Add callback mechanism and implement on-decode callback

mongox/query/callbacks.go

@@ -0,0 +1,7 @@
+package query
+
+import (
+	"context"
+)
+
+type OnDecode func(ctx context.Context, iter interface{}) (err error)

mongox/query/compose.go

@@ -38,6 +38,7 @@ func Push(q *Query, f interface{}) (ok bool) {
 	ok = ok || applySkip(q, f)
 	ok = ok || applyProtection(q, f)
 	ok = ok || applyPreloader(q, f)
+	ok = ok || applyCallbacks(q, f)
 
 	return ok
 }
@@ -123,3 +124,14 @@ func applyPreloader(q *Query, f interface{}) (ok bool) {
 
 	return false
 }
+
+func applyCallbacks(q *Query, f interface{}) (ok bool) {
+
+	switch cb := f.(type) {
+	case OnDecode:
+		q.ondecode = append(q.ondecode, cb)
+		ok = true
+	}
+
+	return
+}

mongox/query/query.go

@@ -11,6 +11,7 @@ type Query struct {
 	sorter    Sorter
 	skipper   Skipper
 	preloader Preloader
+	ondecode  []OnDecode
 }
 
 // And function pushes the elem query to the $and array of the query
@@ -75,6 +76,11 @@ func (q *Query) Preloader() (ok bool, preloads []string) {
 	return
 }
 
+// OnDecode callback is called after the mongo decode function
+func (q *Query) OnDecode() (callbacks []OnDecode) {
+	return q.ondecode
+}
+
 // Empty checks the query for any content
 func (q *Query) Empty() (isEmpty bool) {
 	return len(q.m) == 0