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typemapper.go
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/
typemapper.go
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package typemapper
import (
"fmt"
"reflect"
)
// TypeFromValue returns a type value from v (being a string or string pointer)
// by using map m to determine it's enum value.
func TypeFromValue[E any](v interface{}, m map[string]E) (E, error) {
var empty E
// if v is nil, an empty value is returned.
if v == nil {
return empty, nil
}
key := toString(v)
// if v is a pointer to nil key is an empty string in which case an empty value is returned.
if key == "" {
return empty, nil
}
if v, ok := m[key]; ok {
return v, nil
}
// If v has a key set but still does not find anything, return an error.
return empty, fmt.Errorf("unknown key %s", key)
}
func toString(v interface{}) string {
var out string
if reflect.ValueOf(v).Kind() == reflect.Ptr {
if v == nil || v.(*string) == nil {
return ""
}
out = *v.(*string)
} else {
out = v.(string)
}
return out
}