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https://issues.apache.org/jira/browse/LUCENENET-515?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13527639#comment-13527639
]
Christopher Currens commented on LUCENENET-515:
-----------------------------------------------
Two lines of reflection code isn't what I would consider a "whole lot of
reflection mess" to get what you want done.
{code}
public static class AttributeSourceExtensions
{
public static IAttribute GetAttribute(this AttributeSource
attributeSource, Type t)
{
if(!typeof(IAttribute).IsAssignableFrom(t))
throw new ArgumentException("Type of T must inherit from
IAttribute");
var mi =
typeof(AttributeSource).GetMethod("GetAttribute").MakeGenericMethod(t);
return (IAttribute)mi.Invoke(attributeSource, null);
}
}
{code}
You could easily do the same for {{HasAttribute}}. Here's an example:
{code}
private static void Main(string[] args)
{
string str = "This is my text";
var a = new StandardAnalyzer(Version.LUCENE_30);
var ts = a.TokenStream("Field", new StringReader(str));
ts.IncrementToken();
Console.WriteLine(ts.GetAttribute<ITermAttribute>().Term);
Console.WriteLine(((ITermAttribute)
ts.GetAttribute(typeof(ITermAttribute))).Term);
}
{code}
I'm not saying that the API shouldn't have an overload that accepts a type, in
fact I agree that it should. HOWEVER, Lucene 3.0.3 doesn't have a method like
this in java, and so that is the reason why it was removed. Keep in mind that
things run slowly around here, and so I'm not sure if or when this additional
overload will be added for 3.0.3.
> bring back TokenStream.GetAttribute(Type).
> ------------------------------------------
>
> Key: LUCENENET-515
> URL: https://issues.apache.org/jira/browse/LUCENENET-515
> Project: Lucene.Net
> Issue Type: Improvement
> Components: Lucene.Net Core
> Affects Versions: Lucene.Net 3.0.3
> Reporter: Jens Melgaard
>
> I Have noticed that TokenStream.GetAttribute(Type) is gone in favor for
> TokenStream.GetAttribute<Type>();
> Obviously TokenStream.GetAttribute<Type>() is a better syntax; but it should
> not replace TokenStream.GetAttribute(Type), but instead compliment it... But
> this is a common pitfall, especially for non-.NET developers and people who
> have not run into the implications of this..
> In the case of Lucene.NET, it is properly unlikely that this will affect
> anyone, however, I consider what has been done bad practice... now why is
> that?
> Many would think like this:
> Before I had to do this old thing...
> {code}TokenStream.GetAttribute(typeof(TermAttribute));{code}
> And god I hated that, so now I replaced it with the much more beautiful:
> {code}TokenStream.GetAttribute<TermAttribute>();{code}
> And deleted that old hag of a method taking a Type... And now I am happy...
> BUT!...
> What when...
> {code}
> Type myNotDefinedHereType = GetTypeFromSomeWhere();
> TokenSteam.GetAttribute.... ?????!?!?!?... Uhm... What now????
> {code}
> Now you have to write a whole lot of reflection mess, use a dynamically
> compiled delegate using IL-Emit or the Mono Compiler as a Service...
> All of those 3 workarounds are generally just ugly...
> If you keept both...
> {code}
> Type myNotDefinedHereType = GetTypeFromSomeWhere();
> TokenSteam.GetAttribute(myNotDefinedHereType);
> {code}
> While it might be unlikely that it will ever be used, there is always the off
> case, and API's should support both...
> So instead of:
> {code}
> public virtual T GetAttribute<T>() where T : IAttribute
> {
> Type key = typeof (T);
> if (!this.attributes.ContainsKey(key))
> throw new ArgumentException("This AttributeSource does not have the
> attribute '" + key.FullName + "'.");
> else
> return (T) this.attributes[key].Value;
> }
> {code}
> Do:
> {code}
> public T GetAttribute<T>() where T : IAttribute
> {
> return (T) GetAttribute(typeof(T));
> }
> public virtual IAttribute GetAttribute(Type key)
> {
> //Note: Since Type is required to implement IAttribute, I would
> properly check that as well to be able to provide a more meaningfull error...
> However to speed things up, I would do it inside the if bellow...
> if (!this.attributes.ContainsKey(key))
> throw new ArgumentException("This AttributeSource does not have the
> attribute '" + key.FullName + "'.");
> else
> return (T) this.attributes[key].Value;
> }
> {code}
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