文档目录中的读/写文件问题

Question

I am trying to write a very basic text string to my documents directory and work from there to later save other files etc.

I am currently stuck with it not writing anything into my Documents directory

(In my viewDidLoad )

NSArray *pathArray = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)
NSString *documentsDirectory = [pathArray objectAtIndex:0];

NSString *textPath = [documentsDirectory stringByAppendingPathComponent:@"file1.txt"];
NSString *text = @"My cool text message";

[[NSFileManager defaultManager] createFileAtPath:textPath contents:nil attributes:nil];
[text writeToFile:textPath atomically:NO encoding:NSUTF8StringEncoding error:NULL];
NSLog(@"Text file data: %@",[[NSFileManager defaultManager] contentsAtPath:textPath]);

This is what gets printed out:

2011-06-27 19:04:43.485 MyApp[5731:707] Text file data: (null)

If I try this, it also prints out null:

NSLog(@"My Documents: %@", [[NSFileManager defaultManager] contentsOfDirectoryAtPath:documentsDirectory error:NULL]);

What have I missed or am I doing wrong while writing to this file? Might it be something I need to change in my plist or some frameworks/imports needed?

Thanks

[EDIT] I passed a NSError object through the writeToFile and got this error:

Error: Error Domain=NSCocoaErrorDomain Code=512 "The operation couldn't be completed. (Cocoa error 512.)" UserInfo=0x12aa00 {NSFilePath=/var/mobile/Applications/887F4691-3B75-448F-9384-31EBF4E3B63E/Documents/file1.txt, NSUnderlyingError=0x14f6b0 "The operation couldn't be completed. Not a directory"}

[EDIT 2] This works fine on the simulator but not on my phone :/

Answer 1

Instead of using NSFileManager to get the contents of that file, try using NSString as such:

NSArray *pathArray = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)
NSString *documentsDirectory = [pathArray objectAtIndex:0];
NSString *textPath = [documentsDirectory stringByAppendingPathComponent:@"file1.txt"];
NSError *error = nil;
NSString *str = [NSString stringWithContentsOfFile:textPath encoding:NSUTF8StringEncoding error:&error];
if (error != nil) {
    NSLog(@"There was an error: %@", [error description]);
} else {
    NSLog(@"Text file data: %@", str);
}

Edit: Added error checking code.

Answer 2

How are you getting documentsDirectory ?

You should be using something like this:

NSArray *pathArray = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)

NSString *documentsDirectory = [pathArray lastObject];

Answer 3

You can also use NSFileHandle for writing data in file and save to document directory:

Create a variable of NSFileHandle

NSFileHandle *outputFileHandle;

use the prepareDataWrittenHandle function with passing file name in parameter with file extension

-(void)prepareDataWrittenHandle:(NSString *)filename
{
    //Create Path of file in document directory.
    NSString *documentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSString *outputFilePath = [documentsDirectory stringByAppendingPathComponent:filename];

    //Check file with above name is already exits or  not.
    if ([[NSFileManager defaultManager] fileExistsAtPath:outputFilePath] == NO) {
        NSLog(@"Create the new file at outputFilePath: %@", outputFilePath);

        //Create file at path.
        BOOL suc = [[NSFileManager defaultManager] createFileAtPath:outputFilePath
                                                           contents:nil
                                                         attributes:nil];
        NSLog(@"Create file successful?: %u", suc);
    }

    outputFileHandle = [NSFileHandle fileHandleForWritingAtPath:outputFilePath];
}

then write the string value to file as:

//Create a file
[self prepareDataWrittenHandle:@"file1.txt"];

//String to save in file
NSString *text = @"My cool text message";

//Convert NSString to NSData to save data in file.
NSData* data = [text dataUsingEncoding:NSUTF8StringEncoding]

//Write NSData to file
[_outputFileHandle writeData:data];

//close the file if written complete
[_outputFileHandle closeFile];

at the end of file written you should close the file.

You can also check the content written in file as NSString for debug point of view as mention above by @Glenn Smith:

NSString *documentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString *outputFilePath = [documentsDirectory stringByAppendingPathComponent:@"file1.txt"];

NSError *error;
NSString *str = [NSString stringWithContentsOfFile:outputFilePath encoding:NSUTF8StringEncoding error:&error];
if (error != nil) {
    NSLog(@"There was an error: %@", [error description]);
} else {
    NSLog(@"Text file data: %@", str);
}

Answer 4

Put an NSLog statement after every line where you are setting a variable's value, so that you can inspect those values. This should help you quickly pinpoint where things start to go wrong.

Answer 5

The problem got solved by setting a non standard Bundle ID in die info.plist

I used the Bundle ID from iTunes Connect for this specific app. Now everything works perfectly.