[Qgis-user] Problem using Model Inputs variable in an Select by expression in the model Designer

[Nicolas Cadieux]

Hi,
Does anyone have an idea?

Nicolas Cadieux
https://gitlab.com/njacadieux

> Le 8 juill. 2021 à 01:17, Nicolas Cadieux <njacadieux.gitlab at gmail.com> a écrit :
> 
> 
> Hi,
> 
> I am creating a model that fixes Network files before they are used in the QGIS Network analysis (Shortest path) tools.
> 
> This is my work flow:
> 
> Create a "Length" field (value) and calculate $length in the field calculator
> Split the Multipart lines into Singlepart lines
> Create a "Length2" field (value) and calculate $length in the field calculator
> Select by expression Length != Length2.  This basically gives me a selection of line that have been modified by the Multipart to Singlepart algorithm. (I get 8 results)
> This works well
> 
> The problem is when I create and Input String to let the user create a "Length" field.  This become a variable called @NamelengthField. My work flow become:
> 
> User input "Length" in the Model input. (@NamelengthField)
> Create a "Length" field using  @NamelengthField (as pre-calculated value) and calculate $length in the field calculator: This is OK
> Split the Multipart lines into Singlepart lines: This is OK
> Create a "Length2" field using  @NamelengthField ||'2'  (as pre-calculated value) and calculate $length in the field calculator: This is OK this field (Length2) is created and calculated properly. 
> I get stuck  when I try Select by expression using  @NamelengthField != @NamelengthField || '2' (as pre-calculated value) (I get all lines back) and the test does not work.
> I tried stuff like
> 
> @NamelengthField != (@NamelengthField || '2')
> 
> '@NamelengthField != @NamelengthField || '2''
> 
> "@NamelengthField != @NamelengthField || '2'"
> 
> "@NamelengthField"|| !=|| "@NamelengthField || '2'"
> 
> Even simple @NamelengthField = 5.286365157529550 (which should extract exactly one value).  
> 
> Any ideas?
> 
> Nicolas
> 
> QGIS 3.18.2 on Windows 10 
> 
> 
> 
> 
> 
> 
> 
> -- 
> Nicolas Cadieux
> https://gitlab.com/njacadieux
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