// setInterfaceValue sets an interface value to a concrete value through
// reflection.  If the concrete value does not implement the interface, the
// setting will panic.  This routine turns the panic into an error return.
// This dance avoids manually checking that the value satisfies the
// interface.
// TODO(rsc): avoid panic+recover after fixing issue 327.
func setInterfaceValue(ivalue *reflect.InterfaceValue, value reflect.Value) {
	defer func() {
		if e := recover(); e != nil {
			error(e.(os.Error))
		}
	}()
	ivalue.Set(value)
}
Example #2
0
// encodeInterface encodes the interface value iv.
// To send an interface, we send a string identifying the concrete type, followed
// by the type identifier (which might require defining that type right now), followed
// by the concrete value.  A nil value gets sent as the empty string for the name,
// followed by no value.
func (enc *Encoder) encodeInterface(b *bytes.Buffer, iv *reflect.InterfaceValue) {
	state := enc.newEncoderState(b)
	state.fieldnum = -1
	state.sendZero = true
	if iv.IsNil() {
		state.encodeUint(0)
		return
	}

	ut := userType(iv.Elem().Type())
	name, ok := concreteTypeToName[ut.base]
	if !ok {
		errorf("gob: type not registered for interface: %s", ut.base)
	}
	// Send the name.
	state.encodeUint(uint64(len(name)))
	_, err := state.b.WriteString(name)
	if err != nil {
		error(err)
	}
	// Define the type id if necessary.
	enc.sendTypeDescriptor(enc.writer(), state, ut)
	// Send the type id.
	enc.sendTypeId(state, ut)
	// Encode the value into a new buffer.  Any nested type definitions
	// should be written to b, before the encoded value.
	enc.pushWriter(b)
	data := new(bytes.Buffer)
	enc.encode(data, iv.Elem(), ut)
	if enc.err != nil {
		error(enc.err)
	}
	enc.popWriter()
	enc.writeMessage(b, data)
	if enc.err != nil {
		error(err)
	}
	enc.freeEncoderState(state)
}