How to solve “The Right Side of the Equal Operator Must Be a Constant Value” in Power Apps

When working with Power Apps, you might encounter the error message: “The right side of the equal operator must be a constant value.” This can be a bit perplexing, especially if you’re new to Power Apps.

In this blog post, we’ll explore what this error means, why it occurs, and how to resolve it. 

Let’s break down this Power Apps formula step by step, focusing on the use of the ThisRecord function: 

FarmLookup

  • This part sets a variable called FarmLookup.
  • It uses the LookUp function to find a record in the Farms table where the ‘Farm ID‘ matches the specified GUID.
  • The result is stored in FarmLookup

_Farm_and_organicfields

  • This part sets another variable called _Farm_and_organicfields
  • It uses the ForAll function to iterate over a filtered set of records from the FarmandOrganicFields table.
  • The Filter function is used to select records where the Farm.’Farm ID’ matches the FarmLookup.’Farm ID’.
  • For each record in the filtered set, it creates a new record with: 
    • pfx_jsonpolygon: The JSON Polygon value from the Fields table where ‘Field (pfx_fieldid)’ matches the current record’s ‘Field (pfx_fieldid)’. Here, ThisRecord refers to the current record being processed in the ForAll loop. 
    • pfx_field: A string “Field”. 

In summary, this formula is used to:

  • Look up a specific farm by its ID and store it in FarmLookup
  • Filter the FarmandOrganicFields table to find records related to this farm. 
  • For each of these filtered records, look up additional information using ThisRecord to reference the current record in the loop, and store it in _Farm_and_organicfields

Understanding the error

In Power Apps, the equal operator (=) is used to compare values. However, the platform requires that the value on the right side of the equal operator be a constant. This means you cannot use dynamic or variable values directly in certain contexts, such as within a Filter or Lookup function. 

This will trigger the error because ThisRecord.’Field (pfx_fieldid) is not a constant value. 

Why does this happen?

Power Apps enforces this rule to ensure that the comparison is clear and unambiguous. When the right side of the equal operator is a constant, Power Apps can optimize the query and improve performance. This constraint also helps prevent logical errors that might arise from using dynamic values incorrectly. 

ThisRecord is a contextual reference that works well in simple scenarios. However, in more complex formulas, especially those involving nested functions, Power Apps may struggle to resolve ThisRecord correctly. 

How to resolve the error

To fix this error, you need to ensure that the right side of the equal operator is a constant value.

  • Use the “As” Operator: Using As operator ensures that the reference to the record is treated as a constant value within the scope of the ForAll function, for example:

This approach clarifies which data source you’re referencing, helping to avoid the common issue of ThisRecord not being evaluated as a constant within a ForAll loop in the context of a LookUp function.

Conclusion

Encountering the “right side of the equal operator must be a constant value” error in Power Apps can be frustrating, but it’s a safeguard to ensure your app runs efficiently and correctly. By understanding why this error occurs and how to resolve it, you can create more robust and performant Power Apps solutions.

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