IOS中的NSFileManager

Question

- (void)viewDidLoad
{
    [super viewDidLoad];

    NSFileManager * fileManager =[[NSFileManager alloc]init];
    NSArray  *Apath=[fileManager URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask];
    NSString *FilePath=[[Apath objectAtIndex:0] absoluteString];
    NSString *TEST =[FilePath stringByAppendingPathComponent:@"test10.txt"];
    BOOL flage =[[NSFileManager  defaultManager] fileExistsAtPath:TEST];

    if (flage)
    {
        NSLog(@"It's exist ");
    }
    else
    {
        NSLog(@"It is not here yet ");
        NSData * data =[[NSData alloc]initWithContentsOfURL:[NSURL URLWithString:@"www.google.com"]];
        [data writeToFile:TEST atomically:YES];
    }
}

I'm just trying to create a text file , it always give me "It is not here yet" Anything wrong with the code ??

Answer 1

You haven't created a file, you have only created a file path: you need to write a file to that path.

   //after these lines ... (I've improved your variable names) 
NSArray  *paths=[fileManager URLsForDirectory:NSDocumentDirectory 
                                    inDomains:NSUserDomainMask];
NSString *filePath=[[paths objectAtIndex:0] absoluteString];
filePath =[filePath stringByAppendingPathComponent:@"test10.txt"];


   //try this
NSString* fileContent = @"some text to save in a file";
BOOL success = [fileContent writeToFile:filePath 
              atomically:YES 
                encoding:NSUTF8StringEncoding 
                   error:nil]

But watch out - file existence tests come with a warning from Apple:

Note: Attempting to predicate behavior based on the current state of the file system or a particular file on the file system is not recommended. Doing so can cause odd behavior or race conditions. It's far better to attempt an operation (such as loading a file or creating a directory), check for errors, and handle those errors gracefully than it is to try to figure out ahead of time whether the operation will succeed.