queryx: add binding transformer

queryx.go

@@ -93,7 +93,9 @@ type Queryx struct {
 	*gocql.Query
 	Names  []string
 	Mapper *reflectx.Mapper
-	err    error
+
+	tr  Transformer
+	err error
 }
 
 // Query creates a new Queryx from gocql.Query using a default mapper.
@@ -104,9 +106,17 @@ func Query(q *gocql.Query, names []string) *Queryx {
 		Query:  q,
 		Names:  names,
 		Mapper: DefaultMapper,
+		tr:     DefaultBindTransformer,
 	}
 }
 
+// WithBindTransformer sets the query bind transformer.
+// The transformer is called right before binding a value to a named parameter.
+func (q *Queryx) WithBindTransformer(tr Transformer) *Queryx {
+	q.tr = tr
+	return q
+}
+
 // BindStruct binds query named parameters to values from arg using mapper. If
 // value cannot be found error is reported.
 func (q *Queryx) BindStruct(arg interface{}) *Queryx {
@@ -157,6 +167,10 @@ func (q *Queryx) bindStructArgs(arg0 interface{}, arg1 map[string]interface{}) (
 			arglist = append(arglist, val)
 		}
 
+		if q.tr != nil {
+			arglist[i] = q.tr(q.Names[i], arglist[i])
+		}
+
 		return nil
 	})
 
@@ -184,6 +198,10 @@ func (q *Queryx) bindMapArgs(arg map[string]interface{}) ([]interface{}, error)
 		if !ok {
 			return arglist, fmt.Errorf("could not find name %q in %#v", name, arg)
 		}
+
+		if q.tr != nil {
+			val = q.tr(name, val)
+		}
 		arglist = append(arglist, val)
 	}
 	return arglist, nil

queryx_test.go

@@ -88,6 +88,25 @@ func TestQueryxBindStruct(t *testing.T) {
 		}
 	})
 
+	t.Run("with transformer", func(t *testing.T) {
+		tr := func(name string, val interface{}) interface{} {
+			if name == "age" {
+				return 42
+			}
+			return val
+		}
+
+		names := []string{"name", "age", "first", "last"}
+		args, err := Query(nil, names).WithBindTransformer(tr).bindStructArgs(v, nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if diff := cmp.Diff(args, []interface{}{"name", 42, "first", "last"}); diff != "" {
+			t.Error("args mismatch", diff)
+		}
+	})
+
 	t.Run("error", func(t *testing.T) {
 		names := []string{"name", "age", "first", "not_found"}
 		_, err := Query(nil, names).bindStructArgs(v, nil)
@@ -111,6 +130,28 @@ func TestQueryxBindStruct(t *testing.T) {
 		}
 	})
 
+	t.Run("fallback with transformer", func(t *testing.T) {
+		tr := func(name string, val interface{}) interface{} {
+			if name == "not_found" {
+				return "map_found"
+			}
+			return val
+		}
+
+		names := []string{"name", "age", "first", "not_found"}
+		m := map[string]interface{}{
+			"not_found": "last",
+		}
+		args, err := Query(nil, names).WithBindTransformer(tr).bindStructArgs(v, m)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if diff := cmp.Diff(args, []interface{}{"name", 30, "first", "map_found"}); diff != "" {
+			t.Error("args mismatch", diff)
+		}
+	})
+
 	t.Run("fallback error", func(t *testing.T) {
 		names := []string{"name", "age", "first", "not_found", "really_not_found"}
 		m := map[string]interface{}{
@@ -143,6 +184,25 @@ func TestQueryxBindMap(t *testing.T) {
 		}
 	})
 
+	t.Run("with transformer", func(t *testing.T) {
+		tr := func(name string, val interface{}) interface{} {
+			if name == "age" {
+				return 42
+			}
+			return val
+		}
+
+		names := []string{"name", "age", "first", "last"}
+		args, err := Query(nil, names).WithBindTransformer(tr).bindMapArgs(v)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if diff := cmp.Diff(args, []interface{}{"name", 42, "first", "last"}); diff != "" {
+			t.Error("args mismatch", diff)
+		}
+	})
+
 	t.Run("error", func(t *testing.T) {
 		names := []string{"name", "first", "not_found"}
 		_, err := Query(nil, names).bindMapArgs(v)

session.go

@@ -49,6 +49,7 @@ func (s Session) ContextQuery(ctx context.Context, stmt string, names []string)
 		Query:  s.Session.Query(stmt).WithContext(ctx),
 		Names:  names,
 		Mapper: s.Mapper,
+		tr:     DefaultBindTransformer,
 	}
 }
 
@@ -62,6 +63,7 @@ func (s Session) Query(stmt string, names []string) *Queryx {
 		Query:  s.Session.Query(stmt),
 		Names:  names,
 		Mapper: s.Mapper,
+		tr:     DefaultBindTransformer,
 	}
 }
 

transformer.go

@@ -0,0 +1,13 @@
+// Copyright (C) 2017 ScyllaDB
+// Use of this source code is governed by a ALv2-style
+// license that can be found in the LICENSE file.
+
+package gocqlx
+
+// Transformer transforms the value of the named parameter to another value.
+type Transformer func(name string, val interface{}) interface{}
+
+// DefaultBindTransformer just do nothing.
+//
+// A custom transformer can always be set per Query.
+var DefaultBindTransformer Transformer