使用Swift等效项更新Objective-C语法以使用未使用的静态

Question

I am stuck on translating a method from the following bit.

In original Objective-C, the method is:

+ (CGFloat)defaultFontSize
{
    CGFloat pointSize = 16.0;
    NSString *contentSizeCategory = [[UIApplication sharedApplication] preferredContentSizeCategory];
    pointSize += SLKPointSizeDifferenceForCategory(contentSizeCategory); //stucj here

    return pointSize;
}

In Swift, I have done the following so far:

let defaultFontSize: Float {
        get {
            let pointSize = 16.0
            let contentSizeCategory = UIApplication.shared.preferredContentSizeCategory
            //What do here for SLKPointSizeDifferenceForCategory?
     }
}

In particular, I don't know how to translate SLKPointSizeDifferenceForCategory , which is an unused static CGFloat :

__unused static CGFloat SLKPointSizeDifferenceForCategory(NSString *category)
{
    if ([category isEqualToString:UIContentSizeCategoryExtraSmall])                         return -3.0;
    if ([category isEqualToString:UIContentSizeCategorySmall])                              return -2.0;
    if ([category isEqualToString:UIContentSizeCategoryMedium])                             return -1.0;
    if ([category isEqualToString:UIContentSizeCategoryLarge])                              return 0.0;
    if ([category isEqualToString:UIContentSizeCategoryExtraLarge])                         return 2.0;
    if ([category isEqualToString:UIContentSizeCategoryExtraExtraLarge])                    return 4.0;
    if ([category isEqualToString:UIContentSizeCategoryExtraExtraExtraLarge])               return 6.0;
    if ([category isEqualToString:UIContentSizeCategoryAccessibilityMedium])                return 8.0;
    if ([category isEqualToString:UIContentSizeCategoryAccessibilityLarge])                 return 10.0;
    if ([category isEqualToString:UIContentSizeCategoryAccessibilityExtraLarge])            return 11.0;
    if ([category isEqualToString:UIContentSizeCategoryAccessibilityExtraExtraLarge])       return 12.0;
    if ([category isEqualToString:UIContentSizeCategoryAccessibilityExtraExtraExtraLarge])  return 13.0;
    return 0;
}

Any guidance is much appreciated.

Answer 1

That's just a function that returns a CGFloat :

func SLKPointSizeDifference(for category: UIContentSizeCategory) -> CGFloat {
    typealias c = UIContentSizeCategory // for the sake of reducing boilerplate below

    switch category {
    case c.extraSmall:                         return -3
    case c.small:                              return -2
    case c.medium:                             return -1
    case c.large:                              return 0
    case c.extraLarge:                         return 2
    case c.extraExtraLarge:                    return 4
    case c.extraExtraExtraLarge:               return 6
    case c.accessibilityMedium:                return 8
    case c.accessibilityLarge:                 return 10
    case c.accessibilityExtraLarge:            return 11
    case c.accessibilityExtraExtraLarge:       return 12
    case c.accessibilityExtraExtraExtraLarge:  return 13
    default:                                   return 0
    }
}

• __unused is just a flag that tells the compiler not to warn if that function is never used. See more here .

• static just limits the scope of that function's existence to the current file.

• UIContentSizeCategory is imported into Swift as a struct, which is more strongly typed than just using raw strings.

Answer 2

__unused only tells the compiler "don't warn me if I don't use this variable". , and in this context I believe that means no warning should be shown if the result of SLKPointSizeDifferenceForCategory goes unused.

As for the Slack SDK function you're trying to port , why not simply include SlackTextViewController in your bridging header and then you can pick up the original function like magic.