Inno Setup: how to use {app} in InitializeWizard Procedure

How ca开发者_开发百科n I gain access to the {app} variable in the InitializeWizard procedure ?

When I use ExpandConstant('{app}'); I get the next error message:

An attempt to expand the {app} constant was made before it was initialized

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Found the answer :)

Prototype:

function WizardDirValue: String;

Description:

Returns the current contents of the edit control on the Select Destination Location page of the wizard.

Unlike ExpandConstant('{app}'), this function will not fail if called after the wizard is shown but prior to the user selecting a directory. Rather, it will return the default directory name.