@ -66,7 +66,7 @@ Singular fields (of all types) track presence explicitly in the generated API. T
Similar to singular fields, `oneof` fields explicitly track which one of the members, if any, contains a value. For example, consider this example `oneof`:
```
```protobuf
oneof foo {
int32 a = 1;
float b = 2;
@ -144,7 +144,7 @@ This change may or may not be safe, depending on the application's semantics. Fo
Client A uses this definition of the message, which follows the _explicit presence_ serialization discipline for field `foo`:
```
```protobuf
syntax = "proto3";
message Msg {
optional int32 foo = 1;
@ -153,7 +153,7 @@ message Msg {
Client B uses a definition of the same message, except that it follows the _no presence_ discipline:
```
```protobuf
syntax = "proto3";
message Msg {
int32 foo = 1;
@ -162,7 +162,7 @@ message Msg {
Now, consider a scenario where client A observes `foo`'s presence as the clients repeatedly exchange the "same" message by deserializing and reserializing:
```
```protobuf
// Client A:
Msg m_a;
m_a.set_foo(1); // non-default value
@ -208,7 +208,7 @@ These are the general steps to use the experimental field tracking support for p
This is an example of a proto3 message with fields which follow both _no presence_ and _explicit presence_ semantics:
```
```protobuf
syntax = "proto3";
package example;
@ -231,7 +231,7 @@ The generated code for proto3 fields with _explicit presence_ (the `optional` la
This is the definition used in the "no presence" examples below:
```
```protobuf
syntax = "proto3";
package example;
message Msg {
@ -241,7 +241,7 @@ message Msg {
This is the definition used in the "explicit presence" examples below:
```
```protobuf
syntax = "proto3";
package example;
message Msg {
@ -255,7 +255,7 @@ In the examples, a function `GetProto` constructs and returns a message of type
No presence:
```
```C++
Msg m = GetProto();
if (m.foo() != 0) {
// "Clear" the field:
@ -268,7 +268,7 @@ if (m.foo() != 0) {
Explicit presence:
```
```C++
Msg m = GetProto();
if (m.has_foo()) {
// Clear the field:
@ -283,7 +283,7 @@ if (m.has_foo()) {
No presence:
```
```C#
var m = GetProto();
if (m.Foo != 0) {
// "Clear" the field:
@ -296,7 +296,7 @@ if (m.Foo != 0) {
Explicit presence:
```
```C#
var m = GetProto();
if (m.HasFoo) {
// Clear the field:
@ -311,7 +311,7 @@ if (m.HasFoo) {
No presence:
```
```go
m := GetProto()
if m.Foo != 0 {
// "Clear" the field:
@ -324,7 +324,7 @@ if m.Foo != 0 {
Explicit presence:
```
```go
m := GetProto()
if m.Foo != nil {
// Clear the field:
@ -341,7 +341,7 @@ These examples use a `Builder` to demonstrate clearing. Simply checking presence
No presence:
```
```java
Msg.Builder m = GetProto().toBuilder();
if (m.getFoo() != 0) {
// "Clear" the field:
@ -354,7 +354,7 @@ if (m.getFoo() != 0) {
Explicit presence:
```
```java
Msg.Builder m = GetProto().toBuilder();
if (m.hasFoo()) {
// Clear the field:
@ -369,25 +369,25 @@ if (m.hasFoo()) {
No presence:
```
```python
m = example.Msg()
if m.foo != 0:
// "Clear" the field:
# "Clear" the field:
m.foo = 0
else:
// Default value: field may not have been present.
# Default value: field may not have been present.
m.foo = 1
```
Explicit presence:
```
```python
m = example.Msg()
if m.HasField('foo'):
// Clear the field:
# Clear the field:
m.ClearField('foo')
else:
// Field is not present, so set it.
# Field is not present, so set it.
m.foo = 1
```
@ -395,26 +395,26 @@ else:
No presence:
```
```ruby
m = Msg.new
if m.foo != 0
// "Clear" the field:
# "Clear" the field:
m.foo = 0
else
// Default value: field may not have been present.
Joshua Haberman
3 years ago