3 ms·

Curious why typecast if instanceof is checked already ? Wont the compiler know of this already ? if (view instanceof ChatMessageCell) { .......

• Crespyl 9y ago
  It's essentially just how Java works, and isn't that uncommon in statically typed procedural languages. The `view` variable is still a reference of the parent type (Say `MessageCell` for now, can't be bothered to find that part in the code), and `MessageCell` references can only do certain things. It's possible to check what the type of the underlying object is with `instanceof`, but that doesn't change the type of the reference. If you want to do things that only a `ChatMessageCell` can do, you need to make a new reference of that type.
• hoppelhase 9y ago
  It's Java, so no.
• on_and_off 9y ago
  the java compiler does not do that unfortunately, Kotlin would do what they call a 'smartcast' : ie if you did an instanceof if the if, in the corresponding {}closure you know the type of this object. The whole code is probably unmaintanable for anybody other than it's original writer (and even for him, there must be a limit to how much code you can fit in your head). I would love to work for Telegram, it is one of the products I use daily .. but if I had to handle this codebase, it would be a rare case of 'total rewrite or I am out'. Incidentally, it looks like they are going to do this full rewrite. Telegram seems to have acqui-hired the creators of Telegram X and are prepping it up as a replacement.
• saagarjha 9y ago
  I believe this is called “type narrowing”, and no, Java doesn’t have this.