[Any Version] Nested classes: where and when

[ktreus]

Greetings. My nick is ktreus and i want to know where we can use nested classes and the situations we can apply them in modding, because im using to make everything in my mod and all seems suprisely working well, but my mod is a big project (almost a divine rpg) and idk if this will imply in future.

[Choonster]

When you use nested classes depends on your code style. There's not really a specific area where you need to use them, they mostly behave just like normal classes.

 

One common use is nesting the IMessageHandler in the corresponding IMessage class to keep the message and its handler together.

[Draco18s]

3 minutes ago, Choonster said:

One common use is nesting the IMessageHandler in the corresponding IMessage class to keep the message and its handler together.

While true, I recommend against it due to the potential to confuse the scope ("my packet handler runs, but it doesn't recieve the data, but I know I'm sending it!") as the modder tried to reference the packet data not from the object passed, but through container scope, even through the objects were different instances.   Keeping them in separate files helps the fledgling modder. 

 

I use nested classes for things like data wrappers, where I need to bundle two items together for a sorting function, or similar, but that that wrapper is never used outside that scope. 

[Choonster]

8 minutes ago, Draco18s said:

While true, I recommend against it due to the potential to confuse the scope ("my packet handler runs, but it doesn't recieve the data, but I know I'm sending it!") as the modder tried to reference the packet data not from the object passed, but through container scope, even through the objects were different instances.   Keeping them in separate files helps the fledgling modder. 

 

If the handler is a static nested class (which it should be), attempting to access instance fields of the message results in a compilation error.

[Draco18s]

13 minutes ago, Choonster said:

 

If the handler is a static nested class (which it should be), attempting to access instance fields of the message results in a compilation error.

Oh I agree. Just that some new folks don't know that and seem to think that because the code is in the same file it's fair game to dip things that won't work. Like making the message and message handler the same class...

[Choonster]

29 minutes ago, diesieben07 said:

There is no "static nested class". Nested classes are static. Non-static "nested" classes are called inner classes.

 

Java's tutorials do use the term "static nested classes".

Edited June 14, 2017 by Choonster

[jeffryfisher]

I nest my common proxy class inside my abstract main mod class. Not only can my abstract mod declare a proxy for every mod, but the proxy class has visibility to fields and methods in the abstract mod (and client proxies can call inherited methods that exploit that visibility). Since a proxy acts on behalf of a mod, it seemed to make sense to me to grant that visibility.

 

Similarly, when I define a tile entity class, I usually nest it inside the block class that it supports.

 

In vanilla Minecraft, I see loads of enum classes defined within other classes that use them to define variants.

 

However, don't take Minecraft and modder's hacks as a guide to good programming discipline. If you're curious about learning general Java and programming, then look to a more general Java forum. Hackers like me might show you bad habits that you'll need to unlearn someday.

[Draco18s]

3 hours ago, jeffryfisher said:

In vanilla Minecraft, I see loads of enum classes defined within other classes that use them to define variants.

This makes sense...in vanilla.

If you're making a mod and want to expose your block properties, then the enum should be exposed (but not necessarily the block) in an API.