum length %d", min)
		}
	case reflect.Slice, reflect.Map:
		if fvalue.IsNil() {
			return nil
		}
		if int64(fvalue.Len()) < min {
			return fmt.Errorf("field too short, minimum length %d", min)
		}

		// TODO min can also apply to number minimum value.

	}
	return nil
}

// rv must be a non-nil pointer or a settable value
func indirect(rv reflect.Value) (reflect.Value, error) {
	for {
		if rv.Kind() == reflect.Interface && !rv.IsNil() {
			if e := rv.Elem(); e.Kind() == reflect.Ptr && !e.IsNil() {
				rv = e.Elem()
			}
		}

		if rv.Kind() == reflect.Map && rv.IsNil() {
			rv.Set(reflect.MakeMap(rv.Type()))
		}

		if rv.Kind() != reflect.Ptr {
			break
		}

		if rv.IsNil() {
			rv.Set(reflect.New(rv.Type().Elem()))
		}
		rv = rv.Elem()
	}
	if k := rv.Kind(); k != reflect.Struct && k != reflect.Map {
		return reflect.Value{}, &InvalidIndirectError{rv.Type()}
	}
	if rv.Kind() == reflect.Map {
		if t := rv.Type(); t.Key().Kind() != reflect.String || t.Elem().Kind() != reflect.String {
			return reflect.Value{}, &InvalidIndirectError{t}
		}
	}
	return rv, nil
}

func (mssql) SqlTag(value reflect.Value, size int, autoIncrease bool) string {
	switch value.Kind() {
	case reflect.Bool:
		return "bit"
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uintptr:
		if autoIncrease {
			return "int IDENTITY(1,1)"
		}
		return "int"
	case reflect.Int64, reflect.Uint64:
		if autoIncrease {
			return "bigint IDENTITY(1,1)"
		}
		return "bigint"
	case reflect.Float32, reflect.Float64:
		return "float"
	case reflect.String:
		if size > 0 && size < 65532 {
			return fmt.Sprintf("nvarchar(%d)", size)
		}
		return "text"
	case reflect.Struct:
		if _, ok := value.Interface().(time.Time); ok {
			return "datetime2"
		}
	default:
		if _, ok := value.Interface().([]byte); ok {
			if size > 0 && size < 65532 {
				return fmt.Sprintf("varchar(%d)", size)
			}
			return "text"
		}
	}
	panic(fmt.Sprintf("invalid sql type %s (%s) for mssql", value.Type().Name(), value.Kind().String()))
}

func encodeField(w io.Writer, f reflect.Value) error {
	if f.Type() == timeType {
		return encodeTime(w, f)
	}

	switch f.Kind() {
	case reflect.Uint8:
		fallthrough
	case reflect.Uint16:
		fallthrough
	case reflect.Uint32:
		fallthrough
	case reflect.Uint64:
		fallthrough
	case reflect.Int64:
		fallthrough
	case reflect.Int32:
		fallthrough
	case reflect.Int16:
		fallthrough
	case reflect.Int8:
		return binary.Write(w, byteOrder, f.Interface())
	case reflect.String:
		return encodeStrField(w, f)
	case reflect.Slice:
		return encodeArray(w, f)
	case reflect.Interface:
		return encodeField(w, f.Elem())
	default:
		panic(fmt.Sprintf("unimplemented kind %v", f))
	}
}

func unflattenValue(v reflect.Value, t reflect.Type) reflect.Value {
	// When t is an Interface, we can't do much, since we don't know the
	// original (unflattened) type of the value placed in v, so we just nop it.
	if t.Kind() == reflect.Interface {
		return v
	}
	// v can be invalid, if it holds the nil value for pointer type
	if !v.IsValid() {
		return v
	}
	// Make sure v is indeed flat
	if v.Kind() == reflect.Ptr {
		panic("unflattening non-flat value")
	}
	// Add a *, one at a time
	for t.Kind() == reflect.Ptr {
		if v.CanAddr() {
			v = v.Addr()
		} else {
			pw := reflect.New(v.Type())
			pw.Elem().Set(v)
			v = pw
		}
		t = t.Elem()
	}
	return v
}

func (m *mapper) unpackValue(keys []string, values []interface{}, out reflect.Value) error {
	switch out.Kind() {
	case reflect.Ptr:
		if out.IsNil() {
			out.Set(reflect.New(out.Type().Elem()))
		}
		return m.unpackValue(keys, values, reflect.Indirect(out))
	case reflect.Slice:
		if keys == nil {
			return m.unpackSimple(nil, values, out)
		} else {
			return m.unpackSlice(keys, values, out)
		}
	case reflect.Struct:
		return m.unpackStruct(keys, values, out)
	case reflect.Map:
		if keys == nil {
			return m.unpackSimple(nil, values, out)
		} else {
			return m.unpackMap(keys, values, out)
		}
	default:
		return m.unpackSimple(nil, values, out)
	}
	return fmt.Errorf("cannot unpack result to %T (%s)", out, out.Kind())
}

// NotNilFilter returns true for field values that are not nil;
// it returns false otherwise.
func NotNilFilter(_ string, v reflect.Value) bool {
	switch v.Kind() {
	case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice:
		return !v.IsNil()
	}
	return true
}

func (scope *Scope) callMethod(methodName string, reflectValue reflect.Value) {
	// Only get address from non-pointer
	if reflectValue.CanAddr() && reflectValue.Kind() != reflect.Ptr {
		reflectValue = reflectValue.Addr()
	}

	if methodValue := reflectValue.MethodByName(methodName); methodValue.IsValid() {
		switch method := methodValue.Interface().(type) {
		case func():
			method()
		case func(*Scope):
			method(scope)
		case func(*DB):
			newDB := scope.NewDB()
			method(newDB)
			scope.Err(newDB.Error)
		case func() error:
			scope.Err(method())
		case func(*Scope) error:
			scope.Err(method(scope))
		case func(*DB) error:
			newDB := scope.NewDB()
			scope.Err(method(newDB))
			scope.Err(newDB.Error)
		default:
			scope.Err(fmt.Errorf("unsupported function %v", methodName))
		}
	}
}

// callSliceRequired returns true if CallSlice is required instead of Call.
func callSliceRequired(param reflect.Type, val reflect.Value) bool {
	vt := val.Type()
	for param.Kind() == reflect.Slice {
		if val.Kind() == reflect.Interface {
			val = reflect.ValueOf(val.Interface())
			vt = val.Type()
		}

		if vt.Kind() != reflect.Slice {
			return false
		}

		vt = vt.Elem()
		if val.Kind() != reflect.Invalid {
			if val.Len() > 0 {
				val = val.Index(0)
			} else {
				val = reflect.Value{}
			}
		}
		param = param.Elem()
	}

	return true
}

func (d *decoder) parse_unmarshaler(v reflect.Value) bool {
	m, ok := v.Interface().(Unmarshaler)
	if !ok {
		// T doesn't work, try *T
		if v.Kind() != reflect.Ptr && v.CanAddr() {
			m, ok = v.Addr().Interface().(Unmarshaler)
			if ok {
				v = v.Addr()
			}
		}
	}
	if ok && (v.Kind() != reflect.Ptr || !v.IsNil()) {
		if d.read_one_value() {
			err := m.UnmarshalBencode(d.buf.Bytes())
			d.buf.Reset()
			if err != nil {
				panic(&UnmarshalerError{v.Type(), err})
			}
			return true
		}
		d.buf.Reset()
	}

	return false
}

// All protocol buffer fields are nillable, but be careful.
func isNil(v reflect.Value) bool {
	switch v.Kind() {
	case reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice:
		return v.IsNil()
	}
	return false
}