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tutorial:transfer-api_storage

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tutorial:transfer-api_storage [2021/10/30 09:43] – [What you can do with a Storage<FluidVariant>] technici4ntutorial:transfer-api_storage [2021/10/30 10:25] (current) – external edit 127.0.0.1
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-===== Fabric Transfer API: Understanding Storage<T> =====+===== Fabric Transfer API: Understanding Storage<FluidVariant> =====
 //This article is part of a series on the Fabric Transfer API. [[tutorial:transfer-api|Link to the home page of the series]].// //This article is part of a series on the Fabric Transfer API. [[tutorial:transfer-api|Link to the home page of the series]].//
  
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 </code> </code>
  
-==== What you can do with a Storage<FluidVariant> ====+==== A look at Storage<T> ====
 Let's have a look at ''Storage.java'': Let's have a look at ''Storage.java'':
 <code java> <code java>
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 This interface allows us to insert into a storage, extract from it, and read its contents. This interface allows us to insert into a storage, extract from it, and read its contents.
  
-Let's look at an example: how to insert exactly one bucket of water into a storage.+==== First example: how to insert exactly one bucket of water into a storage ====
 <code java> <code java>
 Storage<FluidVariant> storage = ...; Storage<FluidVariant> storage = ...;
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  if (amountInserted == FluidConstants.BUCKET) {  if (amountInserted == FluidConstants.BUCKET) {
  // "Commit" the transaction: this validates all the operations that were part of this transaction.  // "Commit" the transaction: this validates all the operations that were part of this transaction.
 + // You should call this if you are satisfied with the result of the operation, and want to keep it.
  transaction.commit();  transaction.commit();
  } else {  } else {
  // Doing nothing "aborts" the transaction: this cancels the insertion.  // Doing nothing "aborts" the transaction: this cancels the insertion.
 + // You should call this if you are not satisfied with the result of the operation, and want to abort it.
  }  }
 } }
 </code> </code>
 +
 +==== Second example: move exactly one bucket of lava from a storage to another storage ====
 +<code java>
 +import static net.fabricmc.fabric.api.transfer.v1.fluid.FluidConstants.BUCKET; // a bit shorter to type :)
 +
 +Storage<FluidVariant> source, destination;
 +FluidVariant lava = FluidVariant.of(Fluids.LAVA);
 +
 +try (Transaction transaction = Transaction.openOuter()) {
 + if (source.extract(lava, BUCKET, transaction) == BUCKET && destination.insert(lava, BUCKET, transaction) == BUCKET) {
 + transaction.commit();
 + }
 +}
 +</code>
 +Hopefully you understand why this works, and why this will never duplicate or void fluid.
 +
 +==== A more complicated example: Extracting the contents of a storage ====
 +In the previous example, we knew that we wanted to move water or lava. But what if we don't know what to extract? The answer is: iterate over the contents!
 +This example also introduces the concept of nested transactions.
 +<code java>
 +Storage<FluidVariant> storage;
 +Predicate<FluidVariant> filter = fv -> fv.isOf(Fluids.WATER); // What we want to extract, in this example let's say we want to extract any water, regardless of its NBT tag.
 +long totalExtracted = 0;
 +
 +// Open a transaction, as before.
 +try (Transaction transaction = Transaction.openOuter()) {
 + // Loop over the contents! Each StorageView<T> can contain at most one resource. You can think of a StorageView as an inventory slot.
 + for (StorageView<FluidVariant> view : storage.iterable(transaction)) {
 + if (view.isResourceBlank()) continue; // This means that the view contains no resource, represented by FluidVariant.blank().
 + FluidVariant storedResource = view.getResource(); // Current resource
 + if (!filter.test(storedResource)) continue; // The filter rejected this resource, skip it.
 +
 + // If you want to extract any amount <= view.getAmount(), do this.
 + totalExtracted += view.extract(storedResource, view.getAmount(), transaction);
 +
 + // If you want to extract either the exact amount or nothing, you can use a nested transaction!
 + try (Transaction nestedTransaction = transaction.openNested()) {
 + long amount = view.getAmount(); // The amount will change after the call to extract, so make sure to save it first.
 + long extracted = view.extract(storedResource, amount, nestedTransaction);
 + if (extracted == amount) {
 + totalExtracted += amount;
 + nestedTransaction.commit(); // Validate the nestedTransaction: the outer one will have to committed as well to validate this change.
 + } else {
 + // If we do nothing, the extraction is cancelled immediately when nestedTransaction is closed at the end of the try { ... } block.
 + }
 + }
 + }
 + transaction.commit(); // Don't forget to commit, or all of the extraction will be cancelled!
 +}
 +</code>
 +
 +==== Conclusion ====
 +You should now be able to use ''Storage''s and ''StorageView''s. They can be a bit challenging in the beginning, but once you're used to them they are very easy to work with.
 +
 +You should also have a look at ''StorageUtil'': it already contains functions that perform common transfer operations. In particular, [[https://maven.fabricmc.net/docs/fabric-api-0.41.0+1.17/net/fabricmc/fabric/api/transfer/v1/storage/StorageUtil.html#move(net.fabricmc.fabric.api.transfer.v1.storage.Storage,net.fabricmc.fabric.api.transfer.v1.storage.Storage,java.util.function.Predicate,long,net.fabricmc.fabric.api.transfer.v1.transaction.TransactionContext)|move]] is very useful if you just want to move resources between two storages.
 +
tutorial/transfer-api_storage.1635587039.txt.gz · Last modified: 2021/10/30 09:43 by technici4n