Logging to a file on the iPhone

Question

What would be the best way to write log statements to a file or database in an iPhone application?

Ideally, NSLog() output could be redirected to a file using freop

Answer 1

If you want to use Cocoa, NSString and NSData have methods for reading/writing to file and NSFileManager gives you file operations. Here's an example (should work on iPhone):

NSData *dataToWrite = [[NSString stringWithString:@"String to write"] dataUsingEncoding:NSUTF8StringEncoding];

NSString *docsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
NSString *path = [docsDirectory stringByAppendingPathComponent:@"fileName.txt"];

// Write the file
[dataToWrite writeToFile:path atomically:YES];

// Read the file
NSString *stringFromFile = [[NSString alloc] initWithContentsOfFile:path];  

// Check if file exists
NSFileManager *fileManager = [NSFileManager defaultManager];
[fileManager fileExistsAtPath:path]; // Returns a BOOL    

// Remove the file
[fileManager removeItemAtPath:path error:NULL];

// Cleanup
[stringFromFile release];
[fileManager release];