IOS 文件，数据的读写

获取到 file 到名字方法

 NSArray *myPaths=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

//NSDocumentDirectory  是表示沙盒里 document 文件夹的列表

//NSDocumentionDirectory  是 获取 沙盒里 library 里 documention里的文件夹列表

    NSString *path=[myPaths objectAtIndex:0]; // objectAtIndex : 为document 的文件列表

    NSString *filename=[path stringByAppendingPathComponent:@"properties.plist"];

-(IBAction)save:(id)sender

{

    NSArray *myPaths=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

    NSString *path=[myPaths objectAtIndex:0];

    NSString *filename=[path stringByAppendingPathComponent:@"properties.plist"];

    NSMutableArray *array=[[NSMutableArray alloc] init];

    [array addObject:txt_name.text];

    [array addObject:txt_class.text];

    [array addObject:txt_id.text];

    [array writeToFile:filename atomically:YES];

    NSLog(@"come here");

}

-(IBAction)read:(id)sender

{

    NSArray *mypaths=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

    NSString *path=[mypaths objectAtIndex:0];

    NSString *filename=[path stringByAppendingPathComponent:@"properties.plist"];

    if([[NSFileManager defaultManager] fileExistsAtPath:filename])

    {

        NSLog(@"it‘s ok");

        NSMutableArray *array=[[NSMutableArray alloc] initWithContentsOfFile:filename];

        txt_name.text=[array objectAtIndex:0];

        txt_class.text=[array objectAtIndex:1];

        txt_id.text=[array objectAtIndex:2];

    }

}