Feature request #17928

Need a way to distinguish between outputs from more than one use of the same algorithm when building a model.

Added by Alister Hood about 6 years ago. Updated about 6 years ago.

Assignee:Victor Olaya
Pull Request or Patch supplied:No Resolution:invalid
Easy fix?:No Copied to github as #:25824


If you use the same algorithm more than once in a model, as far as I can tell there is no way to tell the difference between the outputs of each, for use in other algorithms in the model.

In general you can just select one of the outputs and see where the connecting arrows are drawn, but this doesn't help if you are using the outputs as input to an algorithm which take multiple inputs (e.g. perhaps you are smoothing several rasters before using them in another algorithm). If they are separate inputs then you will be able to figure it out with some messing around, because the list of available inputs is sorted. But if they are chosen through the multiple input widget then in master it is possible to drag and drop to change the order, after which you would not be able to tell which one is which.

You might expect to be able to work around this by naming the outputs (i.e. as "final results"), but the names of final results aren't used in the list of input layers.

Perhaps the most user friendly way to solve this would be to separate the "name" from the status as a "final result".
i.e. have a checkbox for "final result", and also allow to specify a name (whether or not it is a final result), and use the name to select it in subsequent algorithms in the model.
That would solve this problem without creating unnecessary final results (i.e. specify a name and don't check "final result"), and would also be nice because you could use the name of a "final result" if you are also using it in another algorithm.

  • Hopefully I am wrong, but if so, it is easy to miss, because I saw people on Stackexchange complaining about the same thing...


#1 Updated by Nyall Dawson about 6 years ago

  • Resolution set to invalid
  • Status changed from Open to Closed

You can rename the child algorithm in the model - change the "Description" value after double clicking the algorithm. This description is used when listing the outputs and allows them to be distinguished.

#2 Updated by Alister Hood about 6 years ago

Of course, thanks.
I'd interpreted "description" as being for documenting why you are doing something, rather than giving it a unique identifier!
Is it the best wording? Maybe it is worth adding something like this to the user manual (section: graphical modeller>definition of the workflow):

Tip: edit the "Description" field in the algorithm parameters dialog
The description is used when listing the outputs and allows them to be distinguished if your model uses the same algorithm more than once.

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