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From "Simon Svensson (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (LUCENENET-515) bring back TokenStream.GetAttribute(Type).
Date Wed, 12 Dec 2012 08:07:22 GMT

     [ https://issues.apache.org/jira/browse/LUCENENET-515?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Simon Svensson resolved LUCENENET-515.
--------------------------------------

       Resolution: Fixed
    Fix Version/s: Lucene.Net 3.6

This should be fixed in revision 1420558, in trunk.
                
> 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
>             Fix For: Lucene.Net 3.6
>
>
> 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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