com.softwaremill.jox.SelectClause Maven / Gradle / Ivy
package com.softwaremill.jox;
import java.util.function.Supplier;
/**
* A clause to use as part of {@link Select#select(SelectClause[])}. Clauses can be created having a channel instance,
* using {@link Channel#receiveClause()} and {@link Channel#sendClause(Object)}}.
*
* A clause instance is immutable and can be reused in multiple `select` calls.
*/
public abstract class SelectClause {
abstract Channel getChannel();
/**
* @return Either a {@link StoredSelectClause}, {@link ChannelClosed} when the channel is already closed, or the selected
* value (not {@code null}).
*/
abstract Object register(SelectInstance select);
/**
* Transforms the raw value with the transformation function provided when creating the clause.
*
* Might throw any exceptions that the provided transformation function throws.
*/
abstract T transformedRawValue(Object rawValue);
}
class DefaultClause extends SelectClause {
private final Supplier callback;
public DefaultClause(Supplier callback) {
this.callback = callback;
}
@Override
Channel getChannel() {
return null;
}
@Override
Object register(SelectInstance select) {
return DefaultClauseMarker.DEFAULT;
}
@Override
T transformedRawValue(Object rawValue) {
return callback.get();
}
}
/**
* Used as a result of {@link DefaultClause#register(SelectInstance)}, instead of {@code null}, to indicate that the
* default clause has been selected during registration.
*/
enum DefaultClauseMarker {
DEFAULT
}