[stringtemplate-interest] IAttributeRenderer and Type Inheritancein C#
Vincent DARON
vdaron at ask.be
Thu Oct 22 15:19:13 PDT 2009
Jonathan Buhacoff wrote:
>
> On Oct 22, 2009, at 12:23 PM, Vincent DARON wrote:
>
>
>> I'm quite new to StringTemplate, the first need for that feature was
>> internationalization of Enumerations
>>
>
> I know you're not using Java... In Java this is easy with
> ResourceBundle. Find or make the equivalent in your platform ; this
> doesn't require a modification to StringTemplate.
Resources exists in .NET as well, this is not the problem here. using
typeof(Enum) allow the creation of ONE AttributeRenderer for ALL the
Enum used in my attributes.
>
>> (All Types starting with "My" are custom classes here to ease reading)
>>
>> I simply try to do
>>
>> StringTemplate.SetAttributeRenderer(typeof(Enum),new
>> MyI18nEnumRenderer());
>>
>> It did'nt works and I had to do
>>
>> StringTemplate.SetAttributeRenderer(typeof(MyEnum1),new
>> MyI18nEnumRenderer());
>> StringTemplate.SetAttributeRenderer(typeof(MyEnum2),new
>> MyI18nEnumRenderer());
>> StringTemplate.SetAttributeRenderer(typeof(MyEnum3),new
>> MyI18nEnumRenderer());
>> ...
>>
>> The second need for that feature was for Formatting purposes
>>
>> StringTemplate.SetAttributeRenderer(typeof(IFormatProvider),new
>> MyFormatProviderRenderer());
>>
>
> You can create a new type MyFormattedType that implements your
> IFormatProvider interface. Then register
> your MyFormatProviderRenderer renderer for MyFormattedType. Then wrap
> all your types that implement IFormatProvider with a MyFormattedType
> type object. That will do what you want, and after you set it up once
> it's easy to reuse.
>
This is maybe specific to .NET as well, IFormattable for example, is an
interface that is implemented by all the basic types (int, string,
Datetime , ...) to specify what is the formatting to use when calling
the method ToString().
When I'm using StringTemplate, I'm using Graph objects as Attributes :
class Address{
public string Street;
public int Number;
...
}
class Person{
public string Name;
public Address Address;
}
in my template there are plenty of call to $Person.Name$ or
$Person.Address.Street$
It's not possible to wrap all types that implement IFormatProvider (wrap
"int" or "string" ?)
>
>> did'nt works either...
>>
>> It's after that second problem that I looked into Sources and propose
>> my approach.
>>
>> I do not think that it could be a speed problem, with a behavior like
>> mine, people using AttributeRenderer will probably use less Renderer.
>> The problem about priority is a little more embarrassing. Maybe using
>> 2 lists instead of a Dictionary (Type and Renderer) ? People are
>> adding AttributeRenderer in the order they will be processed.
>
> No, people are adding AttributeRenderers in any order because they go
> in a map and the order doesn't matter. Only the interface renderers
> would have to go in an ordered list. And in that case it's easier to
> provide an ordered List to ST with all your interface renderers
> already in it than to duplicate a list implementation in ST with add,
> remove, insertAt, etc. methods.
Users of StringTemplate shouldn't be aware that it's a map behind ;-).
But you're right, using a list may break the code of some people.
>
>>
>> StringTemplate st = new ...
>>
>> st.SetAttributeRenderer(typeof(MyClass), new MyRenderer());
>> st.SetAttributeRenderer(typeof(IMyInterface), new MyIRenderer());
>> st.SetAttributeRenderer(typeof(object), new MyDefaultRenderer());
>>
>> st.ToString();
>>
>
> I wouldn't mix the class and interface renderers; already mentioned
> the reasons in my last post.
>
>> In this example the MyDefaultRenderer will be called for all
>> Attributes that are not of type MyClass and do not implements
>> IMyInterface. It look quite intuitive to me. The only difference is
>> that the order of Setting Renderer matters.
>
> I think a better way, which you can do right now, is for you to
> subclass StringTemplate and override setAttribute to automatically
> wrap your objects that implement a specific interface with a class for
> which you register a renderer. You can handle or ignore priority
> issues and it won't require a change to StringTemplate.
Again, it's not possible to wrap object graph easily.
It seems that my proposition is maybe too much .NET oriented.
Thanks for answers and precisions.
Vincent
>
>>
>> It's only suggestion :-) and any other ideas to solve these
>> "problems" are welcome.
>>
>
>
>
>> Thanks,
>>
>> Vincent
>>
>> PS: Accessing source from trunk is possible ? How ?
