v0.0.116

mongoext/projections.go

@@ -0,0 +1,30 @@
+package mongoext
+
+import (
+	"go.mongodb.org/mongo-driver/bson"
+	"reflect"
+	"strings"
+)
+
+// ProjectionFromStruct automatically generated a mongodb projection for a struct
+// This way you can pretty much always write
+// `options.FindOne().SetProjection(mongoutils.ProjectionFromStruct(...your_model...))`
+// to only get the data from mongodb that you will actually use in the later decode step
+func ProjectionFromStruct(obj interface{}) bson.M {
+	v := reflect.ValueOf(obj)
+	t := v.Type()
+
+	result := bson.M{}
+
+	for i := 0; i < v.NumField(); i++ {
+		tag := t.Field(i).Tag.Get("bson")
+		if tag == "" {
+			continue
+		}
+		tag = strings.Split(tag, ",")[0]
+
+		result[tag] = 1
+	}
+
+	return result
+}