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I am trying to create a dialog box that informs the user when the input is wrong (or even when any type of error occurs) in the manipulate function.

I have the following code:

Plotter[function_] := 
Plot[function, {x, -1, 1}, PlotLabel -> Style [function, Bold]];
Manipulate[
Quiet[Plotter[f]], {{f, Sin[x], 
Text[Style["Function:", Bold, Medium]]}, {Sin[x], Tan[x]}
}, Text[Style["\nType the function:", Bold]], 
Panel[DynamicModule[{var = "Function"}, InputField[Dynamic[f]]]], 
ControlPlacement -> Left, ControlType -> PopupMenu, 
SaveDefinitions -> True, SynchronousInitialization -> False]

And I implemented the dialog box in the following way:

Plotter[function_] := 
Plot[function, {x, -1, 1}, PlotLabel -> Style [function, Bold]];
Manipulate[
Quiet[Check[Plotter[f], {MessageDialog["Error."], Abort[]}]], {{f, 
Sin[x], Text[Style["Function:", Bold, Medium]]}, {Sin[x], Tan[x]}
}, Text[Style["\nType the function:", Bold]], 
Panel[DynamicModule[{var = "Function"}, InputField[Dynamic[f]]]], 
ControlPlacement -> Left, ControlType -> PopupMenu, 
SaveDefinitions -> True, SynchronousInitialization -> False]

which seems to work up until the point when I try to type another function. The plotting does not work and the error box does not appear anymore when the input is wrong. Why does this happen? And how to I fix this? I think that the Abort[] function causes this, but if I do not put it there, the message box appears indefinitely.

I created the error with the user input "Sin[x,y]".

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Maybe this?

Plotter[function_] := Plot[function, {x, -1, 1}, PlotLabel -> Style[function, Bold]];
Manipulate[
 Quiet[(fold = f; #) &@                     (* set fold to new f if valid *)
   Check[Plotter[f],
    {MessageDialog["Error."]; f = fold}]],  (* reset invalid f *)
 {{f, Sin[x], Text[Style["Function:", Bold, Medium]]}, {Sin[x], Tan[x]}},
 {{fold, Sin[x]}, ControlType -> None},     (* keep previous valid f *)
 Text[Style["\nType the function:", Bold]], 
 Panel[DynamicModule[{var = "Function"}, InputField[Dynamic[f]]]], 
 ControlPlacement -> Left, ControlType -> PopupMenu, 
 SaveDefinitions -> True, SynchronousInitialization -> False]
Improve this answer
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