change subviews according to its superview frame - ios

Question

I have a custom UIView class
CustomView.m
- (instancetype)initWithString:(NSString *)aString {
self = [super init];
if (!self)
return nil;
[self setAutoresizesSubviews:YES];
UILabel *label = [[UILabel alloc] init];
label.frame = ({
CGRect frame = self.frame;
frame.origin.x = CGRectGetMinX(frame) + 50;
frame.origin.y = CGRectGetMinY(frame) + 20;
frame.size.width = CGRectGetWidth(frame) - 100;
frame.size.height = CGRectGetHeight(frame) - 40;
frame;
});
[label setText:aString];
[self addSubview:label];
return self;
}
ViewController.m
-(void)addCustomView {
CustomView *custom = [CustomView alloc] initWithString:#"abc"];
custom.frame = ({
CGRect frame = self.view.frame;
frame.origin.y = CGRectGetHeight(frame) - 100;
frame.size.height = 100;
frame;
});
[self.view addSubview: custom];
}
Here's the problem, I set frame of my CustomView after alloc init it.
Which means its frame is CGRectZero before I change it.
Therefore, the frame of UILabel is zero, too.
How can I change frame of my subviews after their superview's frame changed ? Like above.
Thanks.

Answer 1

You simply need to implement -layoutSubviews in your CustomView, and do your subview layout/frame calculation stuff in there. -layoutSubviews will get called when your CustomView's frame changes.
Edit for further clarification:
You could add a property for the label, or use a tag, so that you can access it it -layoutSubviews, something like this;
- (void)layoutSubviews
{
self.label.frame = ({
CGRect frame = self.frame;
frame.origin.x = CGRectGetMinX(frame) + 50;
frame.origin.y = CGRectGetMinY(frame) + 20;
frame.size.width = CGRectGetWidth(frame) - 100;
frame.size.height = CGRectGetHeight(frame) - 40;
frame;
});
}
Edit 2:
Of course, what you probably want to do as well is change your initialiser to include the frame, like so:
- (instancetype)initWithFrame:(CGRect)frame string:(NSString *)string
{
self = [super initWithFrame:frame];
if (self) {
// Do some stuff
}
return self;
}
That way, your view's frame is set when you first create the label. Implementing -layoutSubviews is still a good idea though, for any future frame changes/orientation changes etc.