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From andyhot <andy...@di.uoa.gr>
Subject Re: T5: default binding is prop even in template
Date Wed, 17 Jan 2007 16:10:04 GMT

Kent Tong wrote:
> Howard Lewis Ship <hlship <at> gmail.com> writes:
>
>   
>> I haven't gotten a lot of feedback ... Kent is very opposed to the
>> idea.  Jesse and a few others are for it. I think it will be neat.
>>     

When Tapestry 4 was in development, I had voted for having default binding
prefixes for each parameter.

Now... let's just say i'm not sure any more - which explains my late reply.

So, since i don't yet have a preference, let me throw in this:

How about sidestepping the issue by either
-) making parameter names (somehow) imply the binding prefix.
-) having one-letter uppercased aliases for each prefix

I don't really see much future in the first, but the second is 
interesting...


>
> Here I'd like to explain why I am opposed to it. The supposed major
> benefit of using default binding prefix is DRY. Why DRY? If there
> is code duplication and for some reason I change this code, then I 
> will have to change some other code. This is bad for maintenance.
> Now, let's return to the issue. Consider the following example:
>
>    <input type="text" t:type="TextField" value="prop:name"/>
>
> The thinking behind default prefix is that there is linkage between 
> TextField+value and prop. However, let's consider changing TextField to 
> something else say PropertySelection, do we need to change prop? No. 
> What if we need to change the parameter? There is seldom such need at 
> all. What if we need to change from prop to say an imaginary ognl 
> prefix, do we need to change TextField or value? No.
>
> As you can see above, there is absolutely no ripple effect of changes. 
> Therefore, this code is not violating DRY. So, what is the real benefit 
> of default prefix? The only benefit is saving some typing for the programmer 
> writing the code and less text to read for the programmer reading the code. 
> What is the cost? As Ron said, it is the extra step in the mental process 
> of a programmer writing or reading the code: "What is the default prefix 
> here?". Obviously, mental process is the bottle neck in programming, not 
> finger or eye ball movements.
>
> --
> Author of a book for learning Tapestry (http://www.agileskills2.org/EWDT)
>
>
>
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>
>   


-- 
Andreas Andreou - andyhot@apache.org - http://andyhot.di.uoa.gr
Tapestry / Tacos developer
Open Source / J2EE Consulting 


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