IOS7中自动计算label的宽度和高度的方法

 #import "ViewController.h"

 @implementation ViewController

 - (void)viewDidLoad {
     [super viewDidLoad];

     //根据固定的宽度计算 计算label的高度
     [self sizeToLabelHeight];

     //根据固定的高度 计算label的宽度
     [self sizeToLabelWidth];

 }

 /**
  *  自动计算label的宽度  前提高度固定
  *
  */
 - (void)sizeToLabelWidth
 {
     UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(, , , )];
     label.textColor = [UIColor whiteColor];
     label.font = [UIFont systemFontOfSize:];
     label.numberOfLines = ; //这个属性 一定要设置为0   0表示自动换行   默认是1 不换行
     label.backgroundColor = [UIColor blackColor];
     label.textAlignment = NSTextAlignmentLeft;
     NSString *str = @"fsdfsfnksdfjsdkhfjksdhfjdolfsdfsfnksdfjsdkhfjksdhfjsdkhfjksdhfjdojdol";

     //第一种方式
     //    CGSize size = [str sizeWithFont:label.font constrainedToSize: CGSizeMake(MAXFLOAT,label.frame.size.height) lineBreakMode:NSLineBreakByWordWrapping];

     //第二种方式

     NSMutableDictionary *attrs = [NSMutableDictionary dictionary];
     attrs[NSFontAttributeName] = [UIFont systemFontOfSize:];

     CGSize size =  [str boundingRectWithSize:CGSizeMake( MAXFLOAT,label.frame.size.height) options:NSStringDrawingUsesLineFragmentOrigin attributes:attrs context:nil].size;

     label.frame = CGRectMake(, , size.width, );
     label.text = str;

     [self.view addSubview:label];
 }

 /**
  *  自动计算label的高度  前提 ：宽度固定
  */
 - (void)sizeToLabelHeight
 {

     UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(, , , )];
     label.textColor = [UIColor whiteColor];
     label.font = [UIFont systemFontOfSize:];
     label.numberOfLines = ;//这个属性 一定要设置为0   0表示自动换行   默认是1 不换行
     label.backgroundColor = [UIColor blackColor];
     label.textAlignment = NSTextAlignmentLeft;

     NSString *str = @"fsdfsfnksdfjsdkhfjksdhfjdolfsdfsfnksdfjsdkhfjksdhfjsdkhfjksdhfjdojdol";

     //第一种方式
     //    CGSize size = [str sizeWithFont:label.font constrainedToSize: CGSizeMake(label.frame.size.width, MAXFLOAT) lineBreakMode:NSLineBreakByWordWrapping];

     //第二种方式
     NSMutableDictionary *attrs = [NSMutableDictionary dictionary];
     attrs[NSFontAttributeName] = [UIFont systemFontOfSize:];

     CGSize size =  [str boundingRectWithSize:CGSizeMake(label.frame.size.width, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin attributes:attrs context:nil].size;

     label.frame = CGRectMake(, , , size.height);
     label.text = str;

     [self.view addSubview:label];
 }

 @end