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/*
* Copyright 2000-2014 Vaadin Ltd.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.vaadin.data;
import java.util.Objects;
import java.util.Optional;
import java.util.function.Consumer;
import java.util.function.Function;
/**
* An internal implementation of {@code Result}.
*
* @param <R>
* the result value type
*/
class SimpleResult<R> implements Result<R> {
private final R value;
private final String message;
/**
* Creates a new {@link Result} instance using {@code value} for a non error
* {@link Result} and {@code message} for an error {@link Result}.
* <p>
* If {@code message} is null then {@code value} is ignored and result is an
* error.
*
* @param value
* the value of the result, may be {@code null}
* @param message
* the error message of the result, may be {@code null}
*/
SimpleResult(R value, String message) {
// value != null => message == null
assert value == null
|| message == null : "Message must be null if value is provided";
this.value = value;
this.message = message;
}
@Override
@SuppressWarnings("unchecked")
public <S> Result<S> flatMap(Function<R, Result<S>> mapper) {
Objects.requireNonNull(mapper, "mapper cannot be null");
if (isError()) {
// Safe cast; valueless
return (Result<S>) this;
} else {
return mapper.apply(value);
}
}
@Override
public void handle(Consumer<R> ifOk, Consumer<String> ifError) {
Objects.requireNonNull(ifOk, "ifOk cannot be null");
Objects.requireNonNull(ifError, "ifError cannot be null");
if (isError()) {
ifError.accept(message);
} else {
ifOk.accept(value);
}
}
@Override
public Optional<String> getMessage() {
return Optional.ofNullable(message);
}
@Override
public Optional<R> getValue() {
return Optional.ofNullable(value);
}
@Override
public boolean isError() {
return message != null;
}
@Override
public String toString() {
if (isError()) {
return "error(" + message + ")";
} else {
return "ok(" + value + ")";
}
}
}
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