如何获取 NSString 的大小

Question

A "quicky": how can I get the size (width) of a NSString?

I'm trying to see if the string width of a string to see if it is bigger than a given width of screen, case in which I have to "crop" it and append it with "...", getting the usual behavior of a UILabel. string.length won't do the trick since AAAAAAAA and iiiiii have the same length but different sizes (for example).

I'm kind of stuck.

Thanks a lot.

Answer 1

This is a different approach. Find out the minimum size of the text so that it won't wrap to more than one line. If it wraps to over one line, you can find out using the height.

You can use this code:

CGSize maximumSize = CGSizeMake(300, 9999);
NSString *myString = @"This is a long string which wraps";
UIFont *myFont = [UIFont fontWithName:@"Helvetica" size:14];
CGSize myStringSize = [myString sizeWithFont:myFont 
                           constrainedToSize:maximumSize 
                               lineBreakMode:self.myLabel.lineBreakMode];

300 is the width of the screen with a little space for margins. You should substitute your own values for font and size, and for the lineBreakMode if you're not using IB.

Now myStringSize will contain a height which you can check against the height of something you know is only 1 line high (using the same font and size). If it's bigger, you'll need to cut the text. Note that you should add a ... to the string before you check it again (adding the ... might push it over the limit again).

Put this code in a loop to cut the text, then check again for the correct height.

Answer 2

Use below method.

Objective-C

- (CGSize)findHeightForText:(NSString *)text havingWidth:(CGFloat)widthValue andFont:(UIFont *)font {
    CGSize size = CGSizeZero;
    if (text) {
        CGRect frame = [text boundingRectWithSize:CGSizeMake(widthValue, CGFLOAT_MAX) options:NSStringDrawingUsesLineFragmentOrigin attributes:@{ NSFontAttributeName:font } context:nil];
        size = CGSizeMake(frame.size.width, frame.size.height + 1);
    }
    return size;
}

Swift 3.0

func findHeight(forText text: String, havingWidth widthValue: CGFloat, andFont font: UIFont) -> CGSize {
    var size = CGSizeZero
    if text {
        var frame = text.boundingRect(withSize: CGSize(width: widthValue, height: CGFLOAT_MAX), options: .usesLineFragmentOrigin, attributes: [NSFontAttributeName: font], context: nil)
        size = CGSize(width: frame.size.width, height: frame.size.height + 1)
    }
    return size
}

Answer 3

You need to use Core Graphics to measure the string, as rendered in your specified font and size. See the answers to Measuring the pixel width of a string for a walkthrough.

Answer 4

sizeWithFont:constrainedToSize:lineBreakMode 

is deprecated now. Use below code snippet,

UIFont *font=[UIFont fontWithName:@"Arial" size:16.f];

NSString *name = @"APPLE";

CGSize size = [name sizeWithAttributes:@{NSFontAttributeName:font}];

Answer 5

For whatever its worth --- I think the OP takes the wrong way to get there... if the measurement of width only serves to find the place where text should be clipped, and followed by ellipsis --- then OP should be aware of that this facility is implemented in all Text Views in Cocoa...

Pay attention to this enumeration:

typedef NS_ENUM(NSUInteger, NSLineBreakMode) {
    NSLineBreakByWordWrapping = 0,         // Wrap at word boundaries, default
    NSLineBreakByCharWrapping,        // Wrap at character boundaries
    NSLineBreakByClipping,        // Simply clip
    NSLineBreakByTruncatingHead,    // Truncate at head of line: "...wxyz"
    NSLineBreakByTruncatingTail,    // Truncate at tail of line: "abcd..."
    NSLineBreakByTruncatingMiddle    // Truncate middle of line:  "ab...yz"
} API_AVAILABLE(macos(10.0), ios(6.0), watchos(2.0), tvos(9.0));

By setting the line breaking mode of your text-field or text view to NSLineBreakByTruncatingTail , you'll achieve what you want, and probably at higher quality, without implementing yourself.