Format contents of NSMutableArray for .csv file

Question

I have a picture slideshow app which allows the user to rate 3 images. The ratings get stored in a NSMutableArray called rated like this:

    2014-01-06 07:10:23.040 SlideShowSurvey[50425:70b] (
    1, <-- Rating for Picture 1
    2, <-- Rating for Picture 2
    3  <-- Rating for Picture 3
)

This is then saved to a .csv file using the following code:

-(void)saveRatings
{
    NSString *picRatings = [NSString stringWithFormat:@"%@, \n",self.rated];
    // Find documents directory
    NSString *docPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSString *survey = [docPath stringByAppendingPathComponent:@"pictureRatings.csv"];
    // Create new file if none exists
    if (![[NSFileManager defaultManager] fileExistsAtPath:survey])
    {
        [[NSFileManager defaultManager] createFileAtPath:survey contents:nil attributes:nil];
    }
    NSFileHandle *fileHandle = [NSFileHandle fileHandleForUpdatingAtPath:survey];
    [fileHandle seekToEndOfFile];
    [fileHandle writeData:[picRatings dataUsingEncoding:NSUTF8StringEncoding]];
    [fileHandle closeFile];
}

I can then display the results of the .csv file to a UITextView, though it displays it exactly how the array is structured. For example, multiple results display as:

(
    1,
    2,
    3 
),
(
    1,
    2,
    3 
),
(
    1,
    2,
    3 
)

Is there a way I am able to format the array so that it is saved as 1,2,3? And would I be able to add a column header like Picture 1, Picture 2, Picture 3? For example, I would like to display results on the UITextView something like:

Picture 1, Picture 2, Picture 3
1,2,3
1,2,3
1,2,3

I've tried searching but can't seem to find this answer. Any help is appreciated! Thanks.

Edit: I have solved this thanks to jrturton's solution, using the following code:

        // Set column titles for .csv
    NSArray *columnTitleArray = @[@"Picture 1", @"Picture 2", @"Picture 3"];

    NSString *columnTitle = [columnTitleArray componentsJoinedByString:@","];
    NSString *columnTitleToWrite = [columnTitle stringByAppendingString:@"\n"];

    // Separate ratings into cells
    NSString *picRatings = [rated componentsJoinedByString:@","];
    NSString *picRatingsToWrite = [picRatings stringByAppendingString:@"\n"];

    // Find documents directory
..

Then adding this to the method to make sure column headers are only set when a new file is created:

    // Create new file if none exists
    if (![[NSFileManager defaultManager] fileExistsAtPath:survey])
    {
        [[NSFileManager defaultManager] createFileAtPath:survey contents:nil attributes:nil];

        // Set title for new file
        NSFileHandle *fileHandle = [NSFileHandle fileHandleForUpdatingAtPath:survey];
        [fileHandle writeData:[columnTitleToWrite dataUsingEncoding:NSUTF8StringEncoding]];
    }
..

Answer 1

Here is a much easier way:

NSMutableString *csv = [NSMutableString string];

NSString *label = ...;

[csv appendFormat:@"%@,\n", label];

NSNumber *keyNum = ...;

[csv appendFormat:@"%d,%d\n", [keyNum intValue], [countNum intValue]];

NSString *filename = @"counts.csv";

NSError *error; 

[csv writeToFile:filename atomically:YES encoding:NSUTF8StringEncoding error:&error];

Answer 2

使用此解析器并将数据放入数组，并查看如何将数据用于UITabelViewCell https://github.com/davedelong/CHCSVParser

Answer 3

NSMutableString *csv = [NSMutableString string];

NSString *label = @"\n";

[csv appendFormat:@",", label];

NSString *picRatings = [rated componentsJoinedByString:csv];

I'm not sure what you expect appendFormat to be doing in the above code, this will probably be raising a warning since label is not used. You don't need a mutable string in this case either.

To get the contents of an array separated by commas, do this:

NSString *picRatings = [rated componentsJoinedByString:@","];

You also need to add a new line to the end of this string, so you'd want:

NSString *picRatingsToWrite = [picRatings stringByAppendingString:@"\n"];

Write this string to your file and you should be fine.