Hello all. I have problem with doing a math with using speed from gps. After start program i'm getting this error message:
What is curious all calculations are calculated and displayed correctly. The error is displayed only once after runing a program and then everything works well. However, it is irritating and I would like to deal with it somehow. I don't know if I understood the error message correctly, but it probably informs me that the variable is empty and i want to use speed to calculate when there is no any data avaible yet? If yes how to solve this issue? Becouse i don't have any more ideas to try.
Colud you help me?
These valueIfTagNotThere probably need to be either 1 or 0
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Be sure that all the values are different from empty value , also in tinyDb use another value for if tag is not there .
These value are always the same and never empty. When i take of variable from math and raplace it for random value like here:
Eeverything works perfect without any error.
When variable will be again in mathematical formula then the error will come back:
I'm sure that the problem is somewhere but i cant undarstand where exactly:
Test the value in the variable with Do It when using the companion app. You do not show in your blocks where you are running that procedure, and it could be before you set the variable?
You did not understand the purpose of the valueIfTagNotThere socket... on first run of the app TinyDB is empty, also will those default values be taken for your calculations... calculations with an empty string do not work,
therefore
use Do it to debug your blocks, see also tip 4 here App Inventor: How to Learn | Pura Vida Apps
see also Live Development, Testing, and Debugging Tools
Taifun
Trying to push the limits! Snippets, Tutorials and Extensions from Pura Vida Apps by 
Taifun.
Value of TinyDB are never empty becouse i always set them after runnig the app if it first time. Now i found a relationship that when the application is running and the GPS does not have a fix yet, the error will show up, but after the fix is found error doesn't show up. So now the question is how to build blocks which will set some constant value of the speed variable when GPS does not have a fix yet?
The error message however is telling us, that the second argument of your division is an empty string
I would use correct default values for calculations, i.e. 0 or 1, but as you like...
Again, use Do it to debug your blocks
Taifun
I like the is a number block for validating input.
There is a block is empty string to verify if a result is empty
or you can try with an empty text without the "" as you tried .
Yes this block solved the problem. Thanks
This block also will work
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