FPC message: Wrong number of parameters specified

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Missing parameter or too many parameters

You confused the function and forgot a parameter or added a parameter too much.

Missing @

For example:

Button1.Click := Button1Click;

In {$mode objfpc} you must add the @-address-operator to tell the compiler, that you want the pointer to the function, not the result of the function:

Button1.Click := @Button1Click;

Delphi users often confuse this, because Delphi allows it and adds the @ internally. If you prefer the Delphi syntax you can use {$mode Delphi} instead of {$mode ObjFPC}, or use the mode switch {$modeswitch classicprocvars on}.