Not all system fonts are supported

[ArniDexian]

The docs saying:

FontName - A font name. See available values here. Can also be one of the following:
system
boldSystem
italicSystem
blackSystem
heavySystem
lightSystem
mediumSystem
semiboldSystem
thinSystem
ultraLightSystem

But, only some types are supported:

[NUISettings.m, line 202]
+ (UIFont*)getFontWithClass:(NSString*)className baseFont:(UIFont *)baseFont
{
    NSString *propertyName;
    CGFloat fontSize;
    UIFont *font = nil;
...
    propertyName = @"font-name";
    
    if ([self hasProperty:propertyName withClass:className]) {
        NSString *fontName = [self get:propertyName withClass:className];
        
        if ([fontName isEqualToString:@"system"]) {
            font = [UIFont systemFontOfSize:fontSize];
        } else if ([fontName isEqualToString:@"boldSystem"]) {
            font = [UIFont boldSystemFontOfSize:fontSize];
        } else if ([fontName isEqualToString:@"italicSystem"]) {
            font = [UIFont italicSystemFontOfSize:fontSize];
        } else {
            font = [UIFont fontWithName:fontName size:fontSize];
        }
    } else {
        font = baseFont ? [baseFont fontWithSize:fontSize] : [UIFont systemFontOfSize:fontSize];
    }
    
    return font;
}

Moreover I think it would great to throw assert if some font is not found.

[ArniDexian]

Can be fixed by using [UIFont systemFontOfSize:fontSize weight:UIFontWeightSemibold/UIFontWeightHeavy etc];