App vs App

App Battles ! Winner takes all. Last man standing and all that !

No – nothing quite so fun (although it can be a lot of fun)

This has to do with the App class at design time vs the App METHOD (yes it’s a method) at runtime.

The app class at design time can be renamed however you want. You could call it “MyApp”. And for most things that would have no impact. But, you’ll note I don’t say for ALL things.

If you start a new Desktop Application and rename the App class to MyApp I can demonstrate where there are differences.

In the new app’s Window1. Open event lets just do something simple like

dim s as string = App.<press tab>

What you should notice is that none of the defined constants autocomplete. The methods and properties of any Application will show. But no defined constants.

This makes sense because the constants do not exist on Application but they do exist on MyApp.

If we add a few properties to MyApp they also won’t autocomplete. Again the App METHOD, at runtime, returns an Application (or Console Application, Service Application, WebApplication or iosApplication depending on the project type)

Again none of the instances that the App method returns define any of the properties we added to our custom Application instance. And so they will not autocomplete.

What’s an App to do ?

We can definitely deal with this.

One way is to not rename the App class in your project – although this wont alleviate all issues. It will just ignore some for a while. And that is, for many uses, OK.

Or we could cast the return value of the App method to be our defined class type with code like

dim s as string = MyApp(App).<press tab>

This is ALMOST always safe – except in the handful of spots that App can actually be NIL – yay !

It may be better to write something like

dim s as string
if App isa MyApp then
  s = MyApp(App).<press tab>
end if

so a nil return from App won’t matter

Either way the confusion comes from the App METHOD and the App class in your project having the same name. This can make it very unclear whats wrong. And then, when you REALLY need to know why this is, if you’ve ignored this until now you wont know why this weirdness exists.

Unless of course you read this post 😛