如何计算Objective-C字符串（NSString）中的行数？

Question

我想计算Objective-C中NSString的行数。

NSInteger lineNum = 0; 
    NSString *string = @"abcde\nfghijk\nlmnopq\nrstu"; 
    NSInteger length = [string length]; 
    NSRange range = NSMakeRange(0, length); 
    while (range.location < length) { 
     range = [string lineRangeForRange:NSMakeRange(range.location, 0)]; 
     range.location = NSMaxRange(range); 
     lineNum += 1; 
    } 

有没有更简单的方法？

Answer 1

好，一个不是很有效，但尼斯（ISH）寻找方法是

NSString *string = @"abcde\nfghijk\nlmnopq\nrstu"; 
NSInteger length = [[string componentsSeparatedByCharactersInSet: 
           [NSCharacterSet newlineCharacterSet]] count]; 

Answer 2

苹果公司建议使用此方法：

NSString *string; 
unsigned numberOfLines, index, stringLength = [string length]; 

for (index = 0, numberOfLines = 0; index < stringLength; numberOfLines++) 
    index = NSMaxRange([string lineRangeForRange:NSMakeRange(index, 0)]); 

见article。他们还解释了如何计算包装文本的行数。

Answer 3

如果要考虑到文本的宽度，你可以用TextKit（iOS7 +）做到这一点：

func numberOfLinesForString(string: String, size: CGSize, font: UIFont) -> Int { 
    let textStorage = NSTextStorage(string: string, attributes: [NSFontAttributeName: font]) 

    let textContainer = NSTextContainer(size: size) 
    textContainer.lineBreakMode = .ByWordWrapping 
    textContainer.maximumNumberOfLines = 0 
    textContainer.lineFragmentPadding = 0 

    let layoutManager = NSLayoutManager() 
    layoutManager.textStorage = textStorage 
    layoutManager.addTextContainer(textContainer) 

    var numberOfLines = 0 
    var index = 0 
    var lineRange : NSRange = NSMakeRange(0, 0) 
    for (; index < layoutManager.numberOfGlyphs; numberOfLines++) { 
     layoutManager.lineFragmentRectForGlyphAtIndex(index, effectiveRange: &lineRange) 
     index = NSMaxRange(lineRange) 
    } 

    return numberOfLines 
}