These are AppHandlers from a pattern I found online while researching gorilla/mux. They part of a struct that satisfies http.Handler. If you notice, the following two blocks are exactly the same. Effectively, they could be passed the 'variant' ("flow" or "process") as a string.
func CreateFlow(a *AppContext, w http.ResponseWriter, r *http.Request) (int, error) {
highest, code, err := a.Create("flow", r)
if code != 200 || err != nil {
return code, err
}
b := new(bytes.Buffer)
json.NewEncoder(b).Encode(struct {
Highest int `json:"id"`
}{highest})
w.Header().Set("Content-Type", "application/json")
w.Write(b.Bytes())
return 200, nil
}
func CreateProcess(a *AppContext, w http.ResponseWriter, r *http.Request) (int, error) {
highest, code, err := a.Create("process", r)
if code != 200 || err != nil {
return code, err
}
b := new(bytes.Buffer)
json.NewEncoder(b).Encode(struct {
Highest int `json:"id"`
}{highest})
w.Header().Set("Content-Type", "application/json")
w.Write(b.Bytes())
return 200, nil
}
However, the following two blocks not only need the string, but they need a variable of the associated type ("Flow" and "Process") to successfully Unmarshal the hit I get from ElasticSearch. Other than that, they are Identical code.
func GetFlow(a *AppContext, w http.ResponseWriter, r *http.Request) (int, error) {
hit, code, err := a.GetByID("flow", mux.Vars(r)["id"], r)
if code != 200 {
return code, err
}
var flow Flow
err = json.Unmarshal(*hit.Source, &flow)
if err != nil {
return 500, err
}
flow.ESID = hit.Id
b := new(bytes.Buffer)
json.NewEncoder(b).Encode(flow)
w.Header().Set("Content-Type", "application/json")
w.Write(b.Bytes())
return 200, nil
}
func GetProcess(a *AppContext, w http.ResponseWriter, r *http.Request) (int, error) {
hit, code, err := a.GetByID("process", mux.Vars(r)["id"], r)
if code != 200 {
return code, err
}
var process Process
err = json.Unmarshal(*hit.Source, &process)
if err != nil {
return 500, err
}
process.ESID = hit.Id
b := new(bytes.Buffer)
json.NewEncoder(b).Encode(process)
w.Header().Set("Content-Type", "application/json")
w.Write(b.Bytes())
return 200, nil
}
I am not sure how to generalize this behavior in golang when there is a declared type involved. These handlers are all in the same package too, as I think that they are all accomplishing a similar task. I am very clearly repeating myself in code but I need advice on how I can improve. I've gone past "a little copying is better than a little dependency." but I am afraid because "reflection is never clear".
Here is an example of the declaration in main using one of these functions.
api.Handle("/flow/{id:[0-9]+}", handlers.AppHandler{context, handlers.GetFlow}).Methods("GET")