【iOS】UILabel多行文本的高度计算

平时这些代码用的时候，总是要搜索查阅，自己索性整理下记一笔，节约生命。

实现是直接给NSString类添加一个分类，并添加了计算文本高度的两个方法：

声明代码：

#import <Foundation/Foundation.h>

@interface NSString (Size)

/**
 * 计算单行文本的高度
 */
- (CGFloat)heightWithLabelFont:(UIFont *)font;
/**
 * 计算多行文本的高度
 */
- (CGFloat)heightWithLabelFont:(UIFont *)font withLabelWidth:(CGFloat)width;
@end

具体的实现代码：

#import "NSString+Size.h"

@implementation NSString (Size)

- (CGFloat)heightWithLabelFont:(UIFont *)font withLabelWidth:(CGFloat)width {
    CGFloat height = 0;
    
    if (self.length == 0) {
        height = 0;
    } else {
        NSDictionary *attribute = @{NSFontAttributeName:font};
        CGSize rectSize = [self boundingRectWithSize:CGSizeMake(width, MAXFLOAT)
                                            options:NSStringDrawingTruncatesLastVisibleLine|
                                                    NSStringDrawingUsesLineFragmentOrigin|
                                                    NSStringDrawingUsesFontLeading
                                         attributes:attribute
                                            context:nil].size;
        height = rectSize.height;
    }
    return height;
}

- (CGFloat)heightWithLabelFont:(UIFont *)font {
    CGFloat height = 0;
    if (self.length == 0) {
        height = 0;
    }else{
        CGSize rectSize = [self sizeWithAttributes:@{NSFontAttributeName:font}];
        height = rectSize.height;
    }
    return height;
}

@end