Open Radar

 
Summary:
When creating a derived font descriptor with a font family, existing traits such as italic or bold are overwritten or ignored. This can be very confusing. If the behavior is somehow deemed to be correct, then the documentation for [UIFontDescriptor fontDescriptorWithFamily] should be updated to describe this behavior.

Steps to Reproduce:
var wrongFontDescriptor = UIFontDescriptor()
wrongFontDescriptor = wrongFontDescriptor.withSymbolicTraits([.traitItalic])!
wrongFontDescriptor = wrongFontDescriptor.withFamily("Avenir")
var wrongFont = UIFont(descriptor: wrongFontDescriptor, size: 12)

Expected Results:
I Expect the resulting font to be “Avenir-BookOblique”

Actual Results:
Instead, the resulting font is "Avenir-Book"

Version:
11.0

Notes:
The correct font can be achieved by changing the order of calls building up the font descriptor:

var rightFontDescriptor = UIFontDescriptor()
rightFontDescriptor = rightFontDescriptor.withFamily("Avenir")
rightFontDescriptor = rightFontDescriptor.withSymbolicTraits([.traitItalic])!
var rightFont = UIFont(descriptor: rightFontDescriptor, size: 12)
rightFont.fontName