How can I save and retrieve a map into redis using redigo? - go

Question

I have a map like this, which I want to save/retrive from redis using redigo:
animals := map[string]bool{
"cat": true,
"dog": false,
"fox": true,
}
The length of the map may vary.
I tried these function:
func SetHash(key string, value map[string]bool) error {
conn := Pool.Get()
defer conn.Close()
_, err := conn.Do("HMSET", key, value)
if err != nil {
return fmt.Errorf("error setting key %s to %s: %v", key, value, err)
}
return err
}
func GetHash(key string) (map[string]bool, error) {
conn := Pool.Get()
defer conn.Close()
val, err := conn.Do("HGETALL", key)
if err != nil {
fmt.Errorf("error setting key %s to %s: %v", key, nil, err)
return nil, err
}
return val, err
}
But can not make GetHash correctly. I've checked the docs examples and it was not helpful. So appreciate your help to have a working example.

Answer 1

HMSET is deprecated, use HSET instead, no effect here though.
The map[string]bool may be flattened with AddFlat() for SetHash().
c.Do("HSET", redis.Args{}.Add("key").AddFlat(value)...)
For GetHash(), use Values(). You may use ScanStruct() to map to a struct or loop through the values to create a map dynamically.
v, err := redis.Values(c.Do("HGETALL", key))
redis.ScanStruct(v, &myStruct);
See example from redigo tests in scan_test.go.

Answer 2

The application is responsible for converting structured types to and from the types understood by Redis.
Flatten the map into a list of arguments:
func SetHash(key string, value map[string]bool) error {
conn := Pool.Get()
defer conn.Close()
// Create arguments: key field value [field value]...
var args = []interface{}{key}
for k, v := range value {
args = append(args, k, v)
}
_, err := conn.Do("HMSET", args...)
if err != nil {
return fmt.Errorf("error setting key %s to %v: %v", key, value, err)
}
return err
}
Convert the returned field value pairs to a map:
func GetHash(key string) (map[string]bool, error) {
conn := Pool.Get()
defer conn.Close()
values, err := redis.Strings(conn.Do("HGETALL", key))
if err != nil {
return nil, err
}
// Loop through [field value]... and parse value as bool.
m := map[string]bool{}
for i := 0; i < len(values); i += 2 {
b, err := strconv.ParseBool(value)
if err != nil {
return nil, errors.New("value not a bool")
}
m[key] = b
}
return m, nil
}