43给UIView设置阴影

UIView *mView = [[UIView alloc] initWithFrame:CGRectMake(50, 50, 50, 50)];

[mView.layer setShadowColor:[[UIColor grayColor] CGColor]];

mView.backgroundColor = [UIColor yellowColor];;

[mView setClipsToBounds:NO];
[mView.layer setShadowOpacity:1.0];
[self.view addSubview:mView];
[mView.layer setShadowOffset:CGSizeMake(-20, 0)];