【IOS自定义工具类之缓存助手类】CacheHelper

@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