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package arg
import (
"encoding"
"fmt"
"reflect"
"strconv"
"time"
)
// set a value from a string
func setScalar(v reflect.Value, s string) error {
if !v.CanSet() {
return fmt.Errorf("field is not exported")
}
// If we have a nil pointer then allocate a new object
if v.Kind() == reflect.Ptr && v.IsNil() {
v.Set(reflect.New(v.Type().Elem()))
}
// Get the object as an interface
scalar := v.Interface()
// If it implements encoding.TextUnmarshaler then use that
if scalar, ok := scalar.(encoding.TextUnmarshaler); ok {
return scalar.UnmarshalText([]byte(s))
}
// If we have a pointer then dereference it
if v.Kind() == reflect.Ptr {
v = v.Elem()
}
// Switch on concrete type
switch scalar.(type) {
case time.Duration:
x, err := time.ParseDuration(s)
if err != nil {
return err
}
v.Set(reflect.ValueOf(x))
return nil
}
// Switch on kind so that we can handle derived types
switch v.Kind() {
case reflect.String:
v.SetString(s)
case reflect.Bool:
x, err := strconv.ParseBool(s)
if err != nil {
return err
}
v.SetBool(x)
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
x, err := strconv.ParseInt(s, 10, v.Type().Bits())
if err != nil {
return err
}
v.SetInt(x)
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
x, err := strconv.ParseUint(s, 10, v.Type().Bits())
if err != nil {
return err
}
v.SetUint(x)
case reflect.Float32, reflect.Float64:
x, err := strconv.ParseFloat(s, v.Type().Bits())
if err != nil {
return err
}
v.SetFloat(x)
default:
return fmt.Errorf("cannot parse argument into %s", v.Type().String())
}
return nil
}
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