How do I handle the contents of a registry?

[haykam821]

How do I run code for every element of a registry, such as the item or block registry?

[Daomephsta]

A simple approach is

// Iterate over existing entries and perform action                            
for (Entry<RegistryKey<Item>, Item> entry : Registry.ITEM.getEntries())        
{                                                                              
    // Example: print identifier and instance                                  
    System.out.println(entry.getKey().getValue() + " = " + entry.getValue());  
}                                                                              
// Register a callback to perform the action on future entries                 
RegistryEntryAddedCallback.event(Registry.ITEM).register((rawId, id, object) ->
{                                                                              
    // Example: print identifier and instance                                  
    System.out.println(id + " = " + object);                                   
});                                                                            

It can be generalised with this method

public static <T> void forRegistryEntries(Registry<T> registry, BiConsumer<Identifier, T> action)         
{                                                                                                         
    for (Entry<RegistryKey<T>, T> entry : registry.getEntries())                                          
        action.accept(entry.getKey().getValue(), entry.getValue());                                       
    RegistryEntryAddedCallback.event(registry).register((rawId, id, object) -> action.accept(id, object));
}                                                                                                         

which is called like so

forRegistryEntries(Registry.ITEM, (id, item) -> System.out.println(id + " = " + item));

It's possible to iterate over only the registry values, which would be simpler. Since the identifier is very useful (e.g. logging, debugging), I opted to show iteration over registry entries instead.