Dear Openforis Team In my survey new trees shall get an automatically generated ID (1, 2, 3...). For this I created a Number Attribute field and checked "Calculated". How do I define the Expression so that the ID always rises +1. Thanks for your help, Sabrina

asked 09 Apr '19, 09:59

Sabrina's gravatar image

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Hi Sabrina,

checked as "Calculated" it is not necessary. In "Default Value" you have to write Expression


where: "tree" is Entity name "tree_id" is Number attribute name

best regards beka

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answered 09 Apr '19, 11:13

beka's gravatar image

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Dear Sabrina,
In the default values section, you can define default values with conditions; you can define 2 items with this parameters:

  1. Constant: 100 - Apply if: count(parent()/tree) = 1
  2. Expression: math:max(parent()/tree/tree_num) + 1

The items defined in the default values section work like this: Collect iterates over the items defined there and when it finds an item that verifies the condition defined in the "Apply if" expression, it calculates the value to apply using the Constant field or the Expression field. If you don't specify any expression in the "Apply if" field, it means "always true" (this is why you can leave it empty only for the last item, otherwise the other items won't ever be evaluated).

Open Foris Team

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answered 18 Apr '19, 11:03

OF%20Collect's gravatar image

OF Collect ♦♦
accept rate: 23%

Thanks Beka, that helped. Is it also possible that the numbering of the ID starts at 100? For example 101, 102...

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answered 18 Apr '19, 10:13

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question asked: 09 Apr '19, 09:59

question was seen: 862 times

last updated: 18 Apr '19, 11:03