macOS How to repaint 'drawRect' in custom view?

In my opinion, the 'drawRect' function seems like the 'paint' function in java.
So, is there some some function like 'repaint' which refresh the screen?

For example,
-(void) drawRect: (NSRect) rect{
NSString * str = [otherObject stringToDisplay];
[str drawAtPoint: originalPoint withAttributes: attributes];
}

How can I refresh the screen immediately when the value of [otherObject stringToDisplay] has been changed?