iOS 7 dynamic UILabel frame adjustment for a given NSString and UIFont using boundingRectWithSize:options:attributes:context:.

iOS-7-boundingRectWithSize-options-attributes-context.m

NSString* string = @"Hello World"; 

UIFont *font = [UIFont fontWithName:@"Helvetica-BoldOblique" size:21];

CGSize constraint = CGSizeMake(300,NSUIntegerMax);

NSDictionary *attributes = @{NSFontAttributeName: font};

CGRect rect = [string boundingRectWithSize:constraint 
                                   options:(NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading)  
                                attributes:attributes 
                                   context:nil];

// Construct your label

UILabel* label = [[UILabel alloc] initWithFrame:rect];

[label setText:string];
 
[label setTextAlignment:NSTextAlignmentRight];

label.lineBreakMode = NSLineBreakByWordWrapping;

label.numberOfLines = 0;

[label setFont:font];

It does not work. Since lineBreakMode of label is WordWrapping, It does not give the expected result..
It Only works for CharWrapping

@vikipeter is there any way that it can be made to work with WordWrapping?

@fatuhoku To make it work with lineBreakMode, Add Paragraph style to the attributes

NSMutableParagraphStyle *style = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
[style setLineBreakMode:NSLineBreakByWordWrapping];

CGSize size = [string boundingRectWithSize:CGSizeMake(YOUR_WIDTH , NSUIntegerMax) options:(NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading) attributes:@{ NSForegroundColorAttributeName: [UIColor blackColor], NSFontAttributeName:[UIFont fontWithName:font size:fontSize], NSParagraphStyleAttributeName : style} context:nil].size;