I am getting bitten by the type assertion related error in the below the code snippet. I am not sure what I am missing. I am doing type assertions in the following places itr = itr.(*DbIterator).Iterator and key := itr.Key().(*Key).Slice and value := itr.Value().(*Value).Slice. I am wondering if there is a better way to do this without type assertions everywhere in the code base or better design patterns to handle this kind of scenario. The code snippet is part of a larger code base. I have pulled the most relevant bits for this question. Any help in this regard is much appreciated.
package rocksdb
import (
"github.com/tecbot/gorocksdb"
)
func (s *RocksDB) GetCFIterator(cfHandler *gorocksdb.ColumnFamilyHandle) db.Iterator {
opt := gorocksdb.NewDefaultReadOptions()
opt.SetFillCache(true)
defer opt.Destroy()
return &DbIterator{s.DB.NewIteratorCF(opt, cfHandler)}
}
type DbIterator struct {
*gorocksdb.Iterator
}
type Key struct {
*gorocksdb.Slice
}
type Value struct {
*gorocksdb.Slice
}
func (iterator *DbIterator) Key() db.Keyer {
return &Key{iterator.Iterator.Key()}
}
func (iterator *DbIterator) Value() db.Valuer {
return &Value{iterator.Iterator.Value()}
}
type RocksDB struct {
DB *gorocksdb.DB
}
I have an interator interface
package db
import (
"bytes"
"testing"
)
type Iterator interface {
Valid() bool
Next()
Close()
SeekToFirst()
SeekToLast()
Seek(key []byte)
Key() Keyer
Value() Valuer
}
type Keyer interface {
}
type Valuer interface {
}
func testIterator(t *testing.T, itr db.Iterator, expectedValues map[string][]byte) {
itrResults := make(map[string][]byte)
itr = itr.(*DbIterator).Iterator //Line 270 which the error throws
itr.SeekToFirst()
for ; itr.Valid(); itr.Next() {
key := itr.Key().(*Key).Slice
value := itr.Value().(*Value).Slice
k := makeCopy(key.Data())
v := makeCopy(value.Data())
itrResults[string(k)] = v
}
if len(itrResults) != len(expectedValues) {
t.Fatalf("Expected [%d] results from iterator, found [%d]", len(expectedValues), len(itrResults))
}
for k, v := range expectedValues {
if !bytes.Equal(itrResults[k], v) {
t.Fatalf("Wrong value for key [%s]. Expected [%s], found [%s]", k, itrResults[k], v)
}
}
}
Error Message
github.com/hyperledger/fabric/core/db/rocksdb
core/db/rocksdb/rocksdb_test.go:270: cannot use itr.(*DbIterator).Iterator (type *gorocksdb.Iterator) as type db.Iterator in assignment:
*gorocksdb.Iterator does not implement db.Iterator (wrong type for Key method)
have Key() *gorocksdb.Slice
want Key() db.Keyer