Importance of drawRect, layoutSubViews, and setNeedsDisplay

Question

What is the importance of the drawRect, layoutSubViews and setNeedsDisplay methods. In what contexts should we use them?

Answer 1

As the documentation says,

drawRect: Draws the receiver’s image within the passed-in rectangle. 

Parameters

rect: a rectangle defining the area to limit drawing.

This method is used to draw your UIView inside a specific view rectangle.

• (voids) setNeedsDisplay

drawRect: . , . , setNeedsDisplay . UIView, , .

, , , UIView . , : , ; - .

.

• () layoutSubviews

subviews, layoutIfNeeded . .

. , , ,