micro/examples/client/codegen/README.md

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# Code Generation [Experimental]
We're experimenting with code generation to reduce the amount of boiler plate code written.
## Example
Going from this
```golang
req := client.NewRequest("go.micro.srv.example", "Example.Call", &example.Request{
Name: "John",
})
rsp := &example.Response{}
if err := client.Call(context.Background(), req, rsp); err != nil {
return err
}
```
To
```golang
rsp, err := cl.Call(context.Background(), &example.Request{Name: "John"})
if err != nil {
return err
}
```
## Generation of stub code for the example service
```shell
go get github.com/micro/protobuf/protoc-gen-go
cd examples/server/proto/example
protoc --go_out=plugins=micro:. example.proto
```
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Look at examples/server/proto/example/example.pb.go
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to see the generated code.
## Guide
### Download the protoc-gen-go code
```shell
go get github.com/micro/protobuf/protoc-gen-go
```
### Define your proto service.
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hello.proto
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```shell
syntax = "proto3";
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// package name is used as the service name for discovery
// if service name is not passed in when initialising the
// client
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package go.micro.srv.greeter;
service Say {
rpc Hello(Request) returns (Response) {}
}
message Request {
optional string name = 1;
}
message Response {
optional string msg = 1;
}
```
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**Note: Remember to set package name in the proto, it's used to generate
the service for discovery.**
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### Generate code
```shell
protoc --go_out=plugins=micro:. hello.proto
```
### Generated code
```shell
// Client API for Say service
type SayClient interface {
Hello(ctx context.Context, in *Request) (*Response, error)
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}
type sayClient struct {
c client.Client
serviceName string
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}
func NewSayClient(serviceName string, c client.Client) SayClient {
if c == nil {
c = client.NewClient()
}
if len(serviceName) == 0 {
serviceName = "go.micro.srv.greeter"
}
return &sayClient{
c: c,
serviceName: serviceName,
}
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}
func (c *sayClient) Hello(ctx context.Context, in *Request) (*Response, error) {
req := c.c.NewRequest(c.serviceName, "Say.Hello", in)
out := new(Response)
err := c.c.Call(ctx, req, out)
if err != nil {
return nil, err
}
return out, nil
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}
// Server API for Say service
type SayHandler interface {
Hello(context.Context, *Request, *Response) error
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}
func RegisterSayHandler(s server.Server, hdlr SayHandler) {
s.Handle(s.NewHandler(hdlr))
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}
```
### Use the client
```golang
import (
"fmt"
"golang.org/x/net/context"
"github.com/micro/go-micro/client"
hello "path/to/hello/proto"
)
func main() {
cl := hello.NewSayClient("go.micro.srv.greeter", client.DefaultClient)
// alternative initialisation
// cl := hello.NewSayClient("", nil)
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rsp, err := cl.Hello(contex.Background(), &hello.Request{"Name": "John"})
if err != nil {
fmt.Println(err)
}
}
```