【iOS】UILabel多行文本的高度計算

平時這些代碼用的時候，總是要搜索查閱，自己索性整理下記一筆，節約生命。

實現是直接給NSString類添加一個分類，並添加了計算文本高度的兩個方法：

聲明代碼：

#import <Foundation/Foundation.h>

@interface NSString (Size)

/**
 * 計算單行文本的高度
 */
- (CGFloat)heightWithLabelFont:(UIFont *)font;
/**
 * 計算多行文本的高度
 */
- (CGFloat)heightWithLabelFont:(UIFont *)font withLabelWidth:(CGFloat)width;
@end

具體的實現代碼：

#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