[IOS自訂工具類之緩衝助手類]CacheHelper

[plain] #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  [plain]  #import "CacheHelper.h"  [plain] view plaincopy@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];      //建立緩衝時間控制檔案      [dataExpires writeToFile:[[self getTempPath:key] stringByAppendingFormat:@"%@",@".expires"] atomically:NO];      //建立快取檔案，寫入緩衝      [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{    }  //擷取臨時檔案目錄  + (NSString *)getTempPath:(NSString*)key{      NSString *tempPath = NSTemporaryDirectory();      return [tempPath stringByAppendingPathComponent:key];  }  //判斷檔案是否存在  + (BOOL)fileExists:(NSString *)filepath{      NSFileManager *fileManager = [NSFileManager defaultManager];      return [fileManager fileExistsAtPath:filepath];  }    //判斷是否到期  + (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