goext/reflectext/mapAccess.go

99 lines
2.4 KiB
Go
Raw Normal View History

2024-01-12 18:40:29 +01:00
package reflectext
import (
"reflect"
"strings"
)
// GetMapPath returns the value deep inside a hierahically nested map structure
// eg:
// x := langext.H{"K1": langext.H{"K2": 665}}
// GetMapPath[int](x, "K1.K2") == 665
func GetMapPath[TData any](mapval any, path string) (TData, bool) {
var ok bool
split := strings.Split(path, ".")
for i, key := range split {
if i < len(split)-1 {
mapval, ok = GetMapField[any](mapval, key)
if !ok {
return *new(TData), false
}
} else {
return GetMapField[TData](mapval, key)
}
}
return *new(TData), false
}
// GetMapField gets the value of a map, without knowing the actual types (mapval is any)
// eg:
// x := langext.H{"K1": 665}
// GetMapPath[int](x, "K1") == 665
//
// works with aliased types and autom. dereferences pointes
func GetMapField[TData any, TKey comparable](mapval any, key TKey) (TData, bool) {
rval := reflect.ValueOf(mapval)
for rval.Kind() == reflect.Ptr && !rval.IsNil() {
rval = rval.Elem()
}
if rval.Kind() != reflect.Map {
return *new(TData), false // mapval is not a map
}
kval := reflect.ValueOf(key)
if !kval.Type().AssignableTo(rval.Type().Key()) {
return *new(TData), false // key cannot index mapval
}
eval := rval.MapIndex(kval)
if !eval.IsValid() {
return *new(TData), false // key does not exist in mapval
}
destType := reflect.TypeOf(new(TData)).Elem()
if eval.Type() == destType {
return eval.Interface().(TData), true
}
if eval.CanConvert(destType) && !preventConvert(eval.Type(), destType) {
return eval.Convert(destType).Interface().(TData), true
}
if (eval.Kind() == reflect.Ptr || eval.Kind() == reflect.Interface) && eval.IsNil() && destType.Kind() == reflect.Ptr {
return *new(TData), false // special case: mapval[key] is nil
}
for (eval.Kind() == reflect.Ptr || eval.Kind() == reflect.Interface) && !eval.IsNil() {
eval = eval.Elem()
if eval.Type() == destType {
return eval.Interface().(TData), true
}
if eval.CanConvert(destType) && !preventConvert(eval.Type(), destType) {
return eval.Convert(destType).Interface().(TData), true
}
}
return *new(TData), false // mapval[key] is not of type TData
}
func preventConvert(t1 reflect.Type, t2 reflect.Type) bool {
if t1.Kind() == reflect.String && t1.Kind() != reflect.String {
return true
}
if t2.Kind() == reflect.String && t1.Kind() != reflect.String {
return true
}
return false
}