Programming isn’t a simple thing, it can be very nerve-racking when you have written up a lot of code but keep getting errors that you have no idea what it means. Many Arduino users are similarly stuck on an error ‘function not declared in this scope’, which prevents their codes from calling a function. This has been reported in several forums, so we thought to help you understand what the error means and how it gets triggered.
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What Is “Arduino Error Was Not Declared In This Scope”?
Generally, to find errors in your particular code, it is required that we have a look at it to pinpoint the issue, however, if the error that you are getting is something not declared in this scope, then it is only happening due to certain parameters you have overlooked. First, I will discuss what scope is in the C language and then what can trigger it.
What Is Scope?
Variables in C based language that is used by Arduino has a property called a scope, which is basically the parameter of the variable’s visibility to other functions. There are locally declared variables and globally declared variables. Global variables can be seen by all functions and are declared outside of it, whereas the local variable is only within the scope of the function it is declared in.
The Scope is basically a parameter for the visibility of the declared variables to functions. If a variable is declared outside the scope of a function, then that function cannot call it unless it gets declared in it.
What Causes The Function Not Declared In This Scope Error?
Any error that says not declared in this scope, in both cases for:
- Function was not declared in this scope
- Variable was not declared in this scope
means that the function or variable is not declared within the scope of the function it is called in. If you are calling the values from another function, then this error can also arise when it is unable to call the value of the declared function.
How To Fix Function Not Declared In This Scope Error?
Now, there is no exact fix for this issue, but as I have mentioned above the cause is generally the same, however complex the code may be. Here are some simple things that you can keep in mind and double-check to fix this issue.
Solution 1: Check If The Function Or Variable Triggering This Issue Has Been Declared
The first thing you must do when facing this error is to check whether the function you are calling has been declared or not. If the called function is not declared, then it is not within the scope and will trigger this error.
Solution 2: Check If The Called Function Is In Private Parameter Of A Class
If you are calling a function from another class and have declared it properly but still getting this error, you need to check the class that you are calling the function from. Check if the function is under the Private parameter or Public parameter of the Class.
The functions under the Private parameter can only be used by that class and cannot be called from other functions outside its scope. Move the called function to the Public parameter and it should fix this issue.
So, there you have it. Now you know what triggers the ‘function not declared in this scope’ error in Arduino and how to fix it. If you are still facing issues finding the cause of the error in your program, try asking in the Arduino forums by pasting the part of the code triggering the issue. There are plenty of experts there that will have a look at it and pinpoint you to the issue.