15.文件管理一

1.概述

1. NSFileManager类主要是对文件的操作(删除, 修改, 移动, 复制等)
2. NSFileHandle类主要是对文件内容进行读取和写入操作, 步骤为:
   1) 创建一个NSFileHandle对象
   2) 对打开的文件进行I/O操作
   3)关闭文件按
3. 可以使用NSFileHandle做文件的断点续传
4. NSFileHandle只能读写文件, 不能创建文件, 创建文件使用NSFileManager.

2.NSFileHandle常用的方法

+ (instancetype)fileHandleForReadingAtPath:(NSString *)path;//打开一个文件准备读取+ (instancetype)fileHandleForWritingAtPath:(NSString *)path;//打开一个文件准备写入+ (instancetype)fileHandleForUpdatingAtPath:(NSString *)path;//打开一个文件准备更新@property(readonly, copy)NSData *availableData;//从设备或通道返回可用数据- (NSData *)readDataToEndOfFile;//从当前节点读取到文件末尾- (NSData *)readDataOfLength:(NSUInteger)length;//从当前节点开始读取指定的长度数据- (void)writeData:(NSData *)data;//写入数据@property (readonly)unsigned long long offsetInFile;//获取当前文件的偏移量- (unsigned long long)seekToEndOfFile;//跳到文件末尾- (void)seekToFileOffset:(unsigned long long)offset;//跳到指定文件的偏移量- (void)closeFile;//关闭文件

3.简单运用

/**1.追加数据****/NSString *homePath = NSHomeDirectory();NSString *filePath = [homePath stringByAppendingPathComponent:@"phone/cellPhone.text"];NSFileHandle *fileHandle = [NSFileHandle fileHandleForUpdatingAtPath:filePath];//追加数据[fileHandle seekToEndOfFile];NSString *str = @"追加的数据";NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding];[fileHandle writeData:data];[fileHandle closeFile];

/**2.定位读取数据**/NSString *homePath = NSHomeDirectory();NSString *filePath = [homePath stringByAppendingPathComponent:@"phone/cellPhone.text"];NSFileHandle *fileHandle = [NSFileHandle fileHandleForReadingAtPath:filePath];NSUInteger length = [fileHandle availableData].length;[fileHandle seekToFileOffset:length/2];NSData *data = [fileHandle readDataToEndOfFile];NSString *str = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];NSLog(@"

//***3.复制文件***NSString *homePath = NSHomeDirectory();NSString *filePath = [homePath stringByAppendingPathComponent:@"phone/cellPhone.text"];NSString *tagetPath = [homePath stringByAppendingPathComponent:@"cellPhone_bak.text"];NSFileManager *fileManager = [NSFileManager defaultManager];BOOL success = [fileManager createFileAtPath:tagetPath contents:nil attributes:nil];if (success) {    NSLog(@"create success");}NSFileHandle *outFileHandle = [NSFileHandle fileHandleForWritingAtPath:tagetPath];NSFileHandle *inFileHandle = [NSFileHandle fileHandleForReadingAtPath:filePath];//[inFileHandle availableData];NSData *data = [inFileHandle readDataToEndOfFile];[outFileHandle writeData:data];[outFileHandle closeFile];[inFileHandle closeFile];

4.实例一

创建一个Dage.text文件, 获取当前的日期, 将日期格式为”2015/08/02 03: 20:00” 的形式. 然后一秒钟记录一次, 将新的时间存入到文件中.
WriteDate.h和WriteDate.m文件

#import <Foundation/Foundation.h>@interface WriteDate : NSObject- (void)runWrite;@end

#import "WriteDate.h"@implementation WriteDate- (void)runWrite {    NSFileManager *fileManager = [NSFileManager defaultManager];    NSString *path = NSHomeDirectory();    NSString *filePath = [path stringByAppendingPathComponent:@"Date.text"];    //创建文件    BOOL success = [fileManager createFileAtPath:filePath contents:nil attributes:nil];    if (success) {        NSLog(@"create success");    }    //写文件对象    NSFileHandle *fileHandle = [NSFileHandle fileHandleForWritingAtPath:filePath];    [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(timerAction:) userInfo:fileHandle repeats:YES];}- (void)timerAction:(NSTimer *)timer{    static int n = 0;    NSFileHandle *fileHandle = timer.userInfo;    //跳到文件的末尾    [fileHandle seekToEndOfFile];    NSDate *nowDate = [NSDate date];    NSDateFormatter *dateformate = [[NSDateFormatter alloc] init];    //设置日期的格式    [dateformate setDateFormat:@"yyyy/MM/dd HH:mm:ss"];    //将日期对象格式为字符串    NSString *datestring = [dateformate stringFromDate:nowDate];    [dateformate release];    datestring = [datestring stringByAppendingString:@"\n"];    NSData *data = [datestring dataUsingEncoding:NSUTF8StringEncoding];    [fileHandle writeData:data];    if (n == 10) {        [timer invalidate];        [fileHandle closeFile];//关闭文件    }    n++;}@end

main.m文件

WriteDate *writeDate = [[WriteDate alloc] init];[writeDate runWrite];[writeDate release];

5.实例二

复制一个大型文件, 为了节约内存, 每次只读取500个字节
main.m文件

NSString *homePath = NSHomeDirectory();//要复制的源文件路径NSString *srcPath = [homePath stringByAppendingPathComponent:@"youdao.pkg"];//目标文件路径NSString *tagetPath = [homePath stringByAppendingPathComponent:@"yd.pkg"];NSFileManager *fileManager = [NSFileManager defaultManager];//创建目标文件BOOL success = [fileManager createFileAtPath:tagetPath contents:nil attributes:nil];if (success) {    NSLog(@"create success");}//读取文件对象NSFileHandle *inFile = [NSFileHandle fileHandleForReadingAtPath:srcPath];//写文件对象NSFileHandle *outFile = [NSFileHandle fileHandleForWritingAtPath:tagetPath];//获取文件的属性NSDictionary *fileAttri = [fileManager attributesOfItemAtPath:srcPath error:nil];//获取文件的大小NSNumber *fileSizeNum = [fileAttri objectForKey:NSFileSize];BOOL isEnd = YES;NSInteger readSize = 0;     //已经读取的文件大小NSInteger fileSize = [fileSizeNum longValue];   //文件的总大小NSAutoreleasePool *pool = nil;int n = 0;NSLog(@"开始复制....");while (isEnd) {    if (n % 10 == 0) {        [pool release];        pool = [[NSAutoreleasePool alloc] init];    }    //计算剩下未读文件的大小    NSInteger subLeng = fileSize - readSize;    NSData *data = nil;    //如果剩余文件大小小于5000，则将剩下的数据全都读完，并且不再循环读取了    if (subLeng < 5000) {        isEnd = NO; //跳出循环        data = [inFile readDataToEndOfFile]; //读取剩下的数据    } else {        //读取5000个字节        data = [inFile readDataOfLength:5000];        //累加读取的大小        readSize += 5000;        [inFile seekToFileOffset:readSize];    }    //写入数据    [outFile writeData:data];    n++;}//关闭文件[outFile closeFile];NSLog(@"文件复制成功");