[patterns-discussion] About the Collecting Parameter pattern

[Jesús Alonso]

Thanks for your help. I understand a little better this pattern.

About the book, can't have access to it right now, and I would have to buy 
it for just that pattern...

Thanks again for your help


>Hi,
>
>this pattern solves the problem of how a series of operations can all 
>contribute to a collection of results. You could of course have the 
>operations return a collection and accumulate the results in the loop that 
>calls them, but in e.g. Java methods can have only one return value and 
>that may be "in use" for other things.
>
>A typical use is the gathering of messages, especially error messages. The 
>return value of the operations is often in use for the actual "business" 
>part of the operations, and the use of exceptions would mean that every 
>operation can contribute at most one message.
>
>Therefore: pass a collection to each operation so that it can contribute 
>all the messages. This parameter "collects" the messages, hence the name of 
>the pattern. It is useful e.g. for collecting messages to be displayed in a 
>UI.
>
>It is documented in Kent Beck's "Smalltalk Best Practices" book, wich 
>contains a lot of very helpful patterns that are applicable to other 
>languages as well.
>
>- Arno
>
>
>
>Jesús Alonso wrote:
>>Hello.
>>
>>I need information about the Collecting Parameter design pattern, but all 
>>I could find was the info in this page: 
>>http://c2.com/cgi/wiki?CollectingParameter
>>
>>The fact is that the information given there about the pattern isn't 
>>enough for me to understand very well the pattern.
>>I would find helpful any information about what this pattern does exactly, 
>>some examples, and maybe a concrete context where it could be applied 
>>successfully and why.
>>
>>Thanks in advance.
>>
>>Best regards,
>>  Jesús Alonso
>>
>>
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>
>