simonepri commented on a change in pull request #12393:
URL: https://github.com/apache/beam/pull/12393#discussion_r462453993
##########
File path: sdks/go/pkg/beam/create.go
##########
@@ -34,31 +34,44 @@ func Create(s Scope, values ...interface{}) PCollection {
}
// CreateList inserts a fixed set of values into the pipeline from a slice or
-// array. It is a convenience wrapper over Create.
+// array. Unlike Create this supports the creation of an empty PCollection.
func CreateList(s Scope, list interface{}) PCollection {
- var ret []interface{}
val := reflect.ValueOf(list)
if val.Kind() != reflect.Slice && val.Kind() != reflect.Array {
panic(fmt.Sprintf("Input %v must be a slice or array", list))
}
+ var ret []interface{}
for i := 0; i < val.Len(); i++ {
ret = append(ret, val.Index(i).Interface())
}
- return Must(TryCreate(s, ret...))
+ var t reflect.Type
+ if len(ret) == 0 {
+ t = reflect.TypeOf(list).Elem()
+ } else {
+ t = reflect.ValueOf(ret[0]).Type()
+ }
+ return Must(TryCreateList(s, ret, t))
}
func addCreateCtx(err error, s Scope) error {
return errors.WithContextf(err, "inserting Create in scope %s", s)
}
-// TryCreate inserts a fixed set of values into the pipeline. The values must
-// be of the same type.
+// TryCreate inserts a fixed non-empty set of values into the pipeline. The
+// values must be of the same type.
func TryCreate(s Scope, values ...interface{}) (PCollection, error) {
if len(values) == 0 {
return PCollection{}, addCreateCtx(errors.New("create has no
values"), s)
}
t := reflect.ValueOf(values[0]).Type()
+ return TryCreateList(s, values, t)
+}
+
+// TryCreateList inserts a fixed set of values into the pipeline from a slice
or
+// array. The values must be of the same type. Unlike TryCreate this supports
+// the creation of an empty PCollection.
+func TryCreateList(s Scope, values []interface{}, t reflect.Type)
(PCollection, error) {
Review comment:
Thanks for the comment!
I did not know about this convention, but makes completely sense.
Let me know if it is okay now.
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