API Design: Optional Parameters

[luantranminh]

https://samwho.dev/blog/api-design-optional-parameters/

› Guiding principles

API design is hard. A good API needs to be:

1. Easy to change without breaking user code.
2. Simple for the common use-cases.
3. Easy to understand without having to read documentation.
4. Helpful when things go wrong.

› Go: adding parameters a better way

type options struct {
  followRedirects bool
  headers map[string]string
}

type Option = func(*options)

var (
  FollowRedirects = func(o *options) {
    o.followRedirects = true
  }

  Header = func(key, value string) func(*options) {
    return func(o *options) {
      o.headers[key] = value
    }
  }
)

func Get(url string, os ...Option) (Response, error) {
  o := options{}
  for _, option := range os {
    option(&o)
  }

  // ...
}

Some examples of using this:

rsp, err := http.Get("http://example.com")

If you want to specify parameters:

rsp, err := http.Get("http://example.com",
  http.FollowRedirects,
  http.Header("Accept-Encoding", "gzip"))