[Engine-devel] [engine-devel] frontend builders proposal

[Tal Nisan]

Makes the frontend code much more readable, great job!

Tal.


On 01/26/2013 10:58 PM, Eli Mesika wrote:
>
> ----- Original Message -----
>> From: "Tomas Jelinek"<tjelinek at redhat.com>
>> To: engine-devel at ovirt.org
>> Sent: Friday, January 25, 2013 11:55:43 AM
>> Subject: [Engine-devel] [engine-devel] frontend builders proposal
>>
>> Hi All,
>>
>> as many of you may know, the way how the frontend and backend models
>> are built on frontend (uicommonweb project) is not really ideal.
>> Currently this logic is copy pasted over and over again to different
>> places where it is needed with minor changes to fulfill the specific
>> requirements. It is not only aesthetically problematic, but I recall
>> tons of bugs caused by introducing a new field and forgetting to add
>> it to every place it is used in GUI.
>>
>> Now, as there will be big changes in the VM/Template models
>> (http://www.ovirt.org/Features/Instance_Types), so the way how the
>> VM, Template, Pool and also the newly created Instance Types models
>> are being built has to be touched anyhow, it is a great opportunity
>> to rethink the way how we do it.
>>
>> I have created a simple infrastructure
>> (http://gerrit.ovirt.org/#/c/10874/) which could be used for it, and
>> a PoC patch which uses this infrastructure
>> (http://gerrit.ovirt.org/#/c/11354/). Please note that the PoC is
>> not really impressive in means of removing duplications, I wanted to
>> start with the simplest possibility.
>>
>> The principles behind the infrastructure:
>> - have small, well named, easy to understand and reuse builders
>> - this builders can be chained together or embedded to each other to
>> build the full resulting object (composite pattern)
>> - this builders can be asynchronous, and the next builder in the
>> chain has to be executed only when the current is completely done
>>
>> The structure:
>> - the base is an interface called Builder which has a method
>> build(source, destination, rest)
>> - the builder implementing this interface
>>    + will get the source and destination objects
>>    + copies whatever he wants from source to destination
>>    + when done, executes build on the first element of the rest
>>      + this may sound awkward, but this is the way how the async calls
>>      can be "linearized" in a general way, not embedding anonymous
>>      class into anonymous
>>        class into anonymous class... as we do it today.
>>      + for synchronous builders, there is a BaseSyncBuilder which
>>      takes care of this boilerplate calling of next and exposes a
>>      simple method
>>        build(S source, D destination)
>>    + to simplify the creating and running the chain of builders, there
>>    is a BuilderExecutor class (can be created as sync or async)
>>
>> So, a simple example - even more simple than the PoC patch :)
>>
>> //create the first builder
>> class FirstLetterBuilder extends BaseSyncBuilder<String,
>> StringBuilder>  {
>>   @Override
>>   protected void build(String source, StringBuilder destination) {
>>       // copy the first letter to the destination
>>       destination.append(source.charAt(0));
>>   }
>> }
>>
>> //create the second builder
>> class SecondLetterBuilder extends BaseSyncBuilder<String,
>> StringBuilder>  {
>>   @Override
>>   protected void build(String source, StringBuilder destination) {
>>       // copy the second letter to the destination
>>       destination.append(source.charAt(1));
>>   }
>> }
>>
>> // usage
>> ...
>> // create the destination object
>> StringBuilder res = new StringBuilder();
>>
>> // configure the executor with the two builders
>> BuilderExecutor<String, StringBuilder>  executor = new
>> BuilderExecutor<String, StringBuilder>(
>>          new FirstLetterBuilder(),
>>          new SecondLetterBuilder()
>>          );
>>
>> // execute the builder chain ("ab" is the source, res the
>> destination)
>> executor.build("ab", res);
>>
>> // use the result
>> ...
>>
>> That's it. And the nice part is, that this FirstLetterBuilder and
>> SecondLetterBuilder can be reused anywhere or combined with any
>> other builders.
>>
>> Any comments on this will be more than welcome!
> great and really simplifies work and eliminate bugs resulted from copy/past code
> gave +1
> Thanks
> Eli
>> Thank you,
>> Tomas
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