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package indexers
import (
"fmt"
"reflect"
)
// MethodIndexer is used to create an index based on a string returned
// as a result of calling a method on the object.
// It is assumed that the method has no arguments.
type MethodIndexer struct {
// Method name to call to get the string to bulid the index on.
Method string
}
// FromObject take Obj and returns index key formed using
// the fields.
func (s *MethodIndexer) FromObject(obj interface{}) (bool, []byte, error) {
v := reflect.ValueOf(obj)
key := ""
method := v.MethodByName(s.Method)
resp := method.Call(nil)
if len(resp) != 1 {
return false, nil, fmt.Errorf("function call returned unexpected result")
}
key = resp[0].String()
if key == "" {
return false, nil, nil
}
return true, []byte(key), nil
}
// FromArgs takes in a string and returns its byte form.
func (s *MethodIndexer) FromArgs(args ...interface{}) ([]byte, error) {
blob := ""
for _, arg := range args {
s, ok := arg.(string)
if !ok {
return nil, fmt.Errorf("argument must be a string: %#v", arg)
}
blob += s
}
if blob == "" {
return nil, fmt.Errorf("empty args is not a valid value")
}
return []byte(blob), nil
}
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