mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2025-10-31 14:52:30 -05:00
81 lines
2.5 KiB
Go
81 lines
2.5 KiB
Go
|
// Copyright 2024 The Go Authors. All rights reserved.
|
||
|
|
// Use of this source code is governed by a BSD-style
|
||
|
|
// license that can be found in the LICENSE file.
|
||
|
|
|
||
|
|
package proto
|
||
|
|
|
||
|
|
// ValueOrNil returns nil if has is false, or a pointer to a new variable
|
||
|
|
// containing the value returned by the specified getter.
|
||
|
|
//
|
||
|
|
// This function is similar to the wrappers (proto.Int32(), proto.String(),
|
||
|
|
// etc.), but is generic (works for any field type) and works with the hasser
|
||
|
|
// and getter of a field, as opposed to a value.
|
||
|
|
//
|
||
|
|
// This is convenient when populating builder fields.
|
||
|
|
//
|
||
|
|
// Example:
|
||
|
|
//
|
||
|
|
// hop := attr.GetDirectHop()
|
||
|
|
// injectedRoute := ripb.InjectedRoute_builder{
|
||
|
|
// Prefixes: route.GetPrefixes(),
|
||
|
|
// NextHop: proto.ValueOrNil(hop.HasAddress(), hop.GetAddress),
|
||
|
|
// }
|
||
|
|
func ValueOrNil[T any](has bool, getter func() T) *T {
|
||
|
|
if !has {
|
||
|
|
return nil
|
||
|
|
}
|
||
|
|
v := getter()
|
||
|
|
return &v
|
||
|
|
}
|
||
|
|
|
||
|
|
// ValueOrDefault returns the protobuf message val if val is not nil, otherwise
|
||
|
|
// it returns a pointer to an empty val message.
|
||
|
|
//
|
||
|
|
// This function allows for translating code from the old Open Struct API to the
|
||
|
|
// new Opaque API.
|
||
|
|
//
|
||
|
|
// The old Open Struct API represented oneof fields with a wrapper struct:
|
||
|
|
//
|
||
|
|
// var signedImg *accountpb.SignedImage
|
||
|
|
// profile := &accountpb.Profile{
|
||
|
|
// // The Avatar oneof will be set, with an empty SignedImage.
|
||
|
|
// Avatar: &accountpb.Profile_SignedImage{signedImg},
|
||
|
|
// }
|
||
|
|
//
|
||
|
|
// The new Opaque API treats oneof fields like regular fields, there are no more
|
||
|
|
// wrapper structs:
|
||
|
|
//
|
||
|
|
// var signedImg *accountpb.SignedImage
|
||
|
|
// profile := &accountpb.Profile{}
|
||
|
|
// profile.SetSignedImage(signedImg)
|
||
|
|
//
|
||
|
|
// For convenience, the Opaque API also offers Builders, which allow for a
|
||
|
|
// direct translation of struct initialization. However, because Builders use
|
||
|
|
// nilness to represent field presence (but there is no non-nil wrapper struct
|
||
|
|
// anymore), Builders cannot distinguish between an unset oneof and a set oneof
|
||
|
|
// with nil message. The above code would need to be translated with help of the
|
||
|
|
// ValueOrDefault function to retain the same behavior:
|
||
|
|
//
|
||
|
|
// var signedImg *accountpb.SignedImage
|
||
|
|
// return &accountpb.Profile_builder{
|
||
|
|
// SignedImage: proto.ValueOrDefault(signedImg),
|
||
|
|
// }.Build()
|
||
|
|
func ValueOrDefault[T interface {
|
||
|
|
*P
|
||
|
|
Message
|
||
|
|
}, P any](val T) T {
|
||
|
|
if val == nil {
|
||
|
|
return T(new(P))
|
||
|
|
}
|
||
|
|
return val
|
||
|
|
}
|
||
|
|
|
||
|
|
// ValueOrDefaultBytes is like ValueOrDefault but for working with fields of
|
||
|
|
// type []byte.
|
||
|
|
func ValueOrDefaultBytes(val []byte) []byte {
|
||
|
|
if val == nil {
|
||
|
|
return []byte{}
|
||
|
|
}
|
||
|
|
return val
|
||
|
|
}
|