### Cells and Table View Performance
ref: [[https://developer.apple.com/library/archive/documentation/UserExperience/Conceptual/TableView_iPhone/TableViewCells/TableViewCells.html#//apple_ref/doc/uid/TP40007451-CH7-SW18|Apple Dev Document]]

The proper use of table view cells, whether off-the-shelf or custom cell objects, is a major factor in the performance of table views. Ensure that your application does the following three things:

- Reuse cells. Object allocation has a performance cost, especially if the allocation has to happen repeatedly over a short period—say, when the user scrolls a table view. If you reuse cells instead of allocating new ones, you greatly enhance table view performance.
- Avoid relayout of content. When reusing cells with custom subviews, refrain from laying out those subviews each time the table view requests a cell. Lay out the subviews once, when the cell is created.
- Use opaque subviews. When customizing table view cells, make the subviews of the cell opaque, not transparent.