Let me write it out front
Golang When building structures in , You need to create... Through optional parameters , How do we design a flexible API To initialize the structure .
Let's pass the following code snippet , Step by step, the flexibility based on the optional parameter mode is explained API How to design .
flexible API Create structure description
v1 edition
as follows Client It's a Client's sdk Structure , Yes host and port Two parameters , Our general usage is as follows ：
package client
type Client struct {
host string
port int
}
// NewClient By passing parameters
func NewClient(host string, port int) *Client {
return &Client{
host: host,
port: port,
}
}
func (c *Client) Call() error {
// todo ...
return nil
}
We can see through host and port Two parameters can create a client Of sdk.
The code that is invoked is typically as follows ：
package main import (
"client"
"log"
) func main() {
cli := client.NewClient("localhost", 1122)
if err := cli.Call(); err != nil {
log.Fatal(err)
}
}
And then one day ,sdk Made an upgrade , Several new parameters have been added , Such as timeout Timeout time ,maxConn maximum connection , retry Retry count ...
v2 edition
sdk Medium Client To define and create a structure API Change to the following ：
package client
import "time"
type Client struct {
host string
port int
timeout time.Duration
maxConn int
retry int
}
// NewClient By passing parameters
func NewClient(host string, port int) *Client {
return &Client{
host: host,
port: port,
timeout: time.Second,
maxConn: 1,
retry: 0,
}
}
// NewClient adopt 3 Parameter creation
func NewClientWithTimeout(host string, port int, timeout time.Duration) *Client {
return &Client{
host: host,
port: port,
timeout: timeout,
maxConn: 1,
retry: 0,
}
}
// NewClient adopt 4 Parameter creation
func NewClientWithTimeoutAndMaxConn(host string, port int, timeout time.Duration, maxConn int) *Client {
return &Client{
host: host,
port: port,
timeout: timeout,
maxConn: maxConn,
retry: 0,
}
}
// NewClient adopt 5 Parameter creation
func NewClientWithTimeoutAndMaxConnAndRetry(host string, port int, timeout time.Duration, maxConn int, retry int) *Client {
return &Client{
host: host,
port: port,
timeout: timeout,
maxConn: maxConn,
retry: retry,
}
}
func (c *Client) Call() error {
// todo ...
return nil
}
Through the above creation API We found that creating Client All at once NewClientWithTimeout/NewClientWithTimeoutAndMaxConn/NewClientWithTimeoutAndMaxConnAndRetry...
We can see through host and port And other parameters can create a client Of sdk.
The code that is invoked is typically as follows ：
package main import (
"client"
"log"
"time"
) func main() {
cli := client.NewClientWithTimeoutAndMaxConnAndRetry("localhost", 1122, time.Second, 1, 0)
if err := cli.Call(); err != nil {
log.Fatal(err)
}
}
This is the time , We found that v2 Version of API The definition is very unfriendly , The number of parameter combinations is also very large .
v3 edition
We need to refactor the parameters , Is it possible to merge configuration parameters into one structure ？
good , Let's put the parameters into Config in ,Client Define a cfg member
package client
import "time"
type Client struct {
cfg Config
}
type Config struct {
Host string
Port int
Timeout time.Duration
MaxConn int
Retry int
}
func NewClient(cfg Config) *Client {
return &Client{
cfg: cfg,
}
}
func (c *Client) Call() error {
// todo ...
return nil
}We can see that by defining Config Parameter can create a client Of sdk.
The code that is invoked is typically as follows ：
package main import (
"client"
"log"
"time"
) func main() {
cli := client.NewClient(client.Config{
Host: "localhost",
Port: 1122,
Timeout: time.Second,
MaxConn: 1,
Retry: 0})
if err := cli.Call(); err != nil {
log.Fatal(err)
}
}
Here we find new problems ,Config All configured members should start with uppercase , It can only be used when it is open to the public , But as a sdk, We generally do not recommend exporting these members .
What should we do ？
v4 edition
We return to the original definition ,Client Or that one? Client, There are many configuration member variables , We use the optional parameter mode to sdk refactoring .
The code after refactoring is as follows
package client
import "time"
type Client struct {
host string
port int
timeout time.Duration
maxConn int
retry int
}
// Create... With optional parameters
func NewClient(opts ...func(client *Client)) *Client {
// Create an empty Client
cli := &Client{}
// Call the optional parameter functions one by one , Copy the parameters of each function configuration to cli in
for _, opt := range opts {
opt(cli)
}
return cli
}
// hold host Parameters , Pass to function parameters c *Client
func WithHost(host string) func(*Client) {
return func(c *Client) {
c.host = host
}
}
func WithPort(port int) func(*Client) {
return func(c *Client) {
c.port = port
}
}
func WithTimeout(timeout time.Duration) func(*Client) {
return func(c *Client) {
c.timeout = timeout
}
}
func WithMaxConn(maxConn int) func(*Client) {
return func(c *Client) {
c.maxConn = maxConn
}
}
func WithRetry(retry int) func(*Client) {
return func(c *Client) {
c.retry = retry
}
}
func (c *Client) Call() error {
// todo ...
return nil
}
We can choose parameters freely , Create a client Of sdk.
The code that is invoked is typically as follows ：
package main import (
"client"
"log"
"time"
) func main() {
cli := client.NewClient(
client.WithHost("localhost"),
client.WithPort(1122),
client.WithMaxConn(1),
client.WithTimeout(time.Second))
if err := cli.Call(); err != nil {
log.Fatal(err)
}
}
From the code you call, you can see , our sdk The definition becomes flexible and beautiful .
Open source best practices
Finally, let's look at the best practice projects in this way .
gRpc
grpc.Dial(endpoint, opts...) // Dial creates a client connection to the given target.
func Dial(target string, opts ...DialOption) (*ClientConn, error) {
return DialContext(context.Background(), target, opts...)
} func DialContext(ctx context.Context, target string, opts ...DialOption) (conn *ClientConn, err error) {
cc := &ClientConn{
target: target,
csMgr: &connectivityStateManager{},
conns: make(map[*addrConn]struct{}),
dopts: defaultDialOptions(),
blockingpicker: newPickerWrapper(),
czData: new(channelzData),
firstResolveEvent: grpcsync.NewEvent(),
} for _, opt := range opts {
opt.apply(&cc.dopts)
}
// ...
}
End .
Have fun ~
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