Generic method for retrieving list of models (structs)

I'm trying to create basic CRUD for my service. It is based on data models created in structs. The problem is that I really dont want to repeat code for CRUD methods. For example I have ModelA and ModelB defined as structs:

type ModelA struct {
	ID              bson.ObjectId     `json:"ID,omitempty" bson:"_id,omitempty"`
	Slug            string            `json:"slug" bson:"slug,omitempty"`
	Creator         string            `json:"-" bson:"creator,omitempty"`
	DefaultLanguage string            `json:"defaultLanguage" bson:"defaultLanguage,omitempty"`
}

type ModelB struct {
	ID              bson.ObjectId     `json:"ID,omitempty" bson:"_id,omitempty"`
	Type            string            `json:"type" bson:"type,omitempty"`
}

What I want is to make generic method which retrieves an array of given model. It is important for me to use models. I can do it quick with pure interface{} types but will loose model functionality, for example hiding some properties in JSON output (ex. ModelA.Creator).

So far I've created generic methods for creating new data and retrieving single model. Here is example code:

// GET: /modelsa/{:slug}
func (r *Routes) GetModelA(w rest.ResponseWriter, req *rest.Request) {
    // set model as ModelA
	var model models.ModelA
	r.GetBySlug(w, req, &model, "models")
}

// GET: /modelsb/{:slug}
func (r *Routes) GetModelB(w rest.ResponseWriter, req *rest.Request) {
    // set model as ModelB
    var model models.ModelB
    r.GetBySlug(w, req, &model, "models")
}

func (r *Routes) GetBySlug(w rest.ResponseWriter, req *rest.Request, m interface{}, collection string) {
	slug := req.PathParam("slug")

	if err := r.GetDocumentBySlug(slug, collection, m, w, req); err != nil {
		rest.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	w.WriteJson(m)
}

GetModelA and GetModelB are route handlers which uses generic method GetBySlug that returns a JSON formatted by given model.

I want to do the same but with the array of given models. So far I ve got problem to cast the result into the struct:

// GET /modelsa/
func (r *Routes) GetModels(w rest.ResponseWriter, req *rest.Request) {
    // I think in this case I don't have to pass an array of struct
    // because the given struct is only reference. It could be:
    // var result models.ModelA as well. Converting it into array could 
    // be done in GetList() method
	var result []models.ModelA
	r.GetList(w, req, &result, "models")
}

func (r *Routes) GetList(w rest.ResponseWriter, req *rest.Request, res interface{}, col string) {

}

I cant set res argument as an array of interface{}. Also I if i try to cast result to the []interface{} within GetList() method, I cant then cast it to the res argument as it is not an array.

Is there a nice way to do this? Maybe I think wrong and should redesign the methods? Any advice would be appreciated.

You can declare new types which represent slice of your models. For example,

type ModelAList []ModelA
type ModelBList []ModelB

Then when you pass variables of these new types into your r.GetDocumentBySlug(), the functions in the encoding/json package will unmarshal the slices accordingly.

You can find working examples here (marshaling) and here (unmarshaling).