How to create multiple validation methods for one endpoint? - json

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.