Checking for the presence of a class

Question

I would like to check if a particular class has been loaded.

Smalltalk at: #TabularXSLXExport  ifNone: [ ]

This does not lead to a result in Pharo. How do I do this?

Answer 1

I think the method you're looking for is #at:ifAbsent: (not #at:ifNone:).

So, inspecting the result of

Smalltalk at: #String ifAbsent: [ nil ]

will let you inspect the String class, while

Smalltalk at: #Strign ifAbsent: [ nil ]

will open an inspector on nil (note that "Strign" is a deliberate misspelling of "String" so that the lookup fails).

Edit: As Max Leske points out in the comments, #hasClassNamed: is a more suitable method if you're just trying to determine whether the class exists, and not interested in the class itself being returned.

Answer 2

You might want to do an extension method for this, or use a pragma to collect all 'exports', or register this functionality. The world menu uses a pragma <worldMenu>.Catalog browser uses it like this:

CatalogBrowser class>>menuCommandOn: aBuilder 
"Add a custom menu item to the world menu"  
<worldMenu> 

(aBuilder item: #'Catalog Browser')
        order: 0.19; 
      icon: Smalltalk ui icons catalogIcon;  
        parent: #'Tools';
        action: [ self open ].

Take a look at PragmaMenuBuilder for how that works

In Pharo4 that is the MetacelloConfigurationBrowser:

MetacelloConfigurationBrowser class>>menuCommandOn: aBuilder  
<worldMenu>

(aBuilder item: 'Configuration Browser')
    parent: #Tools;
    order: 0.20;
    action: [self new openWithSpec]; 
    icon: Smalltalk ui icons configIcon