protobuf/csharp/src/ProtocolBuffers/Reflection/IFieldAccessor.cs

#region Copyright notice and license
// Protocol Buffers - Google's data interchange format
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#endregion

namespace Google.Protobuf.Reflection
{
    /// <summary>
    /// Allows fields to be reflectively accessed.
    /// </summary>
    public interface IFieldAccessor
    {
        /// <summary>
        /// Returns the descriptor associated with this field.
        /// </summary>
        FieldDescriptor Descriptor { get; }

        // TODO: Should the argument type for these messages by IReflectedMessage?

        /// <summary>
        /// Clears the field in the specified message. (For repeated fields,
        /// this clears the list.)
        /// </summary>
        void Clear(object message);

        /// <summary>
        /// Fetches the field value. For repeated values, this will be an
        /// <see cref="IList"/> implementation. For map values, this will be an
        /// <see cref="IDictionary"/> implementation.
        /// </summary>
        object GetValue(object message);

        /// <summary>
        /// Mutator for single "simple" fields only.
        /// </summary>
        /// <remarks>
        /// Repeated fields are mutated by fetching the value and manipulating it as a list.
        /// Map fields are mutated by fetching the value and manipulating it as a dictionary.
        /// </remarks>
        /// <exception cref="InvalidOperationException">The field is not a "simple" field, or the message is frozen.</exception>
        void SetValue(object message, object value);
    }
}