Method HGet

structure/hash.go:159–216

HGet gets the string value of a hash field. It takes a string key 'k' and a field 'f', and returns the corresponding value and any possible error. Parameters: k: The key of the hash table. f: The field name. Returns: interface{}: The value corresponding to the field, or nil if the field doesn

(key string, field interface{})

// - The retrieved byte data is converted back to the corresponding data type.
// - Returns the value corresponding to the field and any possible error.
func (hs *HashStructure) HGet(key string, field interface{}) (interface{}, error) {
	// check the key ttl
	ttl, _ := hs.TTL(key)
	if ttl == -1 {
		return nil, _const.ErrKeyIsExpired
	}

	// Convert the parameters to bytes
	k := stringToBytesWithKey(key)

	// Convert the parameters to bytes
	f, err, _ := interfaceToBytes(field)
	if err != nil {
		return nil, err
	}

	// Check the parameters
	if len(k) == 0 || len(f) == 0 {
		return nil, _const.ErrKeyIsEmpty
	}

	// Find the hash metadata by the given key
	hashMeta, err := hs.findHashMeta(key, Hash)
	if err != nil {
		return nil, err
	}

	// If the counter is 0, return nil
	if hashMeta.counter == 0 {
		return nil, nil
	}

	// Create a new HashField
	hf := &HashField{
		field:   f,
		key:     k,
		version: hashMeta.version,
	}

	// Encode the HashField
	hfBuf := hf.encodeHashField()

	// Get the field from the database
	value, err := hs.db.Get(hfBuf)
	if err != nil {
		return nil, err
	}

	// Get the value type from the hashValueTypes
	valueType := hs.hashValueType

	// Values of different types need to be converted to corresponding types
	valueToInterface, err := byteToInterface(value, valueType)
	if err != nil {
		return nil, err
	}
	return valueToInterface, nil
}