Hacky way to get a custom nav bar height

HackyNavBar

#import "SBBaseNavigationBar.h"



@interface SBBaseNavigationBar (iOS11HacksPrivate)
@property (nullable, nonatomic, readonly) UIView *navigationBarContentView;
@end



@implementation SBBaseNavigationBar

@dynamic promptViewHeight;

#pragma mark - Initialization

- (instancetype)initWithNavigationBarHeight:(CGFloat)height {
    self = [super initWithFrame:CGRectZero];
    if (self) {
        [self sb_navigationBarCommonInitWithNavigationBarHeight:height];
    }
    return self;
}

- (instancetype)initWithFrame:(CGRect)frame {
    return [self initWithNavigationBarHeight:60.0];
}

- (instancetype)initWithCoder:(NSCoder *)aDecoder {
    self = [super initWithCoder:aDecoder];
    if (self) {
        [self sb_navigationBarCommonInitWithNavigationBarHeight:60.0];
    }
    return self;
}

- (void)sb_navigationBarCommonInitWithNavigationBarHeight:(CGFloat)height {
    // enforce minimum height
    if (height < SBBaseNavigationBar.minimumBarHeight) {
        height = SBBaseNavigationBar.minimumBarHeight;
    }
    
    // defaults
    _navigationBarHeight = height;
}


#pragma mark - Setters

- (void)setNavigationBarHeight:(CGFloat)navigationBarHeight {
    if (navigationBarHeight < SBBaseNavigationBar.minimumBarHeight) {
        navigationBarHeight = SBBaseNavigationBar.minimumBarHeight;
    }
    
    _navigationBarHeight = navigationBarHeight;
    [self setNeedsLayout];
}


#pragma mark - Getters

+ (CGFloat)minimumBarHeight {
    return 44.0;
}


#pragma mark - Layout

- (void)setBounds:(CGRect)bounds {
    bounds.size.height = self.navigationBarHeight;
    [super setBounds:bounds];
}

- (void)setFrame:(CGRect)frame {
    //when nav is pushed modally, the navigationbar height isn't correct for the onscreen
    //animation, and only takes the correct height once the animation is correct
    //this forces the frame to adhere to the set navigationBarHeight for all instances
    frame.size.height = self.navigationBarHeight;
    
    // if we're adjusting the nav bar's layout to take the status bar into account, ensure the nav bar's origin.y is always at the bottom of the status bar.
    // Works around an issue when presenting a full screen modal on compact where the nav bar's height is set correctly, but the
    // origin is at 0
    if (@available(iOS 11.0, *)) {
        if (self.adjustsLayoutForStatusBar) {
            frame.origin.y = CGRectGetHeight(UIApplication.extensionSafeSharedApplication.statusBarFrame);
        }
    }
    
    [super setFrame:frame];
}

- (void)setCenter:(CGPoint)center {
    if (@available(iOS 11.0, *)) {
        center.y = (self.navigationBarHeight / 2) + self.centerOffset;
    }
    
    [super setCenter:center];
}

- (void)layoutSubviews {
    [super layoutSubviews];
    
    UIView *backgroundView = self.subviews.firstObject;
    CGRect backgroundFrame = backgroundView.frame;
    
    if (@available(iOS 11.0, *)) {
        backgroundFrame.size.height = self.navigationBarHeight - CGRectGetMinY(backgroundFrame);
        backgroundView.frame = backgroundFrame;
        
        [self overrideNavigationContentViewLayout];
    }    
}

- (CGSize)sizeThatFits:(CGSize)size {
    CGSize aSize = [super sizeThatFits:size];
    aSize.height = self.navigationBarHeight;
    return aSize;
}

@end


@implementation SBBaseNavigationBar (iOS11Hacks)

- (void)overrideNavigationContentViewLayout {
    [self.navigationBarContentView.layer removeAnimationForKey:@"position"];
    
    CGFloat statusBarInset = CGRectGetHeight(UIApplication.sharedApplication.statusBarFrame);
    CGFloat contentViewOriginY = ((self.navigationBarHeight - SBBaseNavigationBar.minimumBarHeight - statusBarInset) / 2);
        
    CGRect contentViewFrame = self.navigationBarContentView.frame;
    contentViewFrame.origin.y = contentViewOriginY;
    self.navigationBarContentView.frame = contentViewFrame;
}

@end


@implementation SBBaseNavigationBar (iOS11HacksPrivate)

- (UIView *)navigationBarContentView {
    UIView *contentView = [self.subviews filteredArrayUsingPredicate:[NSPredicate predicateWithBlock:^BOOL(UIView *evaluatedObject, NSDictionary<NSString *,id> *bindings) {
        return [evaluatedObject isKindOfClass:NSClassFromString(@"_UINavigationBarContentView")];
    }]].firstObject;
    
    return contentView;
}

@end