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moby--moby/libnetwork/options/options.go
allencloud 9f415d0cdb use grep to find a/an misuse
Signed-off-by: allencloud <allen.sun@daocloud.io>
2016-06-03 16:35:33 +08:00

88 lines
2.6 KiB
Go

// Package options provides a way to pass unstructured sets of options to a
// component expecting a strongly-typed configuration structure.
package options
import (
"fmt"
"reflect"
)
// NoSuchFieldError is the error returned when the generic parameters hold a
// value for a field absent from the destination structure.
type NoSuchFieldError struct {
Field string
Type string
}
func (e NoSuchFieldError) Error() string {
return fmt.Sprintf("no field %q in type %q", e.Field, e.Type)
}
// CannotSetFieldError is the error returned when the generic parameters hold a
// value for a field that cannot be set in the destination structure.
type CannotSetFieldError struct {
Field string
Type string
}
func (e CannotSetFieldError) Error() string {
return fmt.Sprintf("cannot set field %q of type %q", e.Field, e.Type)
}
// TypeMismatchError is the error returned when the type of the generic value
// for a field mismatches the type of the destination structure.
type TypeMismatchError struct {
Field string
ExpectType string
ActualType string
}
func (e TypeMismatchError) Error() string {
return fmt.Sprintf("type mismatch, field %s require type %v, actual type %v", e.Field, e.ExpectType, e.ActualType)
}
// Generic is a basic type to store arbitrary settings.
type Generic map[string]interface{}
// NewGeneric returns a new Generic instance.
func NewGeneric() Generic {
return make(Generic)
}
// GenerateFromModel takes the generic options, and tries to build a new
// instance of the model's type by matching keys from the generic options to
// fields in the model.
//
// The return value is of the same type than the model (including a potential
// pointer qualifier).
func GenerateFromModel(options Generic, model interface{}) (interface{}, error) {
modType := reflect.TypeOf(model)
// If the model is of pointer type, we need to dereference for New.
resType := reflect.TypeOf(model)
if modType.Kind() == reflect.Ptr {
resType = resType.Elem()
}
// Populate the result structure with the generic layout content.
res := reflect.New(resType)
for name, value := range options {
field := res.Elem().FieldByName(name)
if !field.IsValid() {
return nil, NoSuchFieldError{name, resType.String()}
}
if !field.CanSet() {
return nil, CannotSetFieldError{name, resType.String()}
}
if reflect.TypeOf(value) != field.Type() {
return nil, TypeMismatchError{name, field.Type().String(), reflect.TypeOf(value).String()}
}
field.Set(reflect.ValueOf(value))
}
// If the model is not of pointer type, return content of the result.
if modType.Kind() == reflect.Ptr {
return res.Interface(), nil
}
return res.Elem().Interface(), nil
}