best way to check for empty pipe when returning value

[ziggy]

Hi, I've got to ask what may be a simple question.  When doing a Gremlin query, I want to check to see if the pipe is empty before returning a value.  Is there a simple way to check for an empty pipe and return a pre-specified value if it's empty?  I must be missing something

# can't do this if the pipe empties out before it hits the next()

output = v1.inE('LINKTYPE').outV().next().name

# return value or null if pipe empty (what a mess and it fails in some cases)

output=null; v1.inE('LINKTYPE').outV().sideEffect{output=it.name?it.name:null}

# this works, but even more ugly

nodes=[]; v1.inE('LINKTYPE').outV().fill(nodes)

output = (nodes.size > 0)?nodes[0].name:null 

# something like this would be ideal

output = v1.inE('LINKTYPE').outV().nextValOrElse('name', 'MISSING')

thanks for reading this

[Daniel Kuppitz]

Simply do this:

pipe = v1.in('LINKTYPE')[0].name

output = pipe.hasNext() ? pipe.next() : null

Cheers,

Daniel

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[Louis Clark]

much better, thanks Daniel.

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[Andras Gefferth]

+1 for the question and +1 for the answer!
Always wanted to know, but was afraid to ask :)

[Mike Oxford]

Simply do this:

pipe = v1.in('LINKTYPE')[0].name
output = pipe.hasNext() ? pipe.next() : null

Why does this not work?

v1.in('LINKTYPE')[0].name.hasNext() ? pipe.next() : null

Does hasNext() have some kind of syntactic sugar to detect that it's being called off of a null object and automatically return false?

[Daniel Kuppitz]

Why does this not work?
v1.in('LINKTYPE')[0].name.hasNext() ? pipe.next() : null

Because you don't even define the pipe object in your snippet.

Anyway, maybe it's worth to mention that you can do this in TP3: v1.in('LINKTYPE').limit(0).values("name").tryNext().orElse(null)

Cheers,

Daniel

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[Nick De Young]

Trynextorelse 

Looks like scala !!

Sent from my iPhone

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