如何为一个端点创建多种验证方法？

Question

I want to make a validation api in order to validate a set of json requests regarding specific set of rules. To do that I want to use just one endpoint and call functions that correspond to the specific json struct. I know that there is no method overloading in go so I am kind of stumped.

...

type requestBodyA struct {
    SomeField   string `json:"someField"`
    SomeOtherField  string `json:"someOtherField"`
}

type requestBodyB struct {
    SomeDifferentField   string `json:"someDifferentField"`
    SomeOtherDifferentField  string `json:"someOtherDifferentField"`
}



type ValidationService interface {
    ValidateRequest(ctx context.Context, s string) (err error)
}

type basicValidationService struct{}

...

So in order to validate lots of different json requests, is it better to create structs for each and every json request? Or should I create these dynamically? How can I know what kind of request is sent if I only have one endpoint?

Answer 1

If you have a single endpoint/rpc that has to accept different JSON types, you'll need to tell it how to distinguish between them, somehow. One option is to have something like:

type request struct {
  bodyA *requestBodyA
  bodyB *requestBodyB
}

Then, populate these fields in a container JSON object appropriately. The json module will only populate bodyA if a bodyA key is present, otherwise leaving it a nil, and so on.

Here's a more complete example:

type RequestBodyFoo struct {
    Name    string
    Balance float64
}

type RequestBodyBar struct {
    Id  int
    Ref int
}

type Request struct {
    Foo *RequestBodyFoo
    Bar *RequestBodyBar
}

func (r *Request) Show() {
    if r.Foo != nil {
        fmt.Println("Request has Foo:", *r.Foo)
    }
    if r.Bar != nil {
        fmt.Println("Request has Bar:", *r.Bar)
    }
}

func main() {
    bb := []byte(`
    {
        "Foo": {"Name": "joe", "balance": 4591.25}
    }
    `)

    var req Request
    if err := json.Unmarshal(bb, &req); err != nil {
        panic(err)
    }
    req.Show()

    var req2 Request
    bb = []byte(`
    {
        "Bar": {"Id": 128992, "Ref": 801472}
    }
    `)
    if err := json.Unmarshal(bb, &req2); err != nil {
        panic(err)
    }
    req2.Show()
}

Another option is to do it more dynamically with maps, but it's likely that the method above will be sufficient.