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(100, 100, 100, 100)];
    label.textColor = [UIColor whiteColor];
    label.font = [UIFont systemFontOfSize:13];
    label.numberOfLines = 0; //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:13];
    
    CGSize size =  [str boundingRectWithSize:CGSizeMake( MAXFLOAT,label.frame.size.height) options:NSStringDrawingUsesLineFragmentOrigin attributes:attrs context:nil].size;
    
    label.frame = CGRectMake(5, 0, size.width, 100);
    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(100, 100, 100, 100)];
    label.textColor = [UIColor whiteColor];
    label.font = [UIFont systemFontOfSize:13];
    label.numberOfLines = 0;//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:13];
    
    CGSize size =  [str boundingRectWithSize:CGSizeMake(label.frame.size.width, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin attributes:attrs context:nil].size;
    
    label.frame = CGRectMake(100, 100, 100, size.height);
    label.text = str;
    
    [self.view addSubview:label];
}


@end