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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* Content before git sha 34fdeebefcbf183ed7f916f931aa0586fdaa1b40
* Copyright (c) 2016, The Gocql authors,
* provided under the BSD-3-Clause License.
* See the NOTICE file distributed with this work for additional information.
*/
package gocql_test
import (
"context"
"fmt"
"log"
gocql "github.com/gocql/gocql"
)
// MyUDTUnmarshaler implements UDTUnmarshaler.
type MyUDTUnmarshaler struct {
fieldA string
fieldB int32
}
// UnmarshalUDT unmarshals the field identified by name into MyUDTUnmarshaler.
func (m *MyUDTUnmarshaler) UnmarshalUDT(name string, info gocql.TypeInfo, data []byte) error {
switch name {
case "field_a":
return gocql.Unmarshal(info, data, &m.fieldA)
case "field_b":
return gocql.Unmarshal(info, data, &m.fieldB)
default:
// If you want to be strict and return error un unknown field, you can do so here instead.
// Returning nil will ignore unknown fields, which might be handy if you want
// to be forward-compatible when a new field is added to the UDT.
return nil
}
}
// ExampleUDTUnmarshaler demonstrates how to implement a UDTUnmarshaler.
func ExampleUDTUnmarshaler() {
/* The example assumes the following CQL was used to setup the keyspace:
create keyspace example with replication = { 'class' : 'SimpleStrategy', 'replication_factor' : 1 };
create type example.my_udt (field_a text, field_b int);
create table example.my_udt_table(pk int, value frozen<my_udt>, PRIMARY KEY(pk));
insert into example.my_udt_table (pk, value) values (1, {field_a: 'a value', field_b: 42});
*/
cluster := gocql.NewCluster("localhost:9042")
cluster.Keyspace = "example"
cluster.ProtoVersion = 4
session, err := cluster.CreateSession()
if err != nil {
log.Fatal(err)
}
defer session.Close()
ctx := context.Background()
var value MyUDTUnmarshaler
err = session.Query("SELECT value FROM example.my_udt_table WHERE pk = 1").WithContext(ctx).Scan(&value)
if err != nil {
log.Fatal(err)
}
fmt.Println(value.fieldA)
fmt.Println(value.fieldB)
// a value
// 42
}
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