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Fabric: New approach of mutating ShadowNode's children collection 

Summary: Previously we recreate a vector with pointers to child nodes every single time we modify the collection. That was okay but recently I realized that the we can  simply make a copy of the vector one time during object construction and then mutate it freely.

Reviewed By: mdvacca

Differential Revision: D7467796

fbshipit-source-id: 660f1706a19ae5f07c34c509f411ce9d67b93b35
This commit is contained in:
Valentin Shergin 2018-04-10 12:45:51 -07:00 committed by Facebook Github Bot
parent 1a4b6f0b3d
commit 5dca3e7c74
1 changed files with 6 additions and 14 deletions
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20
ReactCommon/fabric/core/shadownode/ShadowNode.cpp
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@ -31,7 +31,7 @@ ShadowNode::ShadowNode(
rootTag_(rootTag),
instanceHandle_(instanceHandle),
props_(props),
children_(children),
children_(std::make_shared<SharedShadowNodeList>(*children)),
revision_(1) {}
ShadowNode::ShadowNode(
@ -43,7 +43,7 @@ ShadowNode::ShadowNode(
rootTag_(shadowNode->rootTag_),
instanceHandle_(shadowNode->instanceHandle_),
props_(props ? props : shadowNode->props_),
children_(children ? children : shadowNode->children_),
children_(std::make_shared<SharedShadowNodeList>(*(children ? children : shadowNode->children_))),
sourceNode_(shadowNode),
revision_(shadowNode->revision_ + 1) {}
@ -92,23 +92,15 @@ void ShadowNode::sealRecursive() const {
void ShadowNode::appendChild(const SharedShadowNode &child) {
ensureUnsealed();
// We cannot mutate `children_` in place here because it is a *shared*
// data structure which means other `ShadowNodes` might refer to its old value.
// So, we have to clone this and only then mutate.
auto nonConstChildrenCopy = SharedShadowNodeList(*children_);
nonConstChildrenCopy.push_back(child);
children_ = std::make_shared<const SharedShadowNodeList>(nonConstChildrenCopy);
auto nonConstChildren = std::const_pointer_cast<SharedShadowNodeList>(children_);
nonConstChildren->push_back(child);
}
void ShadowNode::replaceChild(const SharedShadowNode &oldChild, const SharedShadowNode &newChild) {
ensureUnsealed();
// We cannot mutate `children_` in place here because it is a *shared*
// data structure which means other `ShadowNodes` might refer to its old value.
// So, we have to clone this and only then mutate.
auto nonConstChildrenCopy = SharedShadowNodeList(*children_);
std::replace(nonConstChildrenCopy.begin(), nonConstChildrenCopy.end(), oldChild, newChild);
children_ = std::make_shared<const SharedShadowNodeList>(nonConstChildrenCopy);
auto nonConstChildren = std::const_pointer_cast<SharedShadowNodeList>(children_);
std::replace(nonConstChildren->begin(), nonConstChildren->end(), oldChild, newChild);
}
void ShadowNode::clearSourceNode() {