How to Avoid NewtApp "Please Insert the Card" Errors

One of the Newton 2.x OS Q&As
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This document was exported on 7/23/97.

How to Avoid NewtApp "Please Insert the Card" Errors (5/10/96)

Q: If a NewtApp-based application is on a PC card and the card is removed, the user gets the following error message:

"The package <package name> still needs the card you removed. Please insert it now, or information on the card may be damaged."

How can I avoid this problem?

A: While a card is unmounting, if an object on the card is still referenced, then the user will get the above error message asking them to reinsert the card. For more information about issues for applications running from a PC card see the article "The Newton Still Needs the Card You Removed"

The newtApplication method NewtInstallScript is normally called in the part's InstallScript function. One thing the NewtInstallScript does is register the viewDefs in the NewtApp base view allViewDefs slot using the global function RegisterViewDef.

Currently, RegisterViewDef requires that the data definition symbol be internal. If the symbol is on the card, then when the NewtRemoveScript tries to unregister the viewDef a reference to data on the card is encountered and the above error message will be shown. This bug will be fixed in a future ROM.

To work around this bug for any 2.0 based ROM, add the following code to your part's InstallScript before calling NewtInstallScript:

    local mainLayout := partFrame.theForm;
    if mainLayout.allViewDefs then
        foreach dataDefSym,viewDefsFrame in mainLayout.allViewDefs do
            foreach viewDef in viewDefsFrame do
                RegisterViewDef ( 
                    viewDef, EnsureInternal (dataDefSym) );
    partFrame.removeFrame := 
        mainLayout:NewtInstallScript(mainLayout);

Note that it is OK to call RegisterViewDef more than once with the same view definition. RegisterViewDef will do nothing (and return NIL) if the template is already registered.