Valentin Shergin 67a79010ca Fabric: Simplified way to specialize ComponentName in ConcreteShadowNode class template
Summary:
@public
Previously, all ConcreteShadowNode subclasses had to override `getComponentName()` function to specialize a name of the component. And often it was all that those subclasses do. Now, it's a template argument; and many ShadowNode classes can be created as oneliners via *just* specializing  ConcreteShadowNode template.

Unfortunately, C++ does not allow to use `std::string`s or string literals as template arguments, but it allows to use pointers. Moreover, those pointers must point to some linked data, hence, those values must be declared in .cpp (not .h) files. For simplicity, we put those constants in Props classes, (but this is not a strong requirement).

Reviewed By: mdvacca

Differential Revision: D8942826

fbshipit-source-id: 4fd517e2485eb8f8c20a51df9b3496941856d8a5
2018-08-04 09:47:30 -07:00

115 lines
3.3 KiB
C++

/**
* Copyright (c) 2015-present, Facebook, Inc.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*/
#pragma once
#include <fabric/core/Props.h>
#include <fabric/core/ShadowNode.h>
namespace facebook {
namespace react {
/*
* Base templace class for all `ShadowNode`s which connects exact `ShadowNode`
* type with exact `Props` type.
* `ConcreteShadowNode` is a default implementation of `ShadowNode` interface
* with many handy features.
*/
template <
const char *concreteComponentName,
typename PropsT,
typename EventEmitterT = EventEmitter
>
class ConcreteShadowNode: public ShadowNode {
static_assert(std::is_base_of<Props, PropsT>::value, "PropsT must be a descendant of Props");
public:
using ConcreteProps = PropsT;
using SharedConcreteProps = std::shared_ptr<const PropsT>;
using ConcreteEventEmitter = EventEmitterT;
using SharedConcreteEventEmitter = std::shared_ptr<const EventEmitterT>;
using SharedConcreteShadowNode = std::shared_ptr<const ConcreteShadowNode>;
static ComponentName Name() {
return ComponentName(concreteComponentName);
}
static ComponentHandle Handle() {
return ComponentHandle(concreteComponentName);
}
static SharedConcreteProps Props(const RawProps &rawProps, const SharedProps &baseProps = nullptr) {
return std::make_shared<const PropsT>(baseProps ? *std::static_pointer_cast<const PropsT>(baseProps) : PropsT(), rawProps);
}
static SharedConcreteProps defaultSharedProps() {
static const SharedConcreteProps defaultSharedProps = std::make_shared<const PropsT>();
return defaultSharedProps;
}
ConcreteShadowNode(
const Tag &tag,
const Tag &rootTag,
const SharedConcreteProps &props,
const SharedConcreteEventEmitter &eventEmitter,
const SharedShadowNodeSharedList &children,
const ShadowNodeCloneFunction &cloneFunction
):
ShadowNode(
tag,
rootTag,
(SharedProps)props,
eventEmitter,
children,
cloneFunction
) {};
ConcreteShadowNode(
const SharedConcreteShadowNode &shadowNode,
const SharedProps &props,
const SharedEventEmitter &eventEmitter,
const SharedShadowNodeSharedList &children
):
ShadowNode(
shadowNode,
(SharedProps)props,
eventEmitter,
children
) {}
ComponentName getComponentName() const override {
return ComponentName(concreteComponentName);
}
ComponentHandle getComponentHandle() const override {
return reinterpret_cast<ComponentHandle>(concreteComponentName);
}
const SharedConcreteProps getProps() const {
assert(std::dynamic_pointer_cast<const PropsT>(props_));
return std::static_pointer_cast<const PropsT>(props_);
}
/*
* Returns subset of children that are inherited from `SpecificShadowNodeT`.
*/
template<typename SpecificShadowNodeT>
std::vector<SpecificShadowNodeT *> getChildrenSlice() const {
std::vector<SpecificShadowNodeT *> children;
for (const auto &childShadowNode : *getChildren()) {
auto specificChildShadowNode = dynamic_cast<const SpecificShadowNodeT *>(childShadowNode.get());
if (specificChildShadowNode) {
children.push_back(const_cast<SpecificShadowNodeT *>(specificChildShadowNode));
}
}
return children;
}
};
} // namespace react
} // namespace facebook