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Twincat compare a FB with interface

In my project, I've developed FB_Modes that allow me to perform certain actions depending on the mode. These FBs implement the same I_Mode interface.

To check which mode is active, I'd like to compare the current I_Mode with an FB, but Twincat doesn't allow direct comparison between an FB and an interface. I'd like to be able to do something like this.

IF fbMachine.itfActualMode = fbMode2 THEN
    <Do something>
END_IF

Is there a way to do this? Or another way to directly compare FBs with the interface with the address.

To get around this problem, I use a unique property for each FB. But I use STRING comparison and I think this solution is not clean.

IF fbMachine.itfActualMode.sName = fbMode2.sName THEN
    <Do something>
END_IF
Solution

  • One solution is to add a method Equals() to the I_Mode and then implement it in the function blocks. Idea is to create a temporary interface and then compare if they match.

    METHOD Equals : BOOL
VAR_INPUT
    Compare : I_Mode;
END_VAR
VAR
    Temp : I_Mode;
END_VAR

//Code starts
Temp := THIS^;

Equals := Compare = Temp;

    Then you can check if the FB is equal to the interface like this

    IF fbMachine.itfActualMode.Equals(fbMode2) THEN
    //...
END_IF

    This only checks if the instances match. So it doesn't compare types, as the Guiorgy's answer does.