ios 读写文件-复习篇

//创建文件管理器 NSFileManager   *fileManager   =   [ NSFileManager   defaultManager ] ; //获取路径 //参数NSDocumentDirectory要获取那种路径 NSArray   *paths   =   NSSearchPathForDirectoriesInDomains ( NSDocumentDirectory , NSUserDomainMask ,   YES ) ; NSString   *documentsDirectory   =   [ paths  objectAtIndex : 0 ] ;   //更改到待操作的目录下 [ fileManager  changeCurrentDirectoryPath : [ documentsDirectory  stringByExpandingTildeInPath ] ] ;   //创建文件fileName文件名称，contents文件的内容，如果开始没有内容可以设置为nil，attributes文件的属性，初始为nil [ fileManager  createFileAtPath : @"fileName"  contents :nil  attributes :nil ] ;   //删除待删除的文件 [ fileManager  removeItemAtPath : @"createdNewFile"  error :nil ] ; 写入数据： //获取文件路径NSString *path = [documentsDirectory stringByAppendingPathComponent:@"fileName"];//待写入的数据NSString *temp = @”Welcome to blog.iosxcode4.com”;int data0 = 100000;float data1 = 23.45f;//创建数据缓冲NSMutableData *writer = [[NSMutableData alloc] init];//将字符串添加到缓冲中[writer appendData:[temp dataUsingEncoding:NSUTF8StringEncoding]];//将其他数据添加到缓冲中[writer appendBytes:&data0 length:sizeof(data0)];[writer appendBytes:&data1 length:sizeof(data1)];//将缓冲的数据写入到文件中[writer writeToFile:path atomically:YES];[writer release]; 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 //获取文件路径 NSString   *path   =   [ documentsDirectory stringByAppendingPathComponent : @"fileName" ] ;   //待写入的数据 NSString   *temp   =   @ ” Welcome   to  blog . iosxcode4 . com ” ; int   data0   =   100000 ; float   data1   =   23.45f ;   //创建数据缓冲 NSMutableData   *writer   =   [ [ NSMutableData   alloc ]  init ] ;   //将字符串添加到缓冲中 [ writer  appendData : [ temp dataUsingEncoding :NSUTF8StringEncoding ] ] ;   //将其他数据添加到缓冲中 [ writer  appendBytes : & data0  length :sizeof ( data0 ) ] ; [ writer  appendBytes : & data1  length :sizeof ( data1 ) ] ;   //将缓冲的数据写入到文件中 [ writer  writeToFile :path  atomically :YES ] ; [ writer  release ] ; 读取数据： int gData0;float gData1;NSString *gData2;NSData *reader = [NSData dataWithContentsOfFile:path];gData2 = [[NSString alloc] initWithData:[reader subdataWithRange:NSMakeRange(0, [temp length])]encoding:NSUTF8StringEncoding];[reader getBytes:&gData0 range:NSMakeRange([temp length], sizeof(gData0))];[reader getBytes:&gData2 range:NSMakeRange([temp length] + sizeof(gData0), sizeof(gData1))];NSLog(@”gData0:%@ gData1:%i gData2:%f”, gData0, gData1, gData2); 1 2 3 4 5 6 7 8 9 10 11 int   gData0 ; float   gData1 ; NSString   *gData2 ;   NSData   *reader   =   [ NSData  dataWithContentsOfFile :path ] ; gData2   =   [ [ NSString   alloc ]  initWithData : [ reader  subdataWithRange :NSMakeRange ( 0 ,   [ temp  length ] ) ] encoding :NSUTF8StringEncoding ] ; [ reader  getBytes : & gData0  range :NSMakeRange ( [ temp  length ] ,   sizeof ( gData0 ) ) ] ; [ reader  getBytes : & gData2  range :NSMakeRange ( [ temp  length ]   +   sizeof ( gData0 ) , sizeof ( gData1 ) ) ] ;   NSLog ( @ ” gData0 : % @   gData1 : % i  gData2 : % f ” ,   gData0 ,   gData1 ,   gData2 ) ;