Using a class method to create an NSArray

Once more I come to the Internet, hat in hand. :)

I'm attempting to use a class method to return a populated array containing other arrays as elements:

.h:

@interface NetworkData : NSObject {

}

    +(NSString*) getCachePath:(NSString*) filename;
    +(void) writeToFile:(NSString*)text withFilename:(NSString*) filePath;
    +(NSString*) readFromFile:(NSString*) filePath;
    +(void) loadParkData:(NSString*) filename;
    +(NSArray*) generateColumnArray:(int) column type:(NSString*) type filename:(NSString*) filename;

@end

.m:

#import "NetworkData.h"
#import "JSON.h"
#import "Utility.h"


@implementation NetworkData

+(NSString*) getCachePath:(NSString*) filename {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *cachePath = [NSString stringWithFormat:@"%@/%@", [paths objectAtIndex:0], filename];
    [paths release];
    return cachePath;
 }

+(void) writeToFile:(NSString*)text withFilename:(NSString*) filename {
    NSMutableArray *array = [[NSArray alloc] init];
    [array addObject:text];
    [array writeToFile:filename atomically:YES];
    [array release];
}

+(NSString*) readFromFile:(NSString*) filename {
    NSFileManager* filemgr = [[NSFileManager alloc] init];
    NSData* buffer = [filemgr contentsAtPath:filename];
    NSString* data = [[NSString alloc] initWithData开发者_如何学Go:buffer encoding:NSUTF8StringEncoding];
    [buffer release];
    [filemgr release];
    return data;
}

+(void) loadParkData:(NSString*) filename {
    NSString *filePath = [self getCachePath:filename];
    NSURL *url = [NSURL URLWithString:@"http://my.appserver.com"];
    NSData *urlData = [NSData dataWithContentsOfURL:url];
    [urlData writeToFile:filePath atomically:YES];
}

+(NSArray*) generateColumnArray:(int) column type:(NSString*) type filename:(NSString*) filename {
    //  NSLog(@"generateColumnArray called: %u %@ %@", column, type, filename);
    //  productArray = [[NSMutableArray alloc] init];
    //  NSString *filePath = [self getCachePath:filename];
    //  NSString *fileContent = [self readFromFile:filePath];
    //  NSString *jsonString = [[NSString alloc] initWithString:fileContent];
    //  NSDictionary *results = [jsonString JSONValue];
    //  NSArray *eventsArray = [results objectForKey:type];
    //  NSInteger* eventsArrayCount = [eventsArray count];
    //  NSInteger* a;

    //  for (a = 0; a < eventsArrayCount; a++) {
    //      NSArray *eventsColSrc = [eventsArray objectAtIndex:a];
    //      NSArray *blockArray = [eventsColSrc objectAtIndex:column];
    //      [productArray addObject:blockArray];
    //      [blockArray release];
    //  }

    //  [eventsArray release];
    //  [results release];
    //  [jsonString release];
    //  [fileContent release];
    //  [filePath release];

    //  [a release];
    //  [eventsArrayCount release];

    //  return productArray;
    }

-(void)dealloc {
    [super dealloc];
}

@end

.. and the call:

NSArray* dataColumn = [NetworkData generateColumnArray:0 type:@"eventtype_a" filename:@"data.json"];

The code within the method works (isn't pretty, I know - noob at work). It's essentially moot because just calling it (with no active code, as shown) causes the app to quit before the splash screen reveals anything else.

I'm betting this is a headslapper - many thanks for any knowledge you can drop.

If your app crashes, there's very likely a message in the console that tells you why. It's always helpful to include that message when seeking help.

One obvious problem is that your +generateColumnArray... method is supposed to return a pointer to an NSArray, but with all the code in the method commented out, it's not returning anything, and who-knows-what is being assigned to dataColumn. Try just adding a return nil; to the end of the method and see if that fixes the crash. Again, though, look at the error message to see specifically why the code is crashing, and that will lead you to the solution.

Well, you're not returning a valid value from your commented out code. What do you use 'dataColumn' for next? Running under the debugger should point you right to the issue, no?