Adding different icons to each cells in table view?

A cell that a table view uses for displaying a row is a view (UITableViewCell inherits from UIView). As a view, a cell has a content view—a superview for cell content—that it exposes as a property. To customize the appearance of rows in a table view, add subviews to the cell’s content view, which is accessible through its contentView property, and lay them out in the desired locations in their superview’s coordinates.

You can configure and lay them out programmatically or in Interface Builder. One advantage of this approach is its relative simplicity; it doesn’t require you to create a custom subclass of UITableViewCell and handle all of the implementation details required for custom views. However, if you do take this approach, avoid making the views transparent, if you can.

Transparent subviews affect scrolling performance because of the increased compositing cost. Subviews should be opaque, and typically should have the same background color as the cell. And if the cell is selectable, make sure that the cell content is highlighted appropriately when selected.

The content is selected automatically if the subview implements (if appropriate) the accessor methods for the highlighted property. Suppose you want a cell with text and image content in custom locations. For example, you want the image on the right side of the cell and the title and subtitle of the cell right-aligned against the left side of the image.

Figure 5-9 show how a table view with rows drawn with such a cell might look. The code example in Listing 5-7 illustrates how the data source programmatically composes the cell with which this table view draws its rows. In tableView:cellForRowAtIndexPath:, it first checks to see the table view already has a cell object with the given reuse identifier.

If there is no such object, the data source creates two label objects and one image view with specific frames within the coordinate system of their superview (the content view). It also sets attributes of these objects. Having acquired an appropriate cell to use, the data source sets the cell’s content before returning the cell.

When the data source creates the cells, it assigns each subview an identifier called a tag. With tags, you can locate a view in its view hierarchy by calling the viewWithTag: method. If the delegate later gets the designated cell from the table view’s queue, it uses the tags to obtain references to the three subviews prior to assigning them content.

This code creates a UITableViewCell object in the predefined default style (UITableViewCellStyleDefault). Because the content properties of the standard cells—textLabel, detailTextLabel, and imageView—are nil until assigned content, you may use any predefined cell as the template for customization. One way to achieve “attributed string” effects with textual content is to lay out UILabel subviews of the UITableViewCell content view.

The text of each label can have its own font, color, size, alignment, and other characteristics. If you want that kind of variation within a label object, create multiple labels and lay them out relative to each other.