简单计算字符串的高度

//
//  NSString+NSStringExt.h
//  UIFontSize
//
//  Created by mac on 15/11/14.
//  Copyright (c) 2015年 叶炯. All rights reserved.
//

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
@interface NSString (NSStringExt)

//对象方法
-(CGSize)sizeOfTextWithMaxSize:(CGSize)maxSize font:(UIFont *)font;

//类方法

+(CGSize)sizeWithText:(NSString * )text maxSize:(CGSize)maxSize font:(UIFont*)font;
@end

//
//  NSString+NSStringExt.m
//  UIFontSize
//
//  Created by mac on 15/11/14.
//  Copyright (c) 2015年 叶炯. All rights reserved.
//

#import "NSString+NSStringExt.h"

@implementation NSString (NSStringExt)

//实现减号方法
-(CGSize)sizeOfTextWithMaxSize:(CGSize)maxSize font:(UIFont *)font

{
    NSDictionary * attrs = @{NSFontAttributeName : font};
    return [self boundingRectWithSize:maxSize options:NSStringDrawingUsesLineFragmentOrigin attributes:attrs context:nil].size;



}
//实现类方法
+(CGSize)sizeWithText:(NSString *)text maxSize:(CGSize)maxSize font:(UIFont *)font
{
    //maxSize CGSize  宽不指定 ，高 MAXFLOAT
    return [text sizeOfTextWithMaxSize:maxSize font:font];

}




@end