When working on the app using React and Apollo Client, I encountered an issue: despite successful data fetching from the server, the app failed to display the updated information. I'll discuss how Apollo Client and GraphQL work another time. Today, I'll talk about the importance of React's "key" prop for re-rendering.
The Key Prop:
The key in a map is something we need to write because React will complain. (Just kidding.) In React, the key prop is for optimizing rendering. Each item in the list is associated with a specific component instance, and React needs a way to distinguish between these instances when they are sorted, added, or deleted.
Here's a citation from the documentation:
Keys tell React which array item each component corresponds to, so that it can match them up later. This becomes important if your array items can move (e.g. due to sorting), get inserted, or get deleted. A well-chosen key helps React infer what exactly has happened, and make the correct updates to the DOM tree.
I had missed this last part, the crucial part:
make the correct updates to the DOM tree
Parent and Child Component Rendering:
When there's some change in a parent component, its child components rerender. This ensures that the UI displays the latest state of the application. However, I didn't know that the direct changes in a parent component may not automatically trigger rerendering of its child components. (Rendering is too complicated for me to explain here, so I'll keep learning about this.)
Explanation of Using Key for Forceful Rerender:
As I mentioned earlier, in my React and Apollo Client application, I encountered an issue where the UI was not updating with the latest data fetched from the database.
To address this, I needed to force a rerender of the parent component. Here, the key prop comes in. When React detected the change in the key prop value, it recognized that the parent component had changed and triggered a re-render.
I recently delved into the usage of useReducer and useContext in React, exploring effective state management strategies. However, I realized there are so much more other factors to consider, including rendering optimizations and project structure.
I overlooked the fundamental concept: key prop. It was one of the first things I learned when working with the map function in React, but I failed to recognize its crucial role. This realization serves as a reminder of the depth of knowledge yet to be explored in the realm of React development.
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