Replacement for Deprecated sizeWithFont: in iOS 7 and Thread Safety Considerations

Introduction

In iOS 7, the sizeWithFont: method was deprecated, necessitating a shift to more modern APIs. This article aims to dissect this change and offer practical alternatives.

Core Replacement Method: sizeWithAttributes:

The sizeWithAttributes: method accepts an NSDictionary parameter containing text attributes. To pass a font object, use the key NSFontAttributeName. Here is a basic example:

CGRect rawRect = {};
rawRect.size = [string sizeWithAttributes: @{
    NSFontAttributeName: [UIFont systemFontOfSize:17.0f],
}];
CGSize adjustedSize = CGRectIntegral(rawRect).size;

Note that the returned size may be fractional; it is recommended to use CGRectIntegral or the ceil function to adjust for accurate view sizing.

Thread Safety and Advanced Solution: boundingRectWithSize:

One reason for deprecating sizeWithFont: is its reliance on the UIStringDrawing library, which is not thread-safe. The boundingRectWithSize: method for NSAttributedString, introduced in iOS 6, offers a thread-safe alternative. Here is an example of converting old code:

Old code:

NSString *text = ...;
CGFloat width = ...;
UIFont *font = ...;
CGSize size = [text sizeWithFont:font 
               constrainedToSize:(CGSize){width, CGFLOAT_MAX}];

New code:

NSString *text = ...;
CGFloat width = ...;
UIFont *font = ...;
NSAttributedString *attributedText =
    [[NSAttributedString alloc] initWithString:text 
                                    attributes:@{NSFontAttributeName: font}];
CGRect rect = [attributedText boundingRectWithSize:(CGSize){width, CGFLOAT_MAX}
                                           options:NSStringDrawingUsesLineFragmentOrigin
                                           context:nil];
CGSize size = rect.size;
CGFloat height = ceilf(size.height);
CGFloat width  = ceilf(size.width);

This approach not only addresses the deprecation but also enhances application stability in multi-threaded environments.

Conclusion

Migrating to sizeWithAttributes: or boundingRectWithSize: is key to handling the deprecation of sizeWithFont: in iOS 7. Developers should choose the appropriate method based on application needs and handle fractional sizes to ensure compatibility.