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generic.dart
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generic.dart
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/*
* Copyright (c) 2020, Birju Vachhani
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* 3. Neither the name of the copyright holder nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
// Author: Birju Vachhani
// Created Date: August 27, 2020
part of '../screwdriver.dart';
/// provides scope functions as extensions on [T]
extension GenericScrewdriver<T extends Object> on T {
/// Calls the specified function [block] with `this` value as its argument
/// and returns `this` value.
T apply(void Function(T obj) block) {
block(this);
return this;
}
/// Calls the specified function [block] with `this` value as its argument
/// and returns `this` value.
R run<R>(R Function(T obj) block) {
return block(this);
}
/// Returns [this] if it satisfies the given [predicate] or null,
/// if it doesn't.
T? takeIf(bool Function(T obj) predicate) {
if (predicate(this)) {
return this;
}
return null;
}
/// Returns [this] if it doesn't satisfy the given [predicate] or null,
/// if it doesn't.
T? takeUnless(bool Function(T obj) predicate) {
if (!predicate(this)) {
return this;
}
return null;
}
/// A safe cast operation that returns null if the cast is not possible.
/// Otherwise, returns the casted value.
R? tryCast<R>() {
try {
return this as R?;
} catch (e) {
return null;
}
}
}
/// Always throws [UnimplementedError] stating that operation is
/// not implemented.
// ignore: non_constant_identifier_names
void TODO([String? reason]) =>
throw UnimplementedError(reason ?? 'An operation is not implemented.');
/// Executes a provided action and handles potential errors.
///
/// The function returns T? which represents the result of the executed action
/// if the action is not asynchronous. If the action completes successfully,
/// the result is returned as is. If an exception occurs during the execution,
/// the [onError] function is called with the error and stack trace. If the
/// [onError] function is not provided or returns null, the error is swallowed
/// and the result is set to null.
///
/// The function returns a [Future] of type T? which represents the result of
/// the executed action if the action is asynchronous. If the action completes
/// successfully, the result is returned as is. If an exception occurs during
/// the execution, the [onError] function is called with the error and stack
/// trace. If the [onError] function is not provided or returns null, the error
/// is swallowed and the result is set to null.
///
/// If the [onError] function is synchronous, the result is returned as is. If
/// it throws an error, the error is swallowed and the result is set to null.
///
/// If the [onError] function is asynchronous, a [Future] of type T? is
/// returned. If the [onError] function completes successfully, the result is
/// returned as is. If it throws an error, the error is swallowed and the
/// result is set to null.
FutureOr<T?> runCaching<T>(
FutureOr<T?> Function() action, {
FutureOr<T?> Function(dynamic error, StackTrace stacktrace)? onError,
}) {
FutureOr<T?> result;
try {
result = action.call();
} catch (error, stacktrace) {
try {
// call onError if exception occurs.
result = onError?.call(error, stacktrace);
} catch (error) {
// Swallow error if onError throws an error.
result = null;
}
}
if (result is Future) {
return (result as Future<T?>)
// return the value if future completes successfully.
.then((value) => value)
// call onError if future completes with error.
.catchError(
(error, StackTrace stacktrace) => onError?.call(error, stacktrace))
// swallow error and return null if onError throws an error.
.catchError((error) => null);
}
return result;
}