Hands-On Software Engineering with Golang

Looking up links

Looking up links is a fairly trivial operation. All we need to do is acquire a read lock, look up the link by its ID, and do either of the following things:

• Return the link back to the caller
• Return an error if no link with the provided ID was found

The link lookup logic is outlined in the following code snippet:

func (s *InMemoryGraph) FindLink(id uuid.UUID) (*graph.Link, error) {
    s.mu.RLock()
    defer s.mu.RUnlock()

    link := s.links[id]
    if link == nil {
        return nil, xerrors.Errorf("find link: %w", graph.ErrNotFound)
    }

    lCopy := new(graph.Link)
    *lCopy = *link
    return lCopy, nil
}

Since we want to ensure that no external code can modify the graph's contents without invoking the UpsertLink method, the FindLink implementation ...