>>
>>
>>
>>
>> Jonathan Buhacoff wrote:
>>> If it's integrated with the class renderers as I showed in my diff,
>>> there's a little extra work to do. On the other hand, most classes
>>> only implement handful of interfaces, and since this code doesn't do
>>> any string processing it will probably be fast enough.
>>>
>>> Or, if it's implemented as a separate map of renderers, then it will
>>> only slow down processing if the programmer has registered any
>>> interface renderers. But that seems a little messy to me, maybe more
>>> messy than the speed savings is worth.
>>>
>>> Finally, the other issue with interface renderers is priority - as
>>> proposed now, we have no control over which renderer will be found
>>> first, and if a class implements more than one interface with a
>>> registered renderer, the output will be non-deterministic. I think
>>> that's a bad thing.
>>>
>>> The way to control that would be to have a complete interface to
>>> manage the priority of interface renderers, or to have ST implement
>>> something like
>>> registerInterfaceAttributeRenderers(List<AttributeRenderer>
>>> renderers); so the programmer can specify the order of the
>>> renderers.
>>>
>>> So the loop would change to iterating through the registered interface
>>> renderers and checking if the value implements each one (and they
>>> would be in priority order).
>>>
>>> That makes things deterministic again, and would require the use of a
>>> list of interface renders separate from the map of class renderers,
>>> which means only people who use interface renderers would incur any
>>> performance penalty.
>>>
>>> I'm still trying to think of a case where this scheme would be better
>>> than wrapping everything with an adapter and registering a renderer
>>> for that, because automatically wrapping certain classes that
>>> implement an interface automatically is so easy to do by subclassing
>>> StringTemplate. I'm still thinking along the lines of
>>> internationalization, units of measure, stuff like that. Vincent can
>>> you provide a real world case?
>>>
>>>
>>> On Oct 22, 2009, at 9:45 AM, Sam Harwell wrote:
>>>
>>>
>>>> Hi Vincent,
>>>>
>>>> My first thought is this changes an O(1) algorithm that has to run for
>>>> every rendered item into an O(n) algorithm. I would have to run this
>>>> through the instrumenting profiler to make sure it isn't slowing down
>>>> the rendering process before I could include it. There are a few other
>>>> ways to approach the problem, but I'm not yet sure which one would
>>>> work
>>>> out best.
>>>>
>>>> Sam
>>>>
>>>> -----Original Message-----
>>>> From: stringtemplate-interest-bounces at antlr.org
>>>> [mailto:stringtemplate-interest-bounces at antlr.org] On Behalf Of
>>>> Vincent
>>>> DARON
>>>> Sent: Thursday, October 22, 2009 10:12 AM
>>>> To: stringtemplate-interest at antlr.org
>>>> Subject: [stringtemplate-interest] IAttributeRenderer and Type
>>>> Inheritancein C#
>>>>
>>>> Hi
>>>>
>>>> I would like to be able to register an IAttributeRenderer for objects
>>>> implementing an Interface.
>>>>
>>>> Part of current implementation of GetAttributeRenderer
>>>>
>>>> public virtual IAttributeRenderer GetAttributeRenderer( Type
>>>> attributeClassType )
>>>> {
>>>> IAttributeRenderer renderer = null;
>>>> if ( _attributeRenderers != null )
>>>> {
>>>> if ( !_attributeRenderers.TryGetValue(
>>>> attributeClassType, out renderer ) )
>>>> renderer = null;
>>>> }
>>>> // ...snip ... //
>>>> }
>>>>
>>>>
>>>> My proposal (untested, but should be ok)
>>>>
>>>> public virtual IAttributeRenderer GetAttributeRenderer( Type
>>>> attributeClassType )
>>>> {
>>>> IAttributeRenderer renderer = null;
>>>> if ( _attributeRenderers != null )
>>>> {
>>>> foreach(Type key in _attributeRenderers.Keys)
>>>> {
>>>> if(key.IsAssignableFrom(attributeClassType))
>>>> {
>>>> renderer = _attributeRenderers[key];
>>>> break;
>>>> }
>>>> }
>>>> }
>>>> // ...snip ... //
>>>> }
>>>>
>>>>
>>>> It will allow to register Attribute Renderer for objects implementing
>>>> interfaces
>>>>
>>>> RegisterAttributeRenderer(typeof(IFormatProvider), ...);
>>>>
>>>> Goot idea ?
>>>>
>>>> Second question, is it possible to have access to source using Source
>>>> Control (Subversion, Hg, Git, ...) ? It would be far easier to test
>>>> and
>>>> create patches.
>>>>
>>>> Thanks for answer/comments
>>>>
>>>> Vincent
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>>>
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>>
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