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Christopher Smith commented on TINKERPOP-2502:
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Putting on my API-client hat, "that's your job!"
My thinking is going like this: The purpose of an interface is to support
multiple implementations. Imagine we have a {{TraversalStartSteps}} interface
defining our quad.
- {{GraphTraversal implements TraversalStartSteps}} by simply doing the exact
thing it already does, appending the new {{AddVertexStep}} to an ongoing
traversal.
- {{__.start()}} returns a {{GraphTraversal}}, so it's covered.
- {{GraphTraversalSource implements TraversalStartSteps}} by doing the same
thing it already does, which is to clone stuff _and add the "start steps"
necessary to get it going_.
As far as I can tell, by introducing {{TraversalStartSteps}}, client code can
now initiate calling whichever of them regardless of whether they're initiating
a blank traversal, appending to an existing one, or starting an anonymous
subtraversal, and I don't think any further modification to any of the existing
API is required, only creating this minimal superinterface.
> Consistent start API for anonymous and regular traversals
> ---------------------------------------------------------
>
> Key: TINKERPOP-2502
> URL: https://issues.apache.org/jira/browse/TINKERPOP-2502
> Project: TinkerPop
> Issue Type: Improvement
> Components: process
> Affects Versions: 3.4.9
> Reporter: Christopher Smith
> Priority: Minor
>
> I am writing a graph-based application and am taking advantage of the
> method-based nature of Gremlin to librarify some of my common usage patterns.
> However, I'm encountering a frustrating problem where I frequently need to be
> able to attach the same traversal steps to either a real
> {{GraphTraversalSource}} or an anonymous traversal (usually for some nested
> reason like a coalesced conditional insert).
> The methods on {{__}} are mostly static, but I can call {{__.start()}} to
> obtain a live {{GraphTraversal}} object and then proceed from there (invoking
> {{GraphTraversal#addV}}, for example). {{GraphTraversalSource}}, however,
> requires me to invoke the method {{GraphTraversalSource#addV}} to get
> started, and there's no common base type. I think I could theoretically use
> something like {{inject()}}, but that seems particularly odd.
> It would be helpful to either have both {{GraphTraversal}} and
> {{GraphTraversalSource}} implement a common interface holding the "start
> opcodes" or to have a {{GraphTraversalSource#start()}} method that could be
> used to obtain a "blank" traversal.
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