【IOS自定义工具类之缓存助手类】CacheHelper

 #import <Foundation/Foundation.h>


 @interface CacheHelper : NSObject {

 }

 + (void) setObject:(NSData *) data forKey:(NSString *) key withExpires:(int) expires;
 + (NSData *) get:(NSString *) key;
 + (void) clear;
 + (NSString *)getTempPath:(NSString*)key;
 + (BOOL)fileExists:(NSString *)filepath;
 + (BOOL)isExpired:(NSString *) key;

 @end

 #import "CacheHelper.h"

 @implementation CacheHelper

 + (void) setObject:(NSData *) data forKey:(NSString *) key withExpires:(int) expires{
     NSDate *dt = [NSDate date];
     double now = [dt timeIntervalSince1970];
     NSMutableString *expiresString = [[NSMutableString alloc] init];
     NSData *dataExpires = [[expiresString stringByAppendingFormat:@"%f",now+expires] dataUsingEncoding:NSUTF8StringEncoding];
     [expiresString release];
     //创建缓存时间控制文件
     [dataExpires writeToFile:[[self getTempPath:key] stringByAppendingFormat:@"%@",@".expires"] atomically:NO];
     //创建缓存文件，写入缓存
     [data writeToFile:[self getTempPath:key] atomically:NO];
 }

 + (NSData *) get:(NSString *) key{
     if(![self fileExists:[self getTempPath:key]] || [self isExpired:[self getTempPath:key]]){
         NSLog(@"no cache");
         return nil;
     }

     NSData *data = [NSData dataWithContentsOfFile:[self getTempPath:key]];
     return data;
 }

 + (void) clear{

 }
 //获取临时文件目录
 + (NSString *)getTempPath:(NSString*)key{
     NSString *tempPath = NSTemporaryDirectory();
     return [tempPath stringByAppendingPathComponent:key];
 }
 //判断文件是否存在
 + (BOOL)fileExists:(NSString *)filepath{
     NSFileManager *fileManager = [NSFileManager defaultManager];
     return [fileManager fileExistsAtPath:filepath];
 }

 //判断是否过期
 + (BOOL)isExpired:(NSString *) filepath{
     NSData *data = [NSData dataWithContentsOfFile:[filepath stringByAppendingFormat:@"%@",@".expires"]];
     NSString *expires = [[NSString alloc] initWithData:data  encoding:NSUTF8StringEncoding];
     double exp = [expires doubleValue];
     [expires release];
     NSDate *dt = [NSDate date];
     double value = [dt timeIntervalSince1970];

     if(exp > value){

         return NO;
     }
     return YES;
 }

 @end