基础(一)：根据文字动态计算Label的高度

- (CGSize)sizeWithText:(NSString *)text textMaxWidth:(CGFloat)width textFont:(UIFont *)font {
    
    // 包装表示字体的字典
    NSDictionary *AttributeDict = @{NSFontAttributeName : font};
    
    CGSize size = CGSizeMake(width, MAXFLOAT);
    
    return [text boundingRectWithSize:size options:
            NSStringDrawingUsesLineFragmentOrigin |
            NSStringDrawingUsesFontLeading |
            NSStringDrawingTruncatesLastVisibleLine
                           attributes:AttributeDict context:nil].size;
    
}