static auto reusePreviousComponentForSingleChild()

in ComponentKit/Core/Render/CKRenderHelpers.mm [101:144]
28 lines of code
9 McCabe index (conditional complexity)

  static auto reusePreviousComponentForSingleChild(CKTreeNode *node,
                                                   id<CKRenderWithChildComponentProtocol> component,
                                                   __strong id<CKComponentProtocol> *childComponent,
                                                   CKTreeNode *parent,
                                                   CKTreeNode *previousParent,
                                                   const CKBuildComponentTreeParams &params,
                                                   BOOL parentHasStateUpdate,
                                                   CKRenderDidReuseComponentBlock didReuseBlock) -> BOOL {

    // If there is no previous parent or no childComponent, we bail early.
    if (previousParent == nil || childComponent == nullptr) {
      return NO;
    }

    // Disable any sort of reuse when environmental changes
    if (params.buildTrigger & CKBuildTriggerEnvironmentUpdate) {
      return NO;
    }

    if (params.buildTrigger & CKBuildTriggerStateUpdate) {
      // State update branch - only state updates or coalesced state & props update.
      // Check if the tree node is not dirty (not in a branch of a state update).
      auto const dirtyNodeId = params.treeNodeDirtyIds.find(node.nodeIdentifier);
      if (dirtyNodeId == params.treeNodeDirtyIds.end()) {
        // We reuse the component without checking `shouldComponentUpdate:` in the following conditions:
        // 1. The component is not dirty (on a state update branch)
        // 2. No direct parent has a state update
        // 3. Not a coalesced state & props update.
        if (!parentHasStateUpdate &&
            (params.buildTrigger & CKBuildTriggerPropsUpdate) == 0) {
          // Faster state update optimizations.
          return CKRenderInternal::reusePreviousComponent(component, childComponent, node, parent, previousParent, params, didReuseBlock);
        }
        // We fallback to the props update optimization in the follwing case:
        // - The component is not dirty, but the parent has a state update or tree props were updated.
        return (CKRenderInternal::reusePreviousComponentIfComponentsAreEqual(component, childComponent, node, parent, previousParent, params, didReuseBlock));
      }
    } else if (params.buildTrigger & CKBuildTriggerPropsUpdate) {
      // Will be used for coalesced props & state updates too.
      return CKRenderInternal::reusePreviousComponentIfComponentsAreEqual(component, childComponent, node, parent, previousParent, params, didReuseBlock);
    }

    return NO;
  }