Debug visualisers are a type of IDE plugin that allows you to change the display of a variable in the various debug windows (Local Variables, Watches, Inspector, and Evaluate/Modify.) For example, the TDateTime visualiser takes the double value that represents time and instead displays that time converted to a string. You register a debug visualiser for a type, so all variables of that type, and optionally descendants of that type, go through your visualiser.
In previous versions, this type was specified by a plain string, such as ‘TComponent’, and there was no way to handle a generic type. If you registered ‘MyGeneric’, the visualiser would never be called, because the concrete instantiations of that type do not use T – they might be ‘MyGeneric’, ‘MyGeneric’, and so forth.
In 10.2.1, we have introduced support for registering a visualiser for a generic type. Your visualizer can implement IOTADebuggerVisualizer250 as well as the prior IOTADebuggerVisualizer, where the GetSupportedType method allows you to specify that the type string is a generic:
.
IOTADebuggerVisualizer250 = interface(IOTADebuggerVisualizer)
['{DC0C8D82-B783-4205-B3F4-D325BA8B3EEB}']
{ Return the Index'd Type. TypeName is the type. AllDescendants indicates
whether or not types descending from this type should use this visualizer
as well. IsGeneric indicates whether this type is a generic type. }
procedure GetSupportedType(Index: Integer; var TypeName: string;
var AllDescendants: Boolean; var IsGeneric: Boolean); overload;
end;
This means you can register for MyGeneric and your visualiser will be called for all MyGenerics. This is all generic types, ie interfaces as well as classes.
One note is that we do not yet support registering for descendants of a generic type, meaning that if you have MyDesc = class(MyGeneric) or MyDesc = class(MyGeneric), you need to register a visualiser for MyDesc separately. This is because of some complexities in the internal evaluator.
Generics are widely used, especially for collections like dictionaries and lists, and in third-party libraries like Spring4D. We hope you will find visualiser support for generics useful!
Update: here is a code snippet demonstrating a template visualizer